EP2567291A1 - Method of topographical and electrical nanostructuration of a thin film of electret polymer and thin film of electret polymer obtained - Google Patents

Method of topographical and electrical nanostructuration of a thin film of electret polymer and thin film of electret polymer obtained

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Publication number
EP2567291A1
EP2567291A1 EP11723497A EP11723497A EP2567291A1 EP 2567291 A1 EP2567291 A1 EP 2567291A1 EP 11723497 A EP11723497 A EP 11723497A EP 11723497 A EP11723497 A EP 11723497A EP 2567291 A1 EP2567291 A1 EP 2567291A1
Authority
EP
European Patent Office
Prior art keywords
film
electret polymer
patterns
thin film
structuring
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP11723497A
Other languages
German (de)
French (fr)
Inventor
Laurence Ressier
Etienne Palleau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Centre National de la Recherche Scientifique CNRS
Institut National des Sciences Appliquees de Toulouse
Original Assignee
Centre National de la Recherche Scientifique CNRS
Institut National des Sciences Appliquees de Toulouse
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, Institut National des Sciences Appliquees de Toulouse filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP2567291A1 publication Critical patent/EP2567291A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C99/00—Subject matter not provided for in other groups of this subclass
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/0002—Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/16—Coating processes; Apparatus therefor

Definitions

  • the invention relates to a method of structuring a thin film of electret polymer and a thin film of electret polymer obtained by this method.
  • the invention relates to a method of topographic and electrical nano-structuring of a thin film of electret polymer and a thin film of electret polymer obtained by this method.
  • the process according to the invention can be described as an "electrical nano-printing" process.
  • topographical is used to describe what is relative to the relief of a surface.
  • the term “electret polymer” denotes any polymeric material capable of conserving, for at least a certain duration, for example from a few hours to several months, an electric polarization induced by an electric field, after cancellation of said electric field.
  • nanometric pattern denotes any topographic pattern in hollow or in relief of which at least one dimension is between 1 and 1000 nm.
  • the term “mold” denotes any matrix or tool that makes it possible to reproduce topographic patterns (hollow or raised) in a material.
  • the product obtained does not include nanometric topographic patterns with vertices and bottoms.
  • the inventors have determined, against all odds, that it is possible to obtain a thin film of electret polymer comprising both nanometric recessed patterns and having a specific electrostatic charge distribution.
  • the aim of the invention is to propose a process for structuring a thin film of electret polymer making it possible to structure said film both topographically and electrically.
  • a method according to the invention opens the way to many applications, for example in the field of micro / nanoelectronics, in particular for the integration of nano-objects in functional devices by electrostatic trapping of nano-objects in patterns. hollow nanoscale formed in an electret polymer film.
  • the invention also aims at providing a method of structuring a thin film of electret polymer for structuring said film both topographically and electrically using a single and same mold.
  • the invention aims to provide such a method whose implementation is simple, fast, parallel, and is compatible with the constraints of an industrial operation.
  • the invention relates to a method for structuring a thin film of electret polymer having a free surface, called a treated surface, and an opposite surface, called a rear face, in which:
  • a structuring surface comprising raised nanometric patterns, called structuring patterns, and formed of a conductive or semiconductive material, with at least a part of the treated surface of said electret polymer thin film,
  • nanometric patterns are formed in said electret polymer thin film, said formed nanometric patterns having vertices and bottoms, exerting a pressure of the structuring surface on the treated surface of said electret polymer thin film during a duration T 1?
  • an electrical voltage is applied between the said pattern structuring surface and the said rear face of the said electret polymer thin film, after the formation of the said nanometric patterns in the electret polymer thin film, for a duration T 2 adapted to induce a differential distribution of electrostatic charges between the vertices and the bottoms of the patterns formed, and
  • a fourth step the application of the electrical voltage is stopped and the mold is removed from the surface of said thin film of electret polymer.
  • a single and same mold makes it possible to produce, on surfaces of several cm 2 , a topographic nano-structuring of a thin film of electret polymer by the formation of nanometric topographic patterns having vertices and projections. backgrounds, as well as electrical nanostructuring, formed nanoscale patterns with a differential distribution of electrostatic charges between peaks and bottoms.
  • the nanometric patterns thus formed exhibit an electrostatic charge difference between the peaks and the bottoms of the patterns such that the surface potential measured at the bottom of the patterns is higher (in absolute value) than the surface potential measured at the vertices of the units.
  • This phenomenon is relatively unexpected because the electric potential imposed on the structuring surface of the mold is the same over the entire structuring surface of the mold, so there is a priori no reason for the patterns formed in the thin film of electret polymer have such a difference in electrostatic charges.
  • This preferential injection of charges at the bottom of the patterns is due to the locally greater electric field in the bottoms of the patterns formed than at the vertices of these, the thickness of the electret polymer thin film. being reduced in the bottoms of the patterns formed relative to the vertices.
  • the steps of the process according to the invention can be repeated to structure several thin films of electret polymer afterwards, by reusing the same mold a large number of times.
  • the use of a mold having nanometric patterns on large surfaces also makes it possible to structure these electret polymer films on surfaces of several cm 2 , by the same method.
  • the thin film of electret polymer is deposited on a substrate.
  • the substrate may be formed of any material capable of supporting the electret polymer thin film.
  • the substrate is formed of a conductive or semiconductor material.
  • the substrate may for example be silicon.
  • the material constituting the electret polymer thin film any electret polymeric material capable of being shaped can be used.
  • the electret polymer thin film is formed of an electret material chosen from thermoplastic polymers and thermosetting polymer materials.
  • the material constituting the electret polymer thin film is chosen from thermoplastic polymer materials.
  • said material constituting the thin film of electret polymer is chosen from polyacrylates, especially polymethyl methacrylates (PMMA), polypropylenes (PP), polystryrene (PS), polyvinyl chloride (PVC) polyvinyl alcohols (PVA), polyethylene terephthalate (PET), fluoropolymers such as polytetrafluoroethylenes (PTFE), and copolymers thereof.
  • PMMA polymethyl methacrylates
  • PP polypropylenes
  • PS polystryrene
  • PVC polyvinyl chloride
  • PVA polyvinyl alcohols
  • PET polyethylene terephthalate
  • fluoropolymers such as polytetrafluoroethylenes (PTFE), and copolymers thereof.
  • the electret polymer thin film is formed of a thermoplastic polymer material, and, in the second step, the mold structuring surface is pressurized on the treated surface of the electret polymer thin film, after the film has been heated to a temperature above the glass transition temperature (Tg) of said thermoplastic polymer material.
  • Tg glass transition temperature
  • all the elements are brought to a temperature greater than the glass transition temperature of the thermoplastic polymer material, that is to say the mold, the electret polymer thin film and the substrate, if appropriate.
  • the material constituting the electret polymer thin film is obtained from polymerizable monomers or prepolymers. These monomers or prepolymers may for example be chosen from the monomers or prepolymers of thermoset electrosulphide polymers or the monomers or prepolymers of thermoplastic polymers.
  • the structuring surface of the mold is then brought into contact with monomers or prepolymers, which may be in liquid form.
  • the monomers or prepolymers are polymerized under the effect of heat or any other energy source capable of allowing this polymerization, for example a source of ultraviolet (UV), during the exercise of the pressure. of the structuring surface of the mold on the treated surface of the electret polymer film.
  • UV ultraviolet
  • the pressure exerted by the structuring surface on the treated surface of the electret polymer thin film and the duration Ti during which the pressure is exerted are adapted according to the polymeric material forming the film.
  • the pressure can be applied by any means of applying a pressure known to those skilled in the art, adapted to the application of pressure in a method according to the invention.
  • the pressure exerted in the second step by the structuring surface on the treated surface of the electret polymer thin film is between 5 N and 5000 N, in particular between 500 N and 2000 N. pressure of the mold structuring surface on the treated surface of the electret polymer thin film is exerted for a predetermined time Ti of between 1 second and 2 hours.
  • the thickness of the electret polymer thin film depends on the intended applications.
  • the thickness of the electret polymer thin film is less than 5 mm, especially less than 1 mm, in particular less than 500 nm and more particularly less than 150 nm.
  • the mold used in a process according to the invention can be formed of any material compatible with the application of a pressure allowing the formation of nanometric patterns in the electret polymer thin film.
  • the mold must be formed of a more rigid material than the material forming the electret polymer thin film.
  • the mold has a structuring surface formed of a conductive or semiconductor material.
  • the mold is formed of a conductive or semiconductor material, in particular selected from silicon, N-doped silicon, for example phosphorus-doped silicon, P-doped silicon, for example boron doped silicon, and mixtures thereof.
  • the mold is formed of a non-conductive or weakly conductive material and only the structuring surface of the mold is formed of a conductive, semiconductor or more conductive material than the material forming the mold.
  • a thin metal layer may then for example be deposited on the structuring surface of the mold, by vacuum deposition or any other known method.
  • the structuring patterns can have any type of shape and size.
  • the patterns of structuring are formed of protuberances or indentations.
  • the reasons for structuring the mold may be uniformly distributed or not on the structuring surface.
  • the height of the structuring patterns represents the largest dimension between the bottoms and the vertices of each pattern.
  • the lateral dimension of a pattern pattern is the width at the base or top of the pattern.
  • the patterns of structuring of the mold have a height less than the thickness of the electret polymer thin film, so that the patterns formed in the electret polymer thin film are non-through and do not reach not the back side of the electret polymer thin film or the surface of the substrate, if any.
  • the patterns of structuring of the mold have a height ranging from 10 nm to 990 nm, in particular from 50 nm to 300 nm, and a lateral dimension ranging from 5 nm to 500 ⁇ m, in particular from 10 nm to 50 nm. ⁇ , and in particular from 3 ⁇ to ⁇ ⁇ .
  • a non-zero voltage of the same polarity is applied for a period T 2 between the structuring surface and the rear face of the electret polymer thin film.
  • Said electrical voltage can be applied by any suitable means to create a voltage of appropriate value between the structuring surface and the rear face of the electret polymer thin film.
  • To apply said electrical voltage it is sufficient for example to connect an electrically conductive portion of the mold forming said structuring surface and the substrate on which the electret polymer thin film is deposited to a voltage source and / or a current source.
  • said electrical voltage is applied between the structuring surface and the rear face of the electret polymer thin film by electrically connecting a first terminal of a voltage source to said surface. structuring the mold and a second terminal of said voltage source to said substrate.
  • an electrical voltage is imposed between the structuring surface and the rear face of the electret polymer thin film, and it is possible to measure an associated electric current and to deduce an internal resistance corresponding to the electret polymer thin film.
  • the said voltage is applied electrical connection between the pattern structuring surface and the back side of the electret polymer thin film by electrically connecting a first terminal of a current source to said mold patterning surface and a second terminal of said current source to said substrate.
  • a current is then set whose value is chosen so as to apply the desired electrical voltage between the structuring surface of the mold and the rear face of the electret polymer thin film, the value of this current depending on the internal resistance. corresponding to the thin film of electret polymer. It is also possible to combine these two variants.
  • the voltage applied in the third step may be continuous or in the form of pulses (pulses) of the same polarity.
  • the electric voltage applied in the third step of a method according to the invention may be of any non-zero value corresponding to the voltage values that can be applied by any electric generator and in particular adapted according to the material constituting the electret polymer thin film, in particular its breakdown voltage and its thickness.
  • a non-zero electrical voltage is applied between the structuring surface of the mold and the rear face of the electret polymer thin film of between -200 V and +200 V, in particular between -100 V and + 100 V, in particular between -50 V and + 50 V, and more particularly of the order of 25 V in absolute value.
  • a voltage source adapted to deliver said voltage is selected.
  • the source of current is chosen so that it delivers a current, suitable for forming said electrical voltage (according to the value of the internal resistance corresponding to the thin film of electret polymer), in particular between 1 mA. and 500 mA, and in particular of the order of 50 mA.
  • the electrical voltage is applied for a predetermined duration adapted to the formation of a difference in electrostatic charges between the vertices and the backgrounds of the patterns formed.
  • the electrical voltage can be applied from any moment, during the first step or during the second step for example. In other words, nothing prevents us from starting to apply an electrical voltage between the structuring surface and the rear face of the electret polymer film before the end of the second stage and the end of the pressure exertion by the structuring surface. on the treated surface of the electret polymer film.
  • the electrical voltage can be applied for a total duration, greater than or equal to T 2 , the total duration being greater than T 2 if one begins to apply an electrical voltage between the structuring surface and the rear face of the film before the end of the second step of a method according to the invention.
  • said electrical voltage is applied, after the formation of said nanometric patterns in the electret polymer thin film, for a duration T 2 of between 1 second and 1 hour. It has been found that in general the application of the voltage for a few minutes (T 2 ) is sufficient; for example, for a thin film of polymethyl methacrylate (PMMA) 130 nm thick, three minutes are enough.
  • the nanometric patterns formed in the thin film of electret polymer have, after cancellation of the applied electrical voltage, a non-zero electrical potential difference between the peaks and the grounds of the grounds between -5V and + 5V , especially between -2V and + 2V.
  • the electret polymer thin film obtained at the end of the fourth step is brought into contact with microobjects or nano-objects.
  • Micro-objects or nano-objects of any kind and any form can be used.
  • Micro-objects or nano-objects can be microparticles, nanoparticles, biological objects such as bacteria, viruses or proteins, or any other type of microsystems or nanosystems.
  • These micro-objects or nano-objects can be suspended in any type of fluid, gas or liquid, or in the form of powders.
  • Microparticles or nanoparticles may for example be in the form of tubes, son, rods, cubes, sea urchins or spheres.
  • said micro-objects and / or nano-objects are electrically charged or electrically polarizable (dipoles).
  • the electret polymer thin film obtained at the end of the fourth step is immersed in a colloidal solution of nanoparticles.
  • the invention extends to a thin film of electret polymer material obtained by a method according to the invention, characterized in that it comprises non-through nanometric patterns, having peaks and bottoms, and having a differential distribution of charges electrostatic between the tops and the grounds of the patterns.
  • the treated surface of the starting thin film is structured topographically and electrically.
  • the thin film obtained by a process according to the invention After being placed in contact with micro-objects and / or nano-objects, the thin film obtained by a process according to the invention has a differential distribution of the micro-objects and / or nano-objects between the vertices and the funds. nanometric patterns formed.
  • said thin film obtained by a method according to the invention is characterized in that micro-objects and / or nano-objects, in particular nanoparticles, are selectively disposed substantially only in the backgrounds. nanometric patterns formed.
  • the micro-objects and / or nano-objects are trapped electrostatically in said nanometric patterns formed.
  • Said micro-objects and / or nano-objects, and in particular said nanoparticles may be arranged in the bottoms of the nanometric patterns formed so as to form one or more continuous layers (s) or not.
  • the invention also relates to a method of nano-structuring a thin film of electret polymer, and a thin film of electret polymer material, characterized in combination by all or some of the characteristics mentioned above or below.
  • FIG. 1a is a schematic view illustrating the first step of a method according to the invention
  • FIG. 1b is a schematic view illustrating the second step of a method according to the invention.
  • FIG. 1a is a schematic view illustrating the third step of a method according to the invention.
  • FIG. 1d is a schematic view illustrating the fourth step of a method according to the invention.
  • FIG. 2 represents a three-dimensional topographic image, obtained by atomic force microscopy (AFM), of a portion of the structuring surface of a mold, bearing embossed patterns, used in a method according to the invention
  • FIG. 3 represents a topographic image, obtained by atomic force microscopy (AFM), of the same part as that represented in FIG. 2 of the structuring surface of a mold, bearing embossed patterns, used in a method according to the invention,
  • AFM atomic force microscopy
  • FIG. 4 is a graph showing the topographic profile of the structuring surface of a mold, along the dotted line marked on the image corresponding to FIG. 3, bearing embossed patterns, used in a method according to the invention,
  • FIG. 5 represents a topographic image, obtained by atomic force microscopy (AFM), of a part of the structured surface of a thin film of electret polymer obtained by a method according to the invention
  • FIG. 6 is a graph showing the topographic profile, along the dashed line marked on the image corresponding to FIG. 5, of the structured surface of a thin film of electret polymer obtained by a method according to the invention
  • FIG. 7 represents an image of the surface potential, obtained by Kelvin force microscopy (KFM), of the same part as that represented in FIG. 5 of the structured surface of a thin film of electret polymer obtained by a method according to FIG. 'invention
  • FIG. 8 is a graph showing the profile of the surface potential, along the dashed line marked on the image corresponding to FIG. 7, of a portion of the structured surface of an electret polymer thin film obtained by a process according to the invention,
  • FIG. 9 represents a topographic image, obtained by atomic force microscopy (AFM), of a portion of the structured surface of an electret polymer thin film obtained by a method according to the invention
  • FIG. 10 is a graph showing the topographic profile, along the line marked in dotted lines on the image corresponding to FIG. 9, of the structured surface of an electret polymer thin film obtained by a method according to the invention.
  • FIG. 11 represents an image of the surface potential obtained by Kelvin force microscopy (KFM), of the same part as that represented in FIG. 9 of the structured surface of an electret polymer thin film obtained by a method according to invention
  • FIG. 12 is a graph showing the profile of the surface potential, along the line marked in dashed lines on the image corresponding to FIG. 11, of a portion of the structured surface of a thin film of electret polymer obtained by a process according to the invention,
  • FIG. 13 represents a topographic image, obtained by atomic force microscopy (AFM), of a portion of the structured surface of an electret polymer thin film obtained by a method according to the invention, after contacting with nanoparticles, and
  • AFM atomic force microscopy
  • FIG. 14 represents a topographic image, obtained by atomic force microscopy (AFM), of the same part as that represented in FIG. 13 of the structured surface of an electret polymer thin film obtained by a method according to the invention, after contacting with nanoparticles.
  • the scales are not respected, and for illustrative purposes.
  • the darkest zones correspond to the lowest zones and the lightest zones correspond to the highest zones, the represented topographic amplitude being indicated at the top. above the corresponding gray scale.
  • FIGS. 7 and 11 relative to the surface potential, the darkest zones correspond to the zones having the lowest surface potential and the lightest zones correspond to the zones having a higher surface potential, the potential amplitude. surface shown being signaled above the corresponding gray level scale.
  • a machine 19 comprising a frame 20 is used to implement a method according to the invention.
  • the machine 19 comprises a fixed part 10 in which slides a piston 12 extended by a plate 13.
  • An adjustment means 11 makes it possible to adjust the pressure P exerted by a mold 2 on the free surface, called the treated surface 5 of a film 6 thin electret polymer.
  • a substrate 8, on which the electret polymer film 6 is deposited, is fixed, in particular by suction, to the plate 13 of the piston 12.
  • the fixed part 10 is extended by a support element 9.
  • the plate 13 is adapted to be able to exerting pressure on the substrate 8 of the electret polymer thin film 6 so as to exert mold pressure on the treated surface of the thin electret polymer film 6.
  • the mold 2 has a surface, called the structuring surface 4, comprising raised nanometric patterns 3, called structuring patterns, formed of protuberances.
  • the structuring surface 4 is formed of a conductive or semi-conductive material.
  • the mold 2 can be manufactured by a photolithography process followed by a wet etching step.
  • the mold 2 may be formed of a conductive or semiconductor material, in particular selected from silicon, N-doped silicon, for example phosphorus-doped silicon, P-doped silicon, for example boron-doped silicon, and mixtures thereof.
  • the mold 2 may be formed of a transparent material, in particular an ultraviolet-transparent material, allowing the use of a ultraviolet source for the polymerization of monomers or prepolymers for forming the thin film of electret polymer.
  • the mold 2 is disposed on the bottom 1 of the support member 9, the patterning surface 4 of the mold 2 being disposed on the side of the plate 13 of the piston.
  • the substrate 8 is fixed on the surface of the plate 13 disposed facing the mold 2 and so that the free surface, called the treated surface 5 of the film 6 deposited on the substrate 8 is arranged opposite the surface 4 of the structure of the mold.
  • the opposite surface of the film 6, called the back face 7, of the film is in contact with the substrate 8.
  • the structuring surface 4 is brought into contact with at least a portion of the planar treated surface of the thin electret polymer film 6 deposited on the substrate 8 made of conductive or semiconductive material.
  • the structuring patterns of the patterning surface 4 of the mold 2 have flat surfaces.
  • the vertices and the backgrounds of the structuring patterns have plane surfaces, each of the plane surfaces forming the vertices and each of the plane surfaces forming the bottoms of the structuring patterns are respectively located in the same plane.
  • the surfaces forming the bottoms of the patterns of structuring are preferably parallel to the surfaces forming the vertices of the patterns.
  • the structuring patterns can also take any form having bottoms and vertices.
  • the lateral spacing between the vertices and the backgrounds of the structuring patterns may be regular or not. The lateral spacing between the tops and the bottoms of the patterning units is advantageously adapted to obtain a difference in electrostatic charges between the peaks and the bottoms of the recessed patterns formed in the electret polymer thin film.
  • the invention is equally applicable in the case where the structuring patterns are recesses extending hollow in the mold.
  • the structuring surface 4 is pressed onto the treated surface of said thin electret polymer film 6, under conditions adapted to allow the formation of hollow nanometric patterns in the thin film of electret polymer.
  • the pressure exerted is adjusted using means 11 for adjusting the pressure exerted by the plate 13.
  • An enclosure 14 provided with means (s) for heating and means 15 for adjusting the temperature, such as a furnace 14 , is arranged to carry the mold 2, the substrate 8 and the thin film 6 of thermoplastic polymer at a temperature above the glass transition temperature of said thermoplastic polymer material forming the electret polymer thin film.
  • the oven 14 is disposed on a plate 16 fixed to the frame 20 of the machine 19 by means of fixing parts 17.
  • the furnace 14 is then removed so that the substrate 8, the thin electret polymer film 6 and the mold 2 reach a temperature below the glass transition temperature of the polymeric material forming the film 6.
  • the nanometric patterns are formed a the temperature of the electret polymer film is lower than the glass transition temperature in the case of a thermoplastic polymer and once the polymerization of the monomer is carried out in the case of a thermosetting polymer.
  • the nanometric patterns are likely to remain in shape once the mold removed.
  • a positive electrical voltage is applied, in the diagram shown, between said structuring surface 4 and said rear face of the film 6, that is to say between the structuring surface and the substrate 8, after the formation of said nanometric recessed patterns in the electret polymer thin film 6, for a predetermined duration T 2 adapted to induce a difference in electrostatic charges between the vertices and the grounds of the patterns.
  • the mold 2 is formed of a conductive material or semiconductor identical to the material forming the surface 4 of structuring of the mold. Electrical contacts are created in the mold 2 and the substrate 8 and connected to a voltage generator 18.
  • the entire structuring surface of the mold is electrically biased by an electrical voltage, the electrical potential of the surface of structuring of the mold being different from the electrical potential of the treated surface of the thin film of electret polymer.
  • a fourth step shown in FIG. 1d, the application of the electrical voltage is stopped and the mold 2 is removed from the surface of the thin film 6 of electret polymer. It can be seen that in this case, following the application of a positive electrical voltage, the nanoscale pattern bottoms formed in the electret polymer thin film are positively charged, very significantly, with respect to the top of the patterns.
  • FIG. 2 is a three-dimensional perspective topographic image, obtained by atomic force microscopy (AFM), of a part of the surface of this mold comprising the patterns of relief structuring.
  • FIG. 3 is a topographic image of this same mold, seen from the mold side, obtained by atomic force microscopy (AFM), having the patterns in relief, and
  • FIG. 4 is a graph representing the topographic profile of the structuring surface; of the mold along the segment shown in FIG.
  • a solution of polymethyl methacrylate (PMMA) is prepared by diluting PMMA granules in powder form, such as those sold by the company SIGMA ALDRICH (St. Louis, USA), with a molecular weight of the order of 15000 g / mole and whose glass transition temperature is 100 ° C, in methyl isobutyl ketone (MIBK) with a concentration of about 40 g / l.
  • the prepared PMMA solution is deposited on a P-doped silicon substrate (10 16 atoms / cm 3 ) of 1 cm side and 500 ⁇ thick, by spin-coating using a spinning wheel (acceleration: 5000 revolutions / min 2, speed: 2000 rpm for 30 seconds).
  • the silicon wafer is then placed on a hot plate so as to evaporate the MIBK solvent still present in the deposited PMMA film.
  • the PMMA thin film obtained, deposited on the silicon substrate has a thickness of 130 nm.
  • the mold is arranged facing the PMMA film supported by the silicon substrate and the assembly is heated to a temperature above the glass transition temperature of the PMMA, ie at 130 ° C. in an oven.
  • a mechanical pressure of the mold of 1000 N is then exerted on the treated surface of the PMMA film for 30 minutes, then the whole is cooled to a temperature of 50 ° C.
  • An electrical voltage of + 20 V is then applied, for a period of 3 minutes, between the structuring surface of the mold and the rear face of the film, the substrate being grounded.
  • An associated current of 50 mA was measured during the application of this voltage.
  • the mold is then removed.
  • a PMMA thin film comprising non-through through hollow nanometric patterns having a depth of 100 nm, and having a difference in electrostatic charges between the vertices and the bottoms of the formed hollow patterns.
  • the topography of the structured surface of the PMMA thin film obtained is shown in FIGS. 5 and 6, FIG. 6 representing the topographic profile of the structured surface along the dashed line drawn on the image corresponding to FIG. 5 (direction of said dotted line in abscissa and depth in ordinate).
  • the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns.
  • the hollow nanometric patterns formed in the PMMA film correspond to the negative patterning patterns of the mold used.
  • the hollow nanometric patterns formed in the PMMA film have a surface potential of the order of + 1800 mV with respect to the vertices of the patterns.
  • the surface potential of the structured surface of the PMMA thin film obtained is shown in FIGS. 7 and 8, FIG. 8 showing the profile of the potential of the structured surface along the dashed line marked on the image corresponding to FIG. 7 (direction of said dotted line in abscissa and potential on the ordinate).
  • the zero of the ordinate scale appreciably coincides with the level of the vertices of the patterns.
  • Example 2 In the same way as in Example 1, the same mold is used and a PMMA thin film is deposited in the same way on a silicon substrate but by applying an electric voltage of -50 V (instead of + 20 V). ). An associated current of 50 mA was measured during the application of this voltage.
  • a PMMA thin film is obtained with non-through-going recessed nanometric patterns having a depth of 100 nm, and having a difference in electrostatic charges between the vertices and the bottoms of the formed hollow patterns.
  • the topography of the structured surface of the PMMA thin film obtained is shown in FIGS. 9 and 10, FIG. 10 showing the topographic profile of the structured surface along the dashed line marked on the image corresponding to FIG. 9 (direction of said dotted line in abscissa and depth in ordinate).
  • the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns.
  • the hollow nanometric patterns formed in the PMMA film correspond to the negative patterning patterns of the mold used.
  • the hollow nanometric patterns formed in the PMMA film have a surface potential of the order of - 450 mV with respect to the vertices of the patterns.
  • the surface potential of the structured surface of the PMMA thin film obtained is represented in FIG. FIGS. 11 and 12, FIG. 12 representing the profile of the potential of the structured surface along the dashed line marked on the image corresponding to FIG. 11 (direction of said dotted line in abscissa and potential in ordinate).
  • the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns.
  • KFM Kelvin Force Microscope
  • the film prepared in Example 1 was immersed in a colloidal solution of latex nanoparticles (18x10 10 nanoparticles / ml) in isopropanol.
  • the latex nanoparticles used of spherical shape, have a size of 100 nm and are functionalized with negatively charged carboxyl functions. After immersion in this colloidal solution for one minute and then rinsing in isopropanol for 30 seconds, the film obtained is dried under a stream of nitrogen.
  • FIG. 14 corresponds to a zoom on the central part of the surface of the film represented in FIG. 13.
  • a PMMA thin film is thus obtained comprising non-through recessed nanometric patterns in which the latex nanoparticles are trapped electrostatically.
  • the surface of the PMMA thin film forming the top of the patterns has substantially no nanoparticles.
  • the invention may be subject to various variations and many other applications with respect to the embodiments and examples described above. It is for example possible to make patterns in the form of grooves from a mold having patterns in the form of lines of 200 nm in width, 100 nm in height and 2 ⁇ in length.

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Abstract

The invention relates to a method of nano-structuration of a thin film (6) of electret polymer, termed "electric nano-impression" method, in which a surface (4) of a mould (2), termed the structuration surface, comprising nanometric relief patterns (3), is placed in contact with at least one part of a free surface, termed the treated surface (5) of the thin film (6) of electret polymer, nanometric patterns are formed, corresponding to the negative of the structuration patterns of the mould, in said thin film (6) of electret polymer, by exerting a pressure of the structuration surface (4) on the surface (5) of the thin film (6) of electret polymer, an electric voltage is applied between said structuration surface (4) and the rear face (7) of the film (6) for a predetermined duration T2 suitable for inducing, after removal of the electric voltage applied, a differential distribution of electrostatic charges between the tops and the bottoms of the nanometric patterns formed in the thin electret polymer film.

Description

PROCÉDÉ DE NANO-STRUCTURATION TOPOGRAPHIQUE ET ÉLECTRIQUE D'UN FILM MINCE DE POLYMÈRE ÉLECTRET ET FILM  TOPOGRAPHIC AND ELECTRIC NANO-STRUCTURING METHOD OF ELECTRET POLYMER THIN FILM AND FILM
MINCE DE POLYMÈRE ÉLECTRET OBTENU  POLYMER THIN ELECTRET OBTAINED
L'invention concerne un procédé de structuration d'un film mince de polymère électret ainsi qu'un film mince de polymère électret obtenu par ce procédé.  The invention relates to a method of structuring a thin film of electret polymer and a thin film of electret polymer obtained by this method.
Plus particulièrement, l'invention concerne un procédé de nano-structuration topographique et électrique d'un film mince de polymère électret et un film mince de polymère électret obtenu par ce procédé. Le procédé selon l'invention peut être qualifié de procédé de « nano-impression électrique ».  More particularly, the invention relates to a method of topographic and electrical nano-structuring of a thin film of electret polymer and a thin film of electret polymer obtained by this method. The process according to the invention can be described as an "electrical nano-printing" process.
Dans tout le texte on désigne par « topographique » ce qui est relatif au relief d'une surface.  Throughout the text, "topographical" is used to describe what is relative to the relief of a surface.
Dans tout le texte on désigne par « polymère électret » tout matériau polymère susceptible de conserver, pendant au moins une certaine durée, par exemple de quelques heures à plusieurs mois, une polarisation électrique induite par un champ électrique, après annulation dudit champ électrique.  Throughout the text, the term "electret polymer" denotes any polymeric material capable of conserving, for at least a certain duration, for example from a few hours to several months, an electric polarization induced by an electric field, after cancellation of said electric field.
Dans tout le texte on désigne par « motif nanométrique » tout motif topographique en creux ou en relief dont au moins une dimension est comprise entre 1 et 1000 nm.  Throughout the text, the term "nanometric pattern" denotes any topographic pattern in hollow or in relief of which at least one dimension is between 1 and 1000 nm.
Dans tout le texte on désigne par « moule » toute matrice ou tout outil qui permet de reproduire des motifs topographiques (en creux ou en relief) dans un matériau.  Throughout the text, the term "mold" denotes any matrix or tool that makes it possible to reproduce topographic patterns (hollow or raised) in a material.
Les techniques de nanolithographie connues permettent de former des motifs en creux dans une couche mince de matériau polymère. En particulier, US 2004/0036201 décrit une technique de lithographie par nano- impression dans laquelle un moule présentant des motifs en relief est appliqué, grâce à une force électrostatique, sur une couche mince en matériau polymère déposée sur un substrat, de façon à transférer les motifs du moule en négatif dans une couche de matériau polymère. Le produit obtenu ne présente pas une répartition spatiale spécifique de charges électrostatiques. On connaît par ailleurs, une technique de tamponnage (« micro-contact printing ») électrique consistant à mettre en contact un tampon en matériau mou et conducteur comportant des motifs en relief, avec une surface plane d'un matériau électret, sans déformer plastiquement ce matériau électret, et à appliquer une différence de potentiel électrique entre le tampon et le substrat sur lequel est déposé le matériau électret de manière à former des zones distinctes chargées positivement ou négativement sur la surface du matériau électret. Le produit obtenu ne comporte pas de motifs topographiques nanométriques présentant des sommets et des fonds. Known nanolithography techniques make it possible to form recessed patterns in a thin layer of polymeric material. In particular, US 2004/0036201 describes a nano-printing lithography technique in which a mold having raised patterns is applied, by means of an electrostatic force, to a thin layer of polymer material deposited on a substrate, so as to transfer the negative mold patterns in a layer of polymeric material. The product obtained does not have a specific spatial distribution of electrostatic charges. Also known is an electrical "micro-contact printing" technique of contacting a pad of soft and conductive material comprising patterns in relief, with a flat surface of an electret material, without plastically deforming it. electret material, and to apply an electrical potential difference between the pad and the substrate on which the electret material is deposited so as to form distinct areas positively or negatively charged on the surface of the electret material. The product obtained does not include nanometric topographic patterns with vertices and bottoms.
Cependant, aucune technique connue de nano- structuration à la fois topographique et électrique d'un film mince de polymère électret n'a encore été décrite.  However, no known technique of both topographic and electrical nano-structuring of a thin film of electret polymer has yet been described.
Or les inventeurs ont déterminé, contre toute attente, qu'il est possible d'obtenir un film mince de polymère électret comportant à la fois des motifs nanométriques en creux et présentant une répartition de charges électrostatiques spécifique.  However, the inventors have determined, against all odds, that it is possible to obtain a thin film of electret polymer comprising both nanometric recessed patterns and having a specific electrostatic charge distribution.
L'invention vise à proposer un procédé de structuration d'un film mince de polymère électret permettant de structurer ledit film à la fois topographiquement et électriquement. Un procédé selon l'invention ouvre la voie à de nombreuses applications, par exemple dans le domaine de la micro/nano- électronique, notamment pour l'intégration de nano-objets dans des dispositifs fonctionnels par piégeage électrostatique de nano-objets dans des motifs nanométriques en creux formés dans un film de polymère électret.  The aim of the invention is to propose a process for structuring a thin film of electret polymer making it possible to structure said film both topographically and electrically. A method according to the invention opens the way to many applications, for example in the field of micro / nanoelectronics, in particular for the integration of nano-objects in functional devices by electrostatic trapping of nano-objects in patterns. hollow nanoscale formed in an electret polymer film.
L'invention vise également à proposer un procédé de structuration d'un film mince de polymère électret permettant de structurer ledit film à la fois topographiquement et électriquement à l'aide d'un unique et même moule.  The invention also aims at providing a method of structuring a thin film of electret polymer for structuring said film both topographically and electrically using a single and same mold.
L'invention vise à proposer un tel procédé dont la mise en œuvre est simple, rapide, parallèle, et est compatible avec les contraintes d'une exploitation industrielle. Pour ce faire, l'invention concerne un procédé de structuration d'un film mince de polymère électret présentant une surface libre, dite surface traitée, et une surface opposée, dite face arrière, dans lequel : The invention aims to provide such a method whose implementation is simple, fast, parallel, and is compatible with the constraints of an industrial operation. To this end, the invention relates to a method for structuring a thin film of electret polymer having a free surface, called a treated surface, and an opposite surface, called a rear face, in which:
- dans une première étape, on met en contact une surface d'un moule, dite surface de structuration, comportant des motifs nanométriques en relief, dits motifs de structuration, et formée en un matériau conducteur ou semiconducteur, avec au moins une partie de la surface traitée dudit film mince de polymère électret,  in a first step, contacting a surface of a mold, called a structuring surface, comprising raised nanometric patterns, called structuring patterns, and formed of a conductive or semiconductive material, with at least a part of the treated surface of said electret polymer thin film,
- dans une deuxième étape, on forme des motifs nanométriques dans ledit film mince de polymère électret, lesdits motifs nanométriques formés présentant des sommets et des fonds, en exerçant une pression de la surface de structuration sur la surface traitée dudit film mince de polymère électret pendant une durée T1? in a second step, nanometric patterns are formed in said electret polymer thin film, said formed nanometric patterns having vertices and bottoms, exerting a pressure of the structuring surface on the treated surface of said electret polymer thin film during a duration T 1?
caractérisé en ce que : characterized in that
- dans une troisième étape, on applique une tension électrique entre ladite surface de structuration du moule et ladite face arrière dudit film mince de polymère électret, après la formation desdits motifs nanométriques dans le film mince de polymère électret, pendant une durée T2 adaptée pour induire une répartition différentielle de charges électrostatiques entre les sommets et les fonds des motifs formés, et in a third step, an electrical voltage is applied between the said pattern structuring surface and the said rear face of the said electret polymer thin film, after the formation of the said nanometric patterns in the electret polymer thin film, for a duration T 2 adapted to induce a differential distribution of electrostatic charges between the vertices and the bottoms of the patterns formed, and
- dans une quatrième étape, on arrête l'application de la tension électrique et on retire le moule de la surface dudit film mince de polymère électret.  in a fourth step, the application of the electrical voltage is stopped and the mold is removed from the surface of said thin film of electret polymer.
Dans un procédé selon l'invention, un unique et même moule permet de réaliser, sur des surfaces de plusieurs cm2, une nano-structuration topographique d'un film mince de polymère électret par la formation de motifs topographiques nanométriques présentant des sommets et des fonds, ainsi qu'une nano-structuration électrique, les motifs nanométriques formés présentant une répartition différentielle de charges électrostatiques entre les sommets et les fonds. À l'issue de la quatrième étape, après annulation de la tension électrique appliquée, on constate que l'on obtient un film mince de polymère électret comportant des motifs topographiques nanométriques non traversants, présentant des sommets et des fonds, et présentant une différence de charge électrostatique (positive ou négative) entre les sommets et les fonds des motifs formés. En effet, les motifs nanométriques ainsi formés présentent une différence de charge électrostatique entre les sommets et les fonds des motifs telle que le potentiel de surface mesuré au fond des motifs est plus élevé (en valeur absolue) que le potentiel de surface mesuré aux sommets des motifs. Ce phénomène est relativement inattendu car le potentiel électrique imposé à la surface de structuration du moule est le même sur toute la surface de structuration du moule, il n'y a donc a priori pas de raison pour que les motifs formés dans le film mince de polymère électret présentent une telle différence de charges électrostatiques. Une explication possible de ce phénomène pourrait être que cette injection préférentielle de charges au fond des motifs est due au champ électrique localement plus important dans les fonds des motifs formés qu'aux sommets de ceux-ci, l'épaisseur du film mince de polymère électret étant réduite dans les fonds des motifs formés par rapport aux sommets. In a process according to the invention, a single and same mold makes it possible to produce, on surfaces of several cm 2 , a topographic nano-structuring of a thin film of electret polymer by the formation of nanometric topographic patterns having vertices and projections. backgrounds, as well as electrical nanostructuring, formed nanoscale patterns with a differential distribution of electrostatic charges between peaks and bottoms. At the end of the fourth step, after cancellation of the applied electrical voltage, it is found that a thin film of electret polymer having nanoscale non-traversing topographic patterns having peaks and funds, and having a difference in electrostatic charge (positive or negative) between the vertices and the backgrounds of the patterns formed. Indeed, the nanometric patterns thus formed exhibit an electrostatic charge difference between the peaks and the bottoms of the patterns such that the surface potential measured at the bottom of the patterns is higher (in absolute value) than the surface potential measured at the vertices of the units. reasons. This phenomenon is relatively unexpected because the electric potential imposed on the structuring surface of the mold is the same over the entire structuring surface of the mold, so there is a priori no reason for the patterns formed in the thin film of electret polymer have such a difference in electrostatic charges. One possible explanation for this phenomenon could be that this preferential injection of charges at the bottom of the patterns is due to the locally greater electric field in the bottoms of the patterns formed than at the vertices of these, the thickness of the electret polymer thin film. being reduced in the bottoms of the patterns formed relative to the vertices.
Avantageusement, les étapes du procédé selon l'invention peuvent être répétées pour structurer plusieurs films minces de polymère électret à la suite, en réutilisant le même moule un grand nombre de fois. L'utilisation d'un moule présentant des motifs nanométriques sur de grandes surfaces permet par ailleurs de structurer ces films de polymère électret sur des surfaces de plusieurs cm2, par le même procédé. Advantageously, the steps of the process according to the invention can be repeated to structure several thin films of electret polymer afterwards, by reusing the same mold a large number of times. The use of a mold having nanometric patterns on large surfaces also makes it possible to structure these electret polymer films on surfaces of several cm 2 , by the same method.
Avantageusement et selon l'invention, le film mince de polymère électret est déposé sur un substrat. Le substrat peut être formé en tout matériau susceptible de supporter le film mince de polymère électret. Avantageusement et selon l'invention, le substrat est formé en un matériau conducteur ou semi-conducteur. Le substrat peut par exemple être en silicium.  Advantageously and according to the invention, the thin film of electret polymer is deposited on a substrate. The substrate may be formed of any material capable of supporting the electret polymer thin film. Advantageously and according to the invention, the substrate is formed of a conductive or semiconductor material. The substrate may for example be silicon.
A titre de matériau constituant le film mince de polymère électret, on peut utiliser tout matériau polymère électret susceptible d'être mis en forme. Avantageusement et selon l'invention, le film mince de polymère électret est formé en un matériau électret choisi parmi les polymères thermoplastiques et les matériaux polymères thermodurcissables. Ainsi, dans une première variante, avantageusement et selon l'invention, le matériau constituant le film mince de polymère électret est choisi parmi les matériaux polymères thermoplastiques. Avantageusement et selon l'invention, ledit matériau constituant le film mince de polymère électret est choisi parmi les polyacrylates, notamment les polyméthacrylates de méthyle (PMMA), les polypropylènes (PP), les polystryrènes (PS), les polychlorures de vinyle (PVC), les alcools polyvinyliques (PVA), les polyéthylènes téréphtalate (PET), les fluoropolymères tels que les polytétrafluoroéthylènes (PTFE), et leurs copolymères. As the material constituting the electret polymer thin film, any electret polymeric material capable of being shaped can be used. Advantageously and according to the invention, the electret polymer thin film is formed of an electret material chosen from thermoplastic polymers and thermosetting polymer materials. Thus, in a first variant, advantageously and according to the invention, the material constituting the electret polymer thin film is chosen from thermoplastic polymer materials. Advantageously and according to the invention, said material constituting the thin film of electret polymer is chosen from polyacrylates, especially polymethyl methacrylates (PMMA), polypropylenes (PP), polystryrene (PS), polyvinyl chloride (PVC) polyvinyl alcohols (PVA), polyethylene terephthalate (PET), fluoropolymers such as polytetrafluoroethylenes (PTFE), and copolymers thereof.
Avantageusement et selon l'invention, le film mince de polymère électret est formé en un matériau polymère thermoplastique, et, dans la deuxième étape, on exerce une pression de la surface de structuration du moule sur la surface traitée du film mince de polymère électret, après que le film a été porté à une température supérieure à la température de transition vitreuse (Tg) dudit matériau polymère thermoplastique. De façon avantageuse l'ensemble des éléments est porté à une température supérieure à la température de transition vitreuse du matériau polymère thermoplastique, c'est-à-dire le moule, le film mince de polymère électret et le substrat, le cas échéant.  Advantageously and according to the invention, the electret polymer thin film is formed of a thermoplastic polymer material, and, in the second step, the mold structuring surface is pressurized on the treated surface of the electret polymer thin film, after the film has been heated to a temperature above the glass transition temperature (Tg) of said thermoplastic polymer material. Advantageously, all the elements are brought to a temperature greater than the glass transition temperature of the thermoplastic polymer material, that is to say the mold, the electret polymer thin film and the substrate, if appropriate.
Dans une autre variante de réalisation selon l'invention, le matériau constituant le film mince de polymère électret est obtenu à partir de monomères ou prépolymères polymérisables. Ces monomères ou prépolymères peuvent par exemple être choisis parmi les monomères ou prépolymères des polymères électrets thermodurcis sables ou les monomères ou prépolymères des polymères thermoplastiques. Dans la première étape, on met alors en contact la surface de structuration du moule avec des monomères ou prépolymères, pouvant se présenter sous forme liquide. Dans la deuxième étape, les monomères ou prépolymères sont polymérisés sous l'effet de la chaleur ou de toute autre source d'énergie susceptible de permettre cette polymérisation, par exemple une source d'ultraviolets (UV), pendant l'exercice de la pression de la surface de structuration du moule sur la surface traitée du film de polymère électret.  In another embodiment of the invention, the material constituting the electret polymer thin film is obtained from polymerizable monomers or prepolymers. These monomers or prepolymers may for example be chosen from the monomers or prepolymers of thermoset electrosulphide polymers or the monomers or prepolymers of thermoplastic polymers. In the first step, the structuring surface of the mold is then brought into contact with monomers or prepolymers, which may be in liquid form. In the second step, the monomers or prepolymers are polymerized under the effect of heat or any other energy source capable of allowing this polymerization, for example a source of ultraviolet (UV), during the exercise of the pressure. of the structuring surface of the mold on the treated surface of the electret polymer film.
La pression exercée par la surface de structuration sur la surface traitée du film mince de polymère électret et la durée Ti pendant laquelle la pression est exercée sont adaptées en fonction du matériau polymère formant le film. La pression peut être appliquée par tout moyen d'application d'une pression connu de l'homme du métier, adapté à l'application d'une pression dans un procédé selon l'invention. Avantageusement et selon l'invention, la pression exercée, dans la deuxième étape, par la surface de structuration sur la surface traitée du film mince de polymère électret, est comprise entre 5 N et 5000 N, notamment entre 500 N et 2000 N. La pression de la surface de structuration du moule sur la surface traitée du film mince de polymère électret est exercée pendant une durée prédéterminée Ti comprise entre 1 seconde et 2 heures. The pressure exerted by the structuring surface on the treated surface of the electret polymer thin film and the duration Ti during which the pressure is exerted are adapted according to the polymeric material forming the film. The pressure can be applied by any means of applying a pressure known to those skilled in the art, adapted to the application of pressure in a method according to the invention. Advantageously and according to the invention, the pressure exerted in the second step by the structuring surface on the treated surface of the electret polymer thin film is between 5 N and 5000 N, in particular between 500 N and 2000 N. pressure of the mold structuring surface on the treated surface of the electret polymer thin film is exerted for a predetermined time Ti of between 1 second and 2 hours.
L'épaisseur du film mince de polymère électret dépend des applications visées. Avantageusement et selon l'invention, l'épaisseur du film mince de polymère électret est inférieure à 5 mm, notamment inférieure à 1 mm, en particulier inférieure à 500 nm et plus particulièrement inférieure à 150 nm.  The thickness of the electret polymer thin film depends on the intended applications. Advantageously and according to the invention, the thickness of the electret polymer thin film is less than 5 mm, especially less than 1 mm, in particular less than 500 nm and more particularly less than 150 nm.
Le moule utilisé dans un procédé selon l'invention peut être formé en n'importe quel matériau compatible avec l'application d'une pression permettant la formation de motifs nanométriques dans le film mince de polymère électret. En particulier, le moule doit être formé en un matériau plus rigide que le matériau formant le film mince de polymère électret. En outre, avantageusement et selon l'invention, le moule présente une surface de structuration formée en un matériau conducteur ou semi-conducteur. En particulier, avantageusement et selon l'invention, le moule est formé d'un matériau conducteur ou semi-conducteur, notamment choisi parmi le silicium, le silicium dopé N, par exemple le silicium dopé au phosphore, le silicium dopé P, par exemple le silicium dopé au bore, et leurs mélanges. Dans une autre variante de réalisation, le moule est formé d'un matériau non conducteur ou faiblement conducteur et seule la surface de structuration du moule est formée d'un matériau conducteur, semi-conducteur ou plus conducteur que le matériau formant le moule. Une couche mince métallique peut alors par exemple être déposée sur la surface de structuration du moule, par dépôt sous vide ou toute autre méthode connue.  The mold used in a process according to the invention can be formed of any material compatible with the application of a pressure allowing the formation of nanometric patterns in the electret polymer thin film. In particular, the mold must be formed of a more rigid material than the material forming the electret polymer thin film. In addition, advantageously and according to the invention, the mold has a structuring surface formed of a conductive or semiconductor material. In particular, advantageously and according to the invention, the mold is formed of a conductive or semiconductor material, in particular selected from silicon, N-doped silicon, for example phosphorus-doped silicon, P-doped silicon, for example boron doped silicon, and mixtures thereof. In another alternative embodiment, the mold is formed of a non-conductive or weakly conductive material and only the structuring surface of the mold is formed of a conductive, semiconductor or more conductive material than the material forming the mold. A thin metal layer may then for example be deposited on the structuring surface of the mold, by vacuum deposition or any other known method.
Les motifs de structuration peuvent présenter tout type de forme et de taille. Les motifs de structuration sont formés de protubérances ou de renfoncements. Les motifs de structuration du moule peuvent être uniformément répartis ou non sur la surface de structuration. La hauteur des motifs de structuration représente la plus grande dimension entre les fonds et les sommets de chaque motif. La dimension latérale d'un motif de structuration correspond à la largeur à la base ou au sommet du motif. Avantageusement et selon l'invention, les motifs de structuration du moule présentent une hauteur inférieure à l'épaisseur du film mince de polymère électret, de façon à ce que les motifs formés dans le film mince de polymère électret soient non traversants et n'atteignent pas la face arrière du film mince de polymère électret ou la surface du substrat, le cas échéant. Avantageusement et selon l'invention, les motifs de structuration du moule présentent une hauteur allant de 10 nm à 990 nm, notamment de 50 nm à 300 nm, et une dimension latérale allant de 5 nm à 500 μπι, notamment de 10 nm à 50 μπι, et en particulier de 3 μπι à ΙΟ μπι. The structuring patterns can have any type of shape and size. The patterns of structuring are formed of protuberances or indentations. The reasons for structuring the mold may be uniformly distributed or not on the structuring surface. The height of the structuring patterns represents the largest dimension between the bottoms and the vertices of each pattern. The lateral dimension of a pattern pattern is the width at the base or top of the pattern. Advantageously and according to the invention, the patterns of structuring of the mold have a height less than the thickness of the electret polymer thin film, so that the patterns formed in the electret polymer thin film are non-through and do not reach not the back side of the electret polymer thin film or the surface of the substrate, if any. Advantageously and according to the invention, the patterns of structuring of the mold have a height ranging from 10 nm to 990 nm, in particular from 50 nm to 300 nm, and a lateral dimension ranging from 5 nm to 500 μm, in particular from 10 nm to 50 nm. μπι, and in particular from 3 μπι to ΙΟ μπι.
Avantageusement et selon l'invention, dans la troisième étape, on applique une tension électrique non nulle, de même polarité pendant une durée T2, entre la surface de structuration et la face arrière du film mince de polymère électret. Ladite tension électrique peut être appliquée par tout moyen adapté pour créer une tension électrique de valeur appropriée entre la surface de structuration et la face arrière du film mince de polymère électret. Pour appliquer ladite tension électrique, il suffit par exemple de relier une portion électriquement conductrice du moule formant ladite surface de structuration et le substrat sur lequel est déposé le film mince de polymère électret à une source de tension et/ou à une source de courant. Dans une première variante de réalisation d'un procédé selon l'invention, on applique ladite tension électrique entre la surface de structuration et la face arrière du film mince de polymère électret en reliant électriquement une première borne d'une source de tension à ladite surface de structuration du moule et une deuxième borne de ladite source de tension audit substrat. Dans ce cas, on impose une tension électrique entre la surface de structuration et la face arrière du film mince de polymère électret, et il est possible de mesurer un courant électrique associé et d'en déduire une résistance interne correspondante au film mince de polymère électret. Dans une deuxième variante, on applique ladite tension électrique entre la surface de structuration du moule et la face arrière du film mince de polymère électret en reliant électriquement une première borne d'une source de courant à ladite surface de structuration du moule et une deuxième borne de ladite source de courant audit substrat. Dans ce cas, on impose alors un courant dont on choisit la valeur de façon à appliquer la tension électrique souhaitée entre la surface de structuration du moule et la face arrière du film mince de polymère électret, la valeur de ce courant dépendant de la résistance interne correspondante au film mince de polymère électret. Il est également possible de combiner ces deux variantes de réalisation. Advantageously and according to the invention, in the third step, a non-zero voltage of the same polarity is applied for a period T 2 between the structuring surface and the rear face of the electret polymer thin film. Said electrical voltage can be applied by any suitable means to create a voltage of appropriate value between the structuring surface and the rear face of the electret polymer thin film. To apply said electrical voltage, it is sufficient for example to connect an electrically conductive portion of the mold forming said structuring surface and the substrate on which the electret polymer thin film is deposited to a voltage source and / or a current source. In a first variant embodiment of a method according to the invention, said electrical voltage is applied between the structuring surface and the rear face of the electret polymer thin film by electrically connecting a first terminal of a voltage source to said surface. structuring the mold and a second terminal of said voltage source to said substrate. In this case, an electrical voltage is imposed between the structuring surface and the rear face of the electret polymer thin film, and it is possible to measure an associated electric current and to deduce an internal resistance corresponding to the electret polymer thin film. . In a second variant, the said voltage is applied electrical connection between the pattern structuring surface and the back side of the electret polymer thin film by electrically connecting a first terminal of a current source to said mold patterning surface and a second terminal of said current source to said substrate. In this case, a current is then set whose value is chosen so as to apply the desired electrical voltage between the structuring surface of the mold and the rear face of the electret polymer thin film, the value of this current depending on the internal resistance. corresponding to the thin film of electret polymer. It is also possible to combine these two variants.
La tension électrique appliquée dans la troisième étape peut être continue ou sous forme d'impulsions (puises) de même polarité. La tension électrique appliquée dans la troisième étape d'un procédé selon l'invention peut être de toute valeur non nulle correspondant aux valeurs de tension pouvant être appliquées par tout générateur électrique et notamment adaptée en fonction du matériau constituant le film mince de polymère électret, notamment sa tension de claquage et son épaisseur.  The voltage applied in the third step may be continuous or in the form of pulses (pulses) of the same polarity. The electric voltage applied in the third step of a method according to the invention may be of any non-zero value corresponding to the voltage values that can be applied by any electric generator and in particular adapted according to the material constituting the electret polymer thin film, in particular its breakdown voltage and its thickness.
Avantageusement et selon l'invention, dans la troisième étape, on applique une tension électrique non nulle entre la surface de structuration du moule et la face arrière du film mince de polymère électret comprise entre - 200 V et + 200 V, notamment entre - 100 V et + 100 V, en particulier entre - 50 V et + 50 V, et plus particulièrement de l'ordre de 25 V en valeur absolue. Dans la première variante, on choisit une source de tension adaptée pour délivrer ladite tension électrique. Dans la deuxième variante, on choisit la source de courant de façon à ce qu'elle délivre un courant, propre à former ladite tension électrique (selon la valeur de la résistance interne correspondante au film mince de polymère électret), notamment compris entre 1 mA et 500 mA, et en particulier de l'ordre de 50 mA.  Advantageously and according to the invention, in the third step, a non-zero electrical voltage is applied between the structuring surface of the mold and the rear face of the electret polymer thin film of between -200 V and +200 V, in particular between -100 V and + 100 V, in particular between -50 V and + 50 V, and more particularly of the order of 25 V in absolute value. In the first variant, a voltage source adapted to deliver said voltage is selected. In the second variant, the source of current is chosen so that it delivers a current, suitable for forming said electrical voltage (according to the value of the internal resistance corresponding to the thin film of electret polymer), in particular between 1 mA. and 500 mA, and in particular of the order of 50 mA.
Dans la troisième étape, la tension électrique est appliquée pendant une durée prédéterminée adaptée à la formation d'une différence de charges électrostatiques entre les sommets et les fonds des motifs formés. La tension électrique peut être appliquée à partir de n'importe quel instant, au cours de la première étape ou au cours de la deuxième étape par exemple. Autrement dit, rien n'empêche de commencer à appliquer une tension électrique entre la surface de structuration et la face arrière du film de polymère électret avant la fin de la deuxième étape et la fin de l'exercice de la pression par la surface de structuration sur la surface traitée du film de polymère électret. La tension électrique peut être appliquée pendant une durée totale, supérieure ou égale à T2, la durée totale étant supérieure à T2 si on commence à appliquer une tension électrique entre la surface de structuration et la face arrière du film avant la fin de la deuxième étape d'un procédé selon l'invention. In the third step, the electrical voltage is applied for a predetermined duration adapted to the formation of a difference in electrostatic charges between the vertices and the backgrounds of the patterns formed. The electrical voltage can be applied from any moment, during the first step or during the second step for example. In other words, nothing prevents us from starting to apply an electrical voltage between the structuring surface and the rear face of the electret polymer film before the end of the second stage and the end of the pressure exertion by the structuring surface. on the treated surface of the electret polymer film. The electrical voltage can be applied for a total duration, greater than or equal to T 2 , the total duration being greater than T 2 if one begins to apply an electrical voltage between the structuring surface and the rear face of the film before the end of the second step of a method according to the invention.
Avantageusement et selon l'invention, dans la troisième étape, ladite tension électrique est appliquée, après la formation desdits motifs nanométriques dans le film mince de polymère électret, pendant une durée T2 comprise entre 1 seconde et 1 heure. Il a été constaté qu'en général l'application de la tension pendant quelques minutes (T2) suffit ; par exemple concernant un film mince de polyméthacrylate de méthyle (PMMA) de 130 nm d'épaisseur, trois minutes suffisent. Advantageously and according to the invention, in the third step, said electrical voltage is applied, after the formation of said nanometric patterns in the electret polymer thin film, for a duration T 2 of between 1 second and 1 hour. It has been found that in general the application of the voltage for a few minutes (T 2 ) is sufficient; for example, for a thin film of polymethyl methacrylate (PMMA) 130 nm thick, three minutes are enough.
Avantageusement et selon l'invention, les motifs nanométriques formés dans le film mince de polymère électret présentent, après annulation de la tension électrique appliquée, une différence de potentiel électrique non nulle entre les sommets et les fonds des motifs comprise entre -5V et +5V, notamment entre -2V et +2V.  Advantageously and according to the invention, the nanometric patterns formed in the thin film of electret polymer have, after cancellation of the applied electrical voltage, a non-zero electrical potential difference between the peaks and the grounds of the grounds between -5V and + 5V , especially between -2V and + 2V.
Avantageusement et selon l'invention, on met le film mince de polymère électret obtenu à l'issue de la quatrième étape en contact avec des microobjets ou des nano-objets. On peut utiliser des micro-objets ou des nano-objets de toute nature et de toute forme. Les micro-objets ou nano-objets peuvent être des microparticules, des nanoparticules, des objets biologiques tels que des bactéries, des virus ou encore des protéines, ou tous autres types de microsystèmes ou de nanosystèmes. Ces micro-objets ou nano-objets peuvent être en suspension dans tout type de fluide, gaz ou liquide, ou encore sous forme de poudres. Les microparticules ou nanoparticules peuvent par exemple se présenter sous forme de tubes, de fils, de bâtonnets, de cubes, d'oursins ou encore de sphères. Avantageusement et selon l'invention, lesdits micro-objets et/ou nano-objets sont chargés électriquement ou électriquement polarisables (dipôles). Advantageously and according to the invention, the electret polymer thin film obtained at the end of the fourth step is brought into contact with microobjects or nano-objects. Micro-objects or nano-objects of any kind and any form can be used. Micro-objects or nano-objects can be microparticles, nanoparticles, biological objects such as bacteria, viruses or proteins, or any other type of microsystems or nanosystems. These micro-objects or nano-objects can be suspended in any type of fluid, gas or liquid, or in the form of powders. Microparticles or nanoparticles may for example be in the form of tubes, son, rods, cubes, sea urchins or spheres. Advantageously and according to the invention, said micro-objects and / or nano-objects are electrically charged or electrically polarizable (dipoles).
Avantageusement et selon l'invention, on immerge le film mince de polymère électret obtenu à l'issue de la quatrième étape dans une solution colloïdale de nanoparticules.  Advantageously and according to the invention, the electret polymer thin film obtained at the end of the fourth step is immersed in a colloidal solution of nanoparticles.
L'invention s'étend à un film mince en matériau polymère électret obtenu par un procédé selon l'invention, caractérisé en ce qu'il comporte des motifs nanométriques non traversants, présentant des sommets et des fonds, et présentant une répartition différentielle de charges électrostatiques entre les sommets et les fonds des motifs. A l'issue d'un procédé selon l'invention, la surface traitée du film mince de départ est structurée topographiquement et électriquement.  The invention extends to a thin film of electret polymer material obtained by a method according to the invention, characterized in that it comprises non-through nanometric patterns, having peaks and bottoms, and having a differential distribution of charges electrostatic between the tops and the grounds of the patterns. At the end of a process according to the invention, the treated surface of the starting thin film is structured topographically and electrically.
Après avoir été mis en contact avec des micro-objets et/ou des nano-objets le film mince obtenu par un procédé selon l'invention présente une répartition différentielle des micro-objets et/ou des nano-objets entre les sommets et les fonds des motifs nanométriques formés. Avantageusement et selon l'invention, ledit film mince obtenu par un procédé selon l'invention est caractérisé en ce que des micro-objets et/ou des nano-objets, en particulier des nanoparticules, sont disposés de manière sélective sensiblement uniquement dans les fonds des motifs nanométriques formés.  After being placed in contact with micro-objects and / or nano-objects, the thin film obtained by a process according to the invention has a differential distribution of the micro-objects and / or nano-objects between the vertices and the funds. nanometric patterns formed. Advantageously and according to the invention, said thin film obtained by a method according to the invention is characterized in that micro-objects and / or nano-objects, in particular nanoparticles, are selectively disposed substantially only in the backgrounds. nanometric patterns formed.
Avantageusement et selon l'invention, les micro-objets et/ou nano-objets sont piégés électrostatiquement dans lesdits motifs nanométriques formés.  Advantageously and according to the invention, the micro-objects and / or nano-objects are trapped electrostatically in said nanometric patterns formed.
Lesdits micro-objets et/ou nano-objets, et en particulier lesdites nanoparticules, peuvent être disposés dans les fonds des motifs nanométriques formés de façon à constituer une ou plusieurs couches continue(s) ou non.  Said micro-objects and / or nano-objects, and in particular said nanoparticles, may be arranged in the bottoms of the nanometric patterns formed so as to form one or more continuous layers (s) or not.
L'invention concerne aussi un procédé de nano- structuration d'un film mince de polymère électret, et un film mince en matériau polymère électret, caractérisés en combinaison par tout ou partie des caractéristiques mentionnées ci-dessus ou ci-après. D'autres buts, avantages et caractéristiques de l'invention apparaissent à la lecture de la description des exemples qui suivent et qui se réfèrent aux figures annexées dans lesquelles : The invention also relates to a method of nano-structuring a thin film of electret polymer, and a thin film of electret polymer material, characterized in combination by all or some of the characteristics mentioned above or below. Other objects, advantages and characteristics of the invention appear on reading the description of the examples which follow and which refer to the appended figures in which:
- la figure la est une vue schématique illustrant la première étape d'un procédé selon l'invention,  FIG. 1a is a schematic view illustrating the first step of a method according to the invention,
- la figure lb est une vue schématique illustrant la deuxième étape d'un procédé selon l'invention,  FIG. 1b is a schematic view illustrating the second step of a method according to the invention,
- la figure le est une vue schématique illustrant la troisième étape d'un procédé selon l'invention,  FIG. 1a is a schematic view illustrating the third step of a method according to the invention,
- la figure ld, est une vue schématique illustrant la quatrième étape d'un procédé selon l'invention,  FIG. 1d is a schematic view illustrating the fourth step of a method according to the invention,
- la figure 2 représente une image topographique en trois dimensions, obtenue par microscopie à force atomique (AFM), d'une partie de la surface de structuration d'un moule, portant des motifs en relief, utilisé dans un procédé selon l'invention,  FIG. 2 represents a three-dimensional topographic image, obtained by atomic force microscopy (AFM), of a portion of the structuring surface of a mold, bearing embossed patterns, used in a method according to the invention; ,
- la figure 3 représente une image topographique, obtenue par microscopie à force atomique (AFM), de la même partie que celle représentée en figure 2 de la surface de structuration d'un moule, portant des motifs en relief, utilisé dans un procédé selon l'invention,  FIG. 3 represents a topographic image, obtained by atomic force microscopy (AFM), of the same part as that represented in FIG. 2 of the structuring surface of a mold, bearing embossed patterns, used in a method according to the invention,
- la figure 4 est un graphe représentant le profil topographique de la surface de structuration d'un moule, le long de la ligne en pointillés repérée sur l'image correspondant à la figure 3, portant des motifs en relief, utilisé dans un procédé selon l'invention,  FIG. 4 is a graph showing the topographic profile of the structuring surface of a mold, along the dotted line marked on the image corresponding to FIG. 3, bearing embossed patterns, used in a method according to the invention,
- la figure 5 représente une image topographique, obtenue par microscopie à force atomique (AFM), d'une partie de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 5 represents a topographic image, obtained by atomic force microscopy (AFM), of a part of the structured surface of a thin film of electret polymer obtained by a method according to the invention,
- la figure 6 est un graphe représentant le profil topographique, le long de la ligne en pointillés repérée sur l'image correspondant à la figure 5, de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention, - la figure 7 représente une image du potentiel de surface, obtenue par microscopie à force Kelvin (KFM), de la même partie que celle représentée en figure 5 de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention, FIG. 6 is a graph showing the topographic profile, along the dashed line marked on the image corresponding to FIG. 5, of the structured surface of a thin film of electret polymer obtained by a method according to the invention; , FIG. 7 represents an image of the surface potential, obtained by Kelvin force microscopy (KFM), of the same part as that represented in FIG. 5 of the structured surface of a thin film of electret polymer obtained by a method according to FIG. 'invention,
- la figure 8 est un graphe représentant le profil du potentiel de surface, le long de la ligne en pointillés repérée sur l'image correspondant à la figure 7, d'une partie de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 8 is a graph showing the profile of the surface potential, along the dashed line marked on the image corresponding to FIG. 7, of a portion of the structured surface of an electret polymer thin film obtained by a process according to the invention,
- la figure 9 représente une image topographique, obtenue par microscopie à force atomique (AFM), d'une partie de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 9 represents a topographic image, obtained by atomic force microscopy (AFM), of a portion of the structured surface of an electret polymer thin film obtained by a method according to the invention,
- la figure 10 est un graphe représentant le profil topographique, le long de la ligne repérée en pointillés sur l'image correspondant à la figure 9, de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 10 is a graph showing the topographic profile, along the line marked in dotted lines on the image corresponding to FIG. 9, of the structured surface of an electret polymer thin film obtained by a method according to the invention; ,
- la figure 11 représente une image du potentiel de surface obtenue par microscopie à force Kelvin (KFM), de la même partie que celle représentée en figure 9 de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 11 represents an image of the surface potential obtained by Kelvin force microscopy (KFM), of the same part as that represented in FIG. 9 of the structured surface of an electret polymer thin film obtained by a method according to invention,
- la figure 12 est un graphe représentant le profil du potentiel de surface, le long de la ligne repérée en pointillés sur l'image correspondant à la figure 11, d'une partie de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention,  FIG. 12 is a graph showing the profile of the surface potential, along the line marked in dashed lines on the image corresponding to FIG. 11, of a portion of the structured surface of a thin film of electret polymer obtained by a process according to the invention,
- la figure 13 représente une image topographique, obtenue par microscopie à force atomique (AFM), d'une partie de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention, après mise en contact avec des nanoparticules, et  FIG. 13 represents a topographic image, obtained by atomic force microscopy (AFM), of a portion of the structured surface of an electret polymer thin film obtained by a method according to the invention, after contacting with nanoparticles, and
- la figure 14 représente une image topographique, obtenue par microscopie à force atomique (AFM), de la même partie que celle représentée en figure 13 de la surface structurée d'un film mince de polymère électret obtenu par un procédé selon l'invention, après mise en contact avec des nanoparticules. Sur les figures la à ld, les échelles ne sont pas respectées, et ce à des fins d'illustration. Sur les figures 3, 5, 9, 13 et 14, représentant des images topographiques, les zones les plus foncées correspondent aux zones les plus basses et les zones les plus claires correspondent aux zones les plus hautes, l'amplitude topographique représentée étant signalée au-dessus de l'échelle de niveaux de gris correspondante. Sur les figures 7 et 11, relatives au potentiel de surface, les zones les plus foncées correspondent aux zones présentant le plus faible potentiel de surface et les zones les plus claires correspondent aux zones présentant un potentiel de surface plus élevé, l'amplitude de potentiel de surface représentée étant signalée au-dessus de l'échelle de niveaux de gris correspondante. FIG. 14 represents a topographic image, obtained by atomic force microscopy (AFM), of the same part as that represented in FIG. 13 of the structured surface of an electret polymer thin film obtained by a method according to the invention, after contacting with nanoparticles. In Figures la to ld, the scales are not respected, and for illustrative purposes. In FIGS. 3, 5, 9, 13 and 14, representing topographic images, the darkest zones correspond to the lowest zones and the lightest zones correspond to the highest zones, the represented topographic amplitude being indicated at the top. above the corresponding gray scale. In FIGS. 7 and 11, relative to the surface potential, the darkest zones correspond to the zones having the lowest surface potential and the lightest zones correspond to the zones having a higher surface potential, the potential amplitude. surface shown being signaled above the corresponding gray level scale.
Une machine 19 comportant un bâti 20 est utilisée pour mettre en œuvre un procédé selon l'invention. La machine 19 comprend une pièce fixe 10 dans laquelle coulisse un piston 12 prolongé par un plateau 13. Un moyen 11 de réglage permet de régler la pression P exercée par un moule 2 sur la surface libre, dite surface 5 traitée d'un film 6 mince de polymère électret. Un substrat 8, sur lequel est déposé le film 6 de polymère électret, est fixé, notamment par aspiration, au plateau 13 du piston 12. La pièce fixe 10 est prolongée d'un élément de support 9. Le plateau 13 est adapté pour pouvoir exercer une pression sur le substrat 8 du film 6 mince de polymère électret de manière à exercer une pression du moule sur la surface 5 traitée du film 6 mince de polymère électret.  A machine 19 comprising a frame 20 is used to implement a method according to the invention. The machine 19 comprises a fixed part 10 in which slides a piston 12 extended by a plate 13. An adjustment means 11 makes it possible to adjust the pressure P exerted by a mold 2 on the free surface, called the treated surface 5 of a film 6 thin electret polymer. A substrate 8, on which the electret polymer film 6 is deposited, is fixed, in particular by suction, to the plate 13 of the piston 12. The fixed part 10 is extended by a support element 9. The plate 13 is adapted to be able to exerting pressure on the substrate 8 of the electret polymer thin film 6 so as to exert mold pressure on the treated surface of the thin electret polymer film 6.
Le moule 2 présente une surface, dite surface 4 de structuration, comportant des motifs 3 nanométriques en relief, dits motifs de structuration, formés de protubérances. La surface 4 de structuration est formée en un matériau conducteur ou semi-conducteur. Le moule 2 peut être fabriqué par un procédé de photolithographie suivi d'une étape de gravure humide. Le moule 2 peut être formé en un matériau conducteur ou semi-conducteur, notamment choisi parmi le silicium, le silicium dopé N, par exemple le silicium dopé au phosphore, le silicium dopé P, par exemple le silicium dopé au bore, et leurs mélanges. Dans une autre variante de réalisation, le moule 2 peut être formé en un matériau transparent, notamment en un matériau transparent aux ultraviolets, permettant l'utilisation d'une source d'ultraviolets pour la polymérisation des monomères ou prépolymères destinés à former le film 6 mince de polymère électret. The mold 2 has a surface, called the structuring surface 4, comprising raised nanometric patterns 3, called structuring patterns, formed of protuberances. The structuring surface 4 is formed of a conductive or semi-conductive material. The mold 2 can be manufactured by a photolithography process followed by a wet etching step. The mold 2 may be formed of a conductive or semiconductor material, in particular selected from silicon, N-doped silicon, for example phosphorus-doped silicon, P-doped silicon, for example boron-doped silicon, and mixtures thereof. . In another variant embodiment, the mold 2 may be formed of a transparent material, in particular an ultraviolet-transparent material, allowing the use of a ultraviolet source for the polymerization of monomers or prepolymers for forming the thin film of electret polymer.
Le moule 2 est disposé sur le fond 1 de l'élément de support 9, la surface 4 de structuration du moule 2 étant disposée du côté du plateau 13 du piston. Le substrat 8 est fixé sur la surface du plateau 13 disposée en regard du moule 2 et de façon à ce que la surface libre, dite surface 5 traitée du film 6 déposé sur le substrat 8 soit disposée en regard de la surface 4 de structuration du moule. La surface opposée du film 6, dite face 7 arrière, du film est en contact avec le substrat 8.  The mold 2 is disposed on the bottom 1 of the support member 9, the patterning surface 4 of the mold 2 being disposed on the side of the plate 13 of the piston. The substrate 8 is fixed on the surface of the plate 13 disposed facing the mold 2 and so that the free surface, called the treated surface 5 of the film 6 deposited on the substrate 8 is arranged opposite the surface 4 of the structure of the mold. The opposite surface of the film 6, called the back face 7, of the film is in contact with the substrate 8.
Dans une première étape, représentée en figure la, on met en contact la surface 4 de structuration avec au moins une partie de la surface 5 traitée plane du film 6 mince de polymère électret déposé sur le substrat 8 en matériau conducteur ou semi-conducteur.  In a first step, shown in FIG. 1a, the structuring surface 4 is brought into contact with at least a portion of the planar treated surface of the thin electret polymer film 6 deposited on the substrate 8 made of conductive or semiconductive material.
Les motifs de structuration de la surface 4 de structuration du moule 2 présentent des surfaces planes. En particulier, les sommets et les fonds des motifs de structuration présentent des surfaces planes, chacune des surfaces planes formant les sommets et chacune des surfaces planes formant les fonds des motifs de structuration sont respectivement situées dans un même plan. De plus, les surfaces formant les fonds des motifs de structuration sont de préférence parallèles aux surfaces formant les sommets des motifs. Selon l'invention, les motifs de structuration peuvent également prendre toutes formes présentant des fonds et des sommets. D'autre part, l'espacement latéral entre les sommets et les fonds des motifs de structuration peut être régulier ou non. L'espacement latéral entre les sommets et les fonds des motifs de structuration est avantageusement adapté à l'obtention d'une différence de charges électrostatiques entre les sommets et les fonds des motifs en creux formés dans le film mince de polymère électret.  The structuring patterns of the patterning surface 4 of the mold 2 have flat surfaces. In particular, the vertices and the backgrounds of the structuring patterns have plane surfaces, each of the plane surfaces forming the vertices and each of the plane surfaces forming the bottoms of the structuring patterns are respectively located in the same plane. In addition, the surfaces forming the bottoms of the patterns of structuring are preferably parallel to the surfaces forming the vertices of the patterns. According to the invention, the structuring patterns can also take any form having bottoms and vertices. On the other hand, the lateral spacing between the vertices and the backgrounds of the structuring patterns may be regular or not. The lateral spacing between the tops and the bottoms of the patterning units is advantageously adapted to obtain a difference in electrostatic charges between the peaks and the bottoms of the recessed patterns formed in the electret polymer thin film.
L'invention s'applique aussi bien dans le cas où les motifs de structuration sont des renfoncements s'étendant en creux dans le moule.  The invention is equally applicable in the case where the structuring patterns are recesses extending hollow in the mold.
Dans une deuxième étape, représentée en figure lb, on exerce une pression de la surface 4 de structuration sur la surface 5 traitée dudit film 6 mince de polymère électret, dans des conditions adaptées pour permettre la formation de motifs nanométriques en creux dans le film 6 mince de polymère électret. La pression exercée est réglée à l'aide du moyen 11 de réglage de la pression exercée par le plateau 13. Une enceinte 14 muni de moyen(s) de chauffage et de moyen 15 de réglage de la température, tel qu'un four 14, est disposé de façon à porter le moule 2, le substrat 8 et le film 6 mince de polymère thermoplastique à une température supérieure à la température de transition vitreuse dudit matériau polymère thermoplastique formant le film mince de polymère électret. Avantageusement, le four 14 est disposé sur une plaque 16 fixée au bâti 20 de la machine 19 à l'aide de pièces 17 de fixation. In a second step, shown in FIG. 1b, the structuring surface 4 is pressed onto the treated surface of said thin electret polymer film 6, under conditions adapted to allow the formation of hollow nanometric patterns in the thin film of electret polymer. The pressure exerted is adjusted using means 11 for adjusting the pressure exerted by the plate 13. An enclosure 14 provided with means (s) for heating and means 15 for adjusting the temperature, such as a furnace 14 , is arranged to carry the mold 2, the substrate 8 and the thin film 6 of thermoplastic polymer at a temperature above the glass transition temperature of said thermoplastic polymer material forming the electret polymer thin film. Advantageously, the oven 14 is disposed on a plate 16 fixed to the frame 20 of the machine 19 by means of fixing parts 17.
Le four 14 est ensuite retiré de façon à ce que le substrat 8, le film 6 mince de polymère électret et le moule 2 atteignent une température inférieure à la température de transition vitreuse du matériau polymère formant le film 6. Les motifs nanométriques sont formés une fois que la température du film de polymère électret est inférieure à la température de transition vitreuse dans le cas d'un polymère thermoplastique et une fois la polymérisation du monomère effectuée dans le cas d'un polymère thermodurcissable. A l'issue de la deuxième étape, les motifs nanométriques sont donc susceptibles de rester en forme une fois le moule ôté.  The furnace 14 is then removed so that the substrate 8, the thin electret polymer film 6 and the mold 2 reach a temperature below the glass transition temperature of the polymeric material forming the film 6. The nanometric patterns are formed a the temperature of the electret polymer film is lower than the glass transition temperature in the case of a thermoplastic polymer and once the polymerization of the monomer is carried out in the case of a thermosetting polymer. At the end of the second step, the nanometric patterns are likely to remain in shape once the mold removed.
Dans une troisième étape, représentée en figure le, on applique une tension électrique positive, dans le schéma représenté, entre ladite surface 4 de structuration et ladite face arrière du film 6, c'est-à-dire entre la surface de structuration et le substrat 8, après la formation desdits motifs nanométriques en creux dans le film 6 mince de polymère électret, pendant une durée prédéterminée T2 adaptée pour induire une différence de charges électrostatiques entre les sommets et les fonds des motifs. Le moule 2 est formé en un matériau conducteur ou semiconducteur identique au matériau formant la surface 4 de structuration du moule. Des contacts électriques sont créés dans le moule 2 et le substrat 8 et reliés à un générateur 18 de tension électrique. In a third step, represented in FIG. 1c, a positive electrical voltage is applied, in the diagram shown, between said structuring surface 4 and said rear face of the film 6, that is to say between the structuring surface and the substrate 8, after the formation of said nanometric recessed patterns in the electret polymer thin film 6, for a predetermined duration T 2 adapted to induce a difference in electrostatic charges between the vertices and the grounds of the patterns. The mold 2 is formed of a conductive material or semiconductor identical to the material forming the surface 4 of structuring of the mold. Electrical contacts are created in the mold 2 and the substrate 8 and connected to a voltage generator 18.
Toute la surface de structuration du moule est polarisée électriquement par une tension électrique, le potentiel électrique de la surface de structuration du moule étant différent du potentiel électrique de la surface 5 traitée du film 6 mince de polymère électret. The entire structuring surface of the mold is electrically biased by an electrical voltage, the electrical potential of the surface of structuring of the mold being different from the electrical potential of the treated surface of the thin film of electret polymer.
Dans une quatrième étape, représentée en figure ld, on arrête l'application de la tension électrique et on retire le moule 2 de la surface du film 6 mince de polymère électret. On constate que dans ce cas, suite à l'application d'une tension électrique positive, les fonds des motifs nanométriques formés dans le film mince de polymère électret sont chargés positivement, de manière très significative, par rapport au sommet des motifs.  In a fourth step, shown in FIG. 1d, the application of the electrical voltage is stopped and the mold 2 is removed from the surface of the thin film 6 of electret polymer. It can be seen that in this case, following the application of a positive electrical voltage, the nanoscale pattern bottoms formed in the electret polymer thin film are positively charged, very significantly, with respect to the top of the patterns.
Exemple 1 : Préparation d'un film mince de polymère électret comportant des motifs nanométriques en creux non traversants et chargés positivement  EXAMPLE 1 Preparation of an Electret Polymer Thin Film Containing Non-Crossing and Positively Charged Nanoscale Recessed Patterns
Un moule constitué d'une plaquette de silicium dopé P (1018 atomes/cm3) de 5 mm de côté et de 275 μπι d'épaisseur, comportant des réseaux de motifs sous forme de plots carrés de 5 μπι de côté et 100 nm de hauteur est fabriqué par photolithographie et gravure humide. Dans chacun des réseaux de motifs, les motifs sont séparés par un espacement latéral de 5 μπι. La figure 2 est une image topographique en perspective et en trois dimensions, obtenue par microscopie à force atomique (AFM), d'une partie de la surface de ce moule comportant les motifs de structuration en relief. La figure 3 est une image topographique de ce même moule, vue du côté du moule, obtenue par microscopie à force atomique (AFM), présentant les motifs en relief, et la figure 4 est un graphe représentant le profil topographique de la surface de structuration du moule le long du segment représenté sur la figure 3. A mold consisting of a P-doped silicon wafer (10 18 atoms / cm 3 ) with a thickness of 5 mm and a thickness of 275 μπι, comprising pattern gratings in the form of 5 μπι square-shaped blocks and 100 nm height is manufactured by photolithography and wet etching. In each of the pattern arrays, the patterns are separated by a lateral spacing of 5 μπι. FIG. 2 is a three-dimensional perspective topographic image, obtained by atomic force microscopy (AFM), of a part of the surface of this mold comprising the patterns of relief structuring. FIG. 3 is a topographic image of this same mold, seen from the mold side, obtained by atomic force microscopy (AFM), having the patterns in relief, and FIG. 4 is a graph representing the topographic profile of the structuring surface; of the mold along the segment shown in FIG.
Une solution de polyméthacrylate de méthyle (PMMA) est préparée en diluant des granulés de PMMA sous forme de poudre, tels que ceux commercialisés par la société SIGMA ALDRICH (Saint-Louis, USA), de poids moléculaire de l'ordre de 15000 g/mole et dont la température de transition vitreuse est de 100 °C, dans du méthylisobutylcétone (MIBK) avec une concentration de l'ordre de 40 g/L. La solution de PMMA préparée est déposée sur un substrat en silicium dopé P (1016 atomes/cm3) de 1 cm de côté et de 500 μπι d'épaisseur, par spin-coating à l'aide d'une tournette (accélération : 5000 tours/min2, vitesse : 2000 tours/min pendant 30 secondes). La plaquette de silicium est ensuite placée sur une plaque chauffante de manière à évaporer le solvant MIBK encore présent dans le film de PMMA déposé. Le film mince de PMMA obtenu, déposé sur le substrat en silicium, possède une épaisseur de 130 nm. A solution of polymethyl methacrylate (PMMA) is prepared by diluting PMMA granules in powder form, such as those sold by the company SIGMA ALDRICH (St. Louis, USA), with a molecular weight of the order of 15000 g / mole and whose glass transition temperature is 100 ° C, in methyl isobutyl ketone (MIBK) with a concentration of about 40 g / l. The prepared PMMA solution is deposited on a P-doped silicon substrate (10 16 atoms / cm 3 ) of 1 cm side and 500 μπι thick, by spin-coating using a spinning wheel (acceleration: 5000 revolutions / min 2, speed: 2000 rpm for 30 seconds). The silicon wafer is then placed on a hot plate so as to evaporate the MIBK solvent still present in the deposited PMMA film. The PMMA thin film obtained, deposited on the silicon substrate, has a thickness of 130 nm.
Le moule est disposé en regard du film de PMMA supporté par le substrat en silicium et l'ensemble est porté à une température supérieure à la température de transition vitreuse du PMMA, soit à 130°C dans un four. Une pression mécanique du moule de 1000 N est alors exercée sur la surface traitée du film de PMMA pendant 30 minutes, puis l'ensemble est refroidi jusqu'à atteindre une température de 50 °C. Une tension électrique de + 20 V est ensuite appliquée, pendant une durée de 3 minutes, entre la surface de structuration du moule et la face arrière du film, le substrat étant mis à la masse. Un courant associé de 50 mA a été mesuré pendant l'application de cette tension. Le moule est ensuite ôté.  The mold is arranged facing the PMMA film supported by the silicon substrate and the assembly is heated to a temperature above the glass transition temperature of the PMMA, ie at 130 ° C. in an oven. A mechanical pressure of the mold of 1000 N is then exerted on the treated surface of the PMMA film for 30 minutes, then the whole is cooled to a temperature of 50 ° C. An electrical voltage of + 20 V is then applied, for a period of 3 minutes, between the structuring surface of the mold and the rear face of the film, the substrate being grounded. An associated current of 50 mA was measured during the application of this voltage. The mold is then removed.
On obtient un film mince de PMMA comportant des motifs nanométriques en creux non traversants d'une profondeur de 100 nm, et présentant une différence de charges électrostatiques entre les sommets et les fonds des motifs en creux formés. La topographie de la surface structurée du film mince de PMMA obtenue est représentée en figures 5 et 6, la figure 6 représentant le profil topographique de la surface structurée le long de la ligne en pointillés tracée sur l'image correspondant à la figure 5 (direction de ladite ligne en pointillés en abscisses et profondeur en ordonnées). Sur la figure 6 le zéro de l'échelle des ordonnées coïncide sensiblement avec le niveau des sommets des motifs. Les motifs nanométriques en creux formés dans le film de PMMA correspondent au négatif des motifs de structuration du moule utilisé. Les motifs nanométriques en creux formés dans le film de PMMA présentent un potentiel de surface de l'ordre de + 1800 mV par rapport aux sommets des motifs. Le potentiel de surface de la surface structurée du film mince de PMMA obtenue est représenté en figures 7 et 8, la figure 8 représentant le profil du potentiel de la surface structurée le long de la ligne en pointillés repérée sur l'image correspondant à la figure 7 (direction de ladite ligne en pointillés en abscisses et potentiel en ordonnées). Sur la figure 8 le zéro de l'échelle des ordonnées coïncide sensiblement avec le niveau des sommets des motifs. A PMMA thin film is obtained comprising non-through through hollow nanometric patterns having a depth of 100 nm, and having a difference in electrostatic charges between the vertices and the bottoms of the formed hollow patterns. The topography of the structured surface of the PMMA thin film obtained is shown in FIGS. 5 and 6, FIG. 6 representing the topographic profile of the structured surface along the dashed line drawn on the image corresponding to FIG. 5 (direction of said dotted line in abscissa and depth in ordinate). In Figure 6 the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns. The hollow nanometric patterns formed in the PMMA film correspond to the negative patterning patterns of the mold used. The hollow nanometric patterns formed in the PMMA film have a surface potential of the order of + 1800 mV with respect to the vertices of the patterns. The surface potential of the structured surface of the PMMA thin film obtained is shown in FIGS. 7 and 8, FIG. 8 showing the profile of the potential of the structured surface along the dashed line marked on the image corresponding to FIG. 7 (direction of said dotted line in abscissa and potential on the ordinate). In Figure 8 the zero of the ordinate scale appreciably coincides with the level of the vertices of the patterns.
En outre, les mêmes mesures au microscope à force Kelvin (KFM) ont été réalisées sur ce film notamment au bout de 24 heures et au bout de 3 mois, le film ayant été conservé à une température de 21°C et à pression atmosphérique (1013,25 hPa), en présence d'un taux d'humidité relative de l'air de l'ordre de 40%. Une diminution du potentiel de surface des motifs nano métriques de l'ordre de 50% a été observée au bout de 24 heures, puis, le potentiel de surface reste ensuite stable, le potentiel de surface mesuré 3 mois après étant sensiblement égal au potentiel de surface mesuré au bout de 24 heures.  In addition, the same measurements using a Kelvin Force Microscope (KFM) were carried out on this film, in particular after 24 hours and after 3 months, the film having been stored at a temperature of 21 ° C. and at atmospheric pressure ( 1013.25 hPa), in the presence of a relative humidity of the air of the order of 40%. A reduction in the surface potential of the nanometric units of the order of 50% was observed after 24 hours, then, the surface potential then remains stable, the surface potential measured 3 months after being substantially equal to the potential of surface measured after 24 hours.
Exemple 2 : Préparation d'un film mince de polymère électret comportant des motifs nanométriques en creux non traversants et chargés négativement  Example 2 Preparation of an Electret Polymer Thin Film Containing Non-Crossing and Negatively Charged Nanoscale Patterns
De la même manière que dans l'exemple 1 , on utilise le même moule et on dépose de la même manière un film mince de PMMA sur un substrat en silicium mais en appliquant une tension électrique de - 50 V (au lieu de + 20 V). Un courant associé de 50 mA a été mesuré pendant l'application de cette tension.  In the same way as in Example 1, the same mold is used and a PMMA thin film is deposited in the same way on a silicon substrate but by applying an electric voltage of -50 V (instead of + 20 V). ). An associated current of 50 mA was measured during the application of this voltage.
Après avoir ôté le moule, on obtient un film mince de PMMA comportant des motifs nanométriques en creux non traversants d'une profondeur de 100 nm, et présentant une différence de charges électrostatiques entre les sommets et les fonds des motifs en creux formés. La topographie de la surface structurée du film mince de PMMA obtenue est représentée en figures 9 et 10, la figure 10 représentant le profil topographique de la surface structurée le long de la ligne en pointillés repérée sur l'image correspondant à la figure 9 (direction de ladite ligne en pointillés en abscisses et profondeur en ordonnées). Sur la figure 10 le zéro de l'échelle des ordonnées coïncide sensiblement avec le niveau des sommets des motifs. Les motifs nanométriques en creux formés dans le film de PMMA correspondent au négatif des motifs de structuration du moule utilisé. Les motifs nanométriques en creux formés dans le film de PMMA présentent un potentiel de surface de l'ordre de - 450 mV par rapport aux sommets des motifs. Le potentiel de surface de la surface structurée du film mince de PMMA obtenue est représenté en figures 11 et 12, la figure 12 représentant le profil du potentiel de la surface structurée le long de la ligne en pointillés repérée sur l'image correspondant à la figure 11 (direction de ladite ligne en pointillés en abscisses et potentiel en ordonnées). Sur la figure 12 le zéro de l'échelle des ordonnées coïncide sensiblement avec le niveau des sommets des motifs. After removal of the mold, a PMMA thin film is obtained with non-through-going recessed nanometric patterns having a depth of 100 nm, and having a difference in electrostatic charges between the vertices and the bottoms of the formed hollow patterns. The topography of the structured surface of the PMMA thin film obtained is shown in FIGS. 9 and 10, FIG. 10 showing the topographic profile of the structured surface along the dashed line marked on the image corresponding to FIG. 9 (direction of said dotted line in abscissa and depth in ordinate). In Figure 10 the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns. The hollow nanometric patterns formed in the PMMA film correspond to the negative patterning patterns of the mold used. The hollow nanometric patterns formed in the PMMA film have a surface potential of the order of - 450 mV with respect to the vertices of the patterns. The surface potential of the structured surface of the PMMA thin film obtained is represented in FIG. FIGS. 11 and 12, FIG. 12 representing the profile of the potential of the structured surface along the dashed line marked on the image corresponding to FIG. 11 (direction of said dotted line in abscissa and potential in ordinate). In Figure 12 the zero of the ordinate scale coincides substantially with the level of the vertices of the patterns.
Les mesures au microscope à force Kelvin (KFM) ont été à nouveau réalisées sur le même film notamment au bout de 24 heures et au bout de 3 mois, le film ayant été conservé à une température de 21°C et à pression atmosphérique (1013,25 hPa), en présence d'un taux d'humidité relative de l'air de l'ordre de 40%. Une diminution du potentiel de surface (en valeur absolue) des motifs nanométriques de l'ordre de 50% a été observée au bout de 24 heures, puis, le potentiel de surface reste ensuite stable, le potentiel de surface mesuré 3 mois après étant sensiblement égal au potentiel de surface mesuré au bout de 24 heures.  Measurements using a Kelvin Force Microscope (KFM) were again performed on the same film, in particular after 24 hours and after 3 months, the film having been stored at a temperature of 21 ° C. and at atmospheric pressure (1013.degree. , 25 hPa), in the presence of a relative humidity of the air of the order of 40%. A decrease in the surface potential (in absolute value) of the nanometric units of the order of 50% was observed after 24 hours, then, the surface potential then remains stable, the surface potential measured 3 months later being substantially equal to the measured surface potential after 24 hours.
Exemple 3 : Préparation d'un film de polymère électret doté de nano-particules piégées dans des motifs nanométriques en creux  Example 3 Preparation of an Electret Polymer Film with Trapped Nano-particles in Hollow Nanometric Patterns
On immerge le film préparé dans l'exemple 1 dans une solution colloïdale de nanoparticules de latex (18xl010 nanoparticules/mL) dans de l'isopropanol. Les nanoparticules de latex utilisées, de forme sphérique, ont une taille de 100 nm et sont fonctionnalisées avec des fonctions carboxyles chargées négativement. Après une immersion dans cette solution colloïdale pendant une minute puis un rinçage dans de l'isopropanol pendant 30 secondes, le film obtenu est séché sous flux d'azote. The film prepared in Example 1 was immersed in a colloidal solution of latex nanoparticles (18x10 10 nanoparticles / ml) in isopropanol. The latex nanoparticles used, of spherical shape, have a size of 100 nm and are functionalized with negatively charged carboxyl functions. After immersion in this colloidal solution for one minute and then rinsing in isopropanol for 30 seconds, the film obtained is dried under a stream of nitrogen.
L'observation par microscopie à force atomique (AFM) de la surface du film obtenu (figures 13 et 14) révèle que les nanoparticules de latex se sont assemblées sélectivement au sein des motifs en creux formés dans la couche mince de PMMA, formant une couche de nanoparticules de latex dans les motifs en creux. La figure 14 correspond à un zoom sur la partie centrale de la surface du film représenté sur la figure 13. On obtient donc un film mince de PMMA comportant des motifs nanométriques en creux non traversants dans lesquels les nanoparticules de latex sont piégées électrostatiquement. La surface du film mince de PMMA formant le haut des motifs ne comporte sensiblement pas de nanoparticules. Par ailleurs, l'invention peut faire l'objet de diverses variantes et de nombreuses autres applications par rapport aux modes de réalisation et exemples décrits ci-dessus. Il est par exemple possible de réaliser des motifs sous forme de rainures à partir d'un moule présentant des motifs sous forme de lignes de 200 nm de largeur, 100 nm de hauteur et 2 μπι de longueur. Observation by atomic force microscopy (AFM) of the obtained film surface (FIGS. 13 and 14) reveals that the latex nanoparticles have selectively assembled within the hollow patterns formed in the thin layer of PMMA, forming a layer of latex nanoparticles in the recessed patterns. FIG. 14 corresponds to a zoom on the central part of the surface of the film represented in FIG. 13. A PMMA thin film is thus obtained comprising non-through recessed nanometric patterns in which the latex nanoparticles are trapped electrostatically. The surface of the PMMA thin film forming the top of the patterns has substantially no nanoparticles. Furthermore, the invention may be subject to various variations and many other applications with respect to the embodiments and examples described above. It is for example possible to make patterns in the form of grooves from a mold having patterns in the form of lines of 200 nm in width, 100 nm in height and 2 μπι in length.

Claims

REVENDICATIONS
1/ - Procédé de structuration d'un film (6) mince de polymère électret présentant une surface libre, dite surface (5) traitée, et une surface opposée, dite face (7) arrière, dans lequel :  1 / - A method of structuring a film (6) thin electret polymer having a free surface, said surface (5) treated, and an opposite surface, said face (7) rear, wherein:
- dans une première étape, on met en contact une surface d'un moule (2), dite surface (4) de structuration, comportant des motifs nanométriques en relief, dits motifs de structuration, et formée en un matériau conducteur ou semiconducteur, avec au moins une partie de la surface (5) traitée dudit film (6) mince de polymère électret,  in a first step, a surface of a mold (2), said structuring surface (4), is brought into contact with nanometric patterns in relief, called structuring patterns, and formed of a conductive or semiconductive material, with at least a portion of the treated surface (5) of said thin electret polymer film (6),
- dans une deuxième étape, on forme des motifs nanométriques dans ledit film (6) de polymère électret, lesdits motifs nanométriques formés présentant des sommets et des fonds, en exerçant une pression de la surface (4) de structuration sur la surface (5) traitée dudit film (6) mince de polymère électret pendant une durée T1? in a second step, nanometric patterns are formed in said electret polymer film (6), said formed nanometric patterns having vertices and bottoms, exerting a pressure of the structuring surface (4) on the surface (5) treated with said thin electret polymer film (6) for a duration T 1?
caractérisé en ce que : characterized in that
- dans une troisième étape, on applique une tension électrique entre ladite surface (4) de structuration du moule et ladite face (7) arrière dudit film (6) mince de polymère électret, après la formation desdits motifs nanométriques dans le film (6) mince de polymère électret, pendant une durée T2 adaptée pour induire une répartition différentielle de charges électrostatiques entre les sommets et les fonds des motifs formés, et in a third step, an electric voltage is applied between said mold structuring surface (4) and said rear face (7) of said thin electret polymer film (6), after the formation of said nanometric patterns in the film (6) thin electret polymer, for a duration T 2 adapted to induce a differential distribution of electrostatic charges between the vertices and the funds formed patterns, and
- dans une quatrième étape, on arrête l'application de la tension électrique et on retire le moule (2) de la surface dudit film (6) mince de polymère électret.  in a fourth step, the application of the electrical voltage is stopped and the mold (2) is removed from the surface of said thin electret polymer film (6).
21 - Procédé selon la revendication 1, caractérisée en ce que ledit film (6) mince de polymère électret est déposé sur un substrat (8).  21 - Process according to claim 1, characterized in that said thin film (6) of electret polymer is deposited on a substrate (8).
3/ - Procédé selon la revendication 2, caractérisé en ce que ledit substrat (8) est formé en un matériau conducteur ou semi-conducteur.  3 / - Method according to claim 2, characterized in that said substrate (8) is formed of a conductive or semiconductor material.
4/ - Procédé selon l'une des revendications 1 à 3, caractérisé en ce que ledit film (6) mince de polymère électret est formé en un matériau choisi parmi les matériaux polymères thermoplastiques et les matériaux polymères thermodurcissables. 5/ - Procédé selon l'une des revendications 1 à 4, caractérisé en ce que : 4 / - Method according to one of claims 1 to 3, characterized in that said film (6) thin electret polymer is formed of a material selected from thermoplastic polymer materials and thermosetting polymer materials. 5 / - Method according to one of claims 1 to 4, characterized in that:
- ledit film (6) mince de polymère électret est formé en un matériau polymère thermoplastique,  said thin electret polymer film (6) is formed of a thermoplastic polymer material,
- dans la deuxième étape, on exerce une pression de la surface (4) de structuration sur la surface (5) traitée dudit film (6) mince de polymère électret, après que le film (6) a été porté à une température supérieure à la température de transition vitreuse dudit matériau polymère thermoplastique.  in the second step, the structuring surface (4) is pressed on the treated surface (5) of said thin electret polymer film (6) after the film (6) has been heated to a temperature greater than the glass transition temperature of said thermoplastic polymer material.
6/ - Procédé selon l'une des revendications 1 à 5, caractérisé en ce que la pression exercée, dans la deuxième étape, par ladite surface (4) de structuration du moule sur la surface (5) traitée dudit film (6) mince de polymère électret, est comprise entre 5 N et 5000 N, notamment entre 500 N et 2000 N.  6 / - Method according to one of claims 1 to 5, characterized in that the pressure exerted, in the second step, by said surface (4) for structuring the mold on the treated surface (5) of said film (6) thin of electret polymer, is between 5 N and 5000 N, in particular between 500 N and 2000 N.
Il - Procédé selon l'une des revendications 1 à 6, caractérisé en ce que l'épaisseur dudit film (6) mince de polymère électret est inférieure à 5 mm, notamment inférieure à 1 mm, en particulier inférieure à 500 nm et plus particulièrement inférieure à 150 nm.  II - Process according to one of claims 1 to 6, characterized in that the thickness of said film (6) thin electret polymer is less than 5 mm, especially less than 1 mm, in particular less than 500 nm and more particularly less than 150 nm.
8/ - Procédé selon l'une des revendications 1 à 7, caractérisé en ce que le moule (2) est formé en un matériau choisi parmi les matériaux conducteurs et les matériaux semi-conducteurs.  8 / - Method according to one of claims 1 to 7, characterized in that the mold (2) is formed of a material selected from conductive materials and semiconductor materials.
91 - Procédé selon l'une des revendications 1 à 8, caractérisé en ce que le moule (2) est formé en un matériau choisi parmi le silicium, le silicium dopé N, par exemple le silicium dopé au phosphore, le silicium dopé P, par exemple le silicium dopé au bore, et leurs mélanges.  91 - Method according to one of claims 1 to 8, characterized in that the mold (2) is formed of a material selected from silicon, N-doped silicon, for example phosphorus-doped silicon, P-doped silicon, for example boron doped silicon, and mixtures thereof.
10/ - Procédé selon l'une des revendications 1 à 9, caractérisé en ce que les motifs de structuration du moule présentent une hauteur allant de 10 nm à 990 nm, notamment de 50 nm à 300 nm, et au moins une dimension latérale allant de 5 nm à 500 μπι, notamment de 10 nm à 50 μπι, en particulier de 3 μ ιη à 10 μιη .  10 / - Method according to one of claims 1 to 9, characterized in that the patterns of structuring of the mold have a height ranging from 10 nm to 990 nm, in particular from 50 nm to 300 nm, and at least one lateral dimension ranging from from 5 nm to 500 μπι, in particular from 10 nm to 50 μπι, in particular from 3 μ to 10 μιη.
11/ - Procédé selon l'une des revendications 1 à 10, caractérisé en ce que, dans la troisième étape, on applique une tension électrique non nulle entre la surface (4) de structuration du moule et la face (7) arrière du film (6) mince de polymère électret comprise entre - 200 V et + 200 V, notamment comprise entre - 100 V et + 100 V, en particulier entre - 50 V et + 50 V, et plus particulièrement de l'ordre de 25 V en valeur absolue. 11 / - Method according to one of claims 1 to 10, characterized in that, in the third step, a non-zero voltage is applied between the surface (4) for structuring the mold and the face (7) back of the film (6) thin electret polymer between -200 V and + 200 V, in particular between -100 V and + 100 V, in particular between -50 V and + 50 V, and more particularly of the order of 25 V in absolute value.
12/ - Procédé selon l'une des revendications 1 à 11, caractérisé en ce que, dans la troisième étape, ladite tension électrique est appliquée pendant une durée prédéterminée T2 comprise entre 1 seconde et 1 heure. 12 / - Method according to one of claims 1 to 11, characterized in that, in the third step, said voltage is applied for a predetermined duration T 2 between 1 second and 1 hour.
13/ - Procédé selon l'une des revendications 1 à 12, caractérisé en ce qu'on met ledit film (6) mince de polymère électret obtenu à l'issue de la quatrième étape en contact avec des micro-objets et/ou des nano-objets.  13 / - Method according to one of claims 1 to 12, characterized in that said thin film (6) electret polymer obtained at the end of the fourth step in contact with micro-objects and / or nano-objects.
14/ - Procédé selon la revendication 13, caractérisé en ce que lesdits micro-objets et/ou nano-objets sont chargés électriquement ou électriquement polarisables.  14 / - Method according to claim 13, characterized in that said micro-objects and / or nano-objects are electrically charged or electrically polarizable.
15/ - Procédé selon l'une des revendications 1 à 14, caractérisé en ce qu'on immerge ledit film (6) mince de polymère électret obtenu à l'issue de la quatrième étape dans une solution colloïdale de nanoparticules.  15 / - Method according to one of claims 1 to 14, characterized in that immerses said film (6) thin electret polymer obtained at the end of the fourth step in a colloidal solution of nanoparticles.
16/ - Film mince en matériau polymère électret obtenu par le procédé selon l'une des revendications 1 à 15, caractérisé en ce qu'il comporte des motifs nanométriques non traversants, présentant des sommets et des fonds, et une répartition différentielle de charges électrostatiques entre les sommets et les fonds des motifs.  16 / - thin film of electret polymer material obtained by the process according to one of claims 1 to 15, characterized in that it comprises non-through nanoscale patterns, having vertices and bottoms, and a differential distribution of electrostatic charges between the peaks and the grounds of the grounds.
17/ - Film mince selon la revendication 16, caractérisé en ce que des micro-objets et/ou des nano-objets, en particulier des nanoparticules, sont disposés essentiellement, et en particulier sélectivement uniquement, dans les fonds desdits motifs nanométriques formés.  17 / - thin film according to claim 16, characterized in that micro-objects and / or nano-objects, in particular nanoparticles, are arranged essentially, and in particular selectively only, in the bottoms of said nanometric patterns formed.
EP11723497A 2010-05-07 2011-04-22 Method of topographical and electrical nanostructuration of a thin film of electret polymer and thin film of electret polymer obtained Withdrawn EP2567291A1 (en)

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FR1001967A FR2959833B1 (en) 2010-05-07 2010-05-07 METHOD FOR TOPOGRAPHIC AND ELECTRIC NANO-STRUCTURE OF ELECTRONIC POLYMER THIN FILM AND ELECTRONIC POLYMER THIN FILM OBTAINED
US38483210P 2010-09-21 2010-09-21
PCT/FR2011/050934 WO2011138540A1 (en) 2010-05-07 2011-04-22 Method of topographical and electrical nanostructuration of a thin film of electret polymer and thin film of electret polymer obtained

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