Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
  • B05B17/0653—Details
  • B05B17/0661—Transducer materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
  • B05B17/0653—Details
  • B05B17/0676—Feeding means

Definitions

• the invention relates to the field of microacoustics and relates to a device for liquid atomization, as it can be used for example in the medical field for inhalation or in the technical field for cooling or the control of atmospheric conditions, but also for fuel injection or fragrance distribution or for micro-printing , and a method for its production.
• SAW surface acoustic waves
• Piezoelectric substrates with interdigital transducers (IDT) with apertures of 1 to 10 mm (overlapping area of the finger electrodes) were used as components at frequencies between 1 and 200 MHz.
• the substrates used were lithium niobate, aluminum nitride or zinc oxide.
• Liquids were sputtered, for example, water, alcohols, glycerol, oils, micro and nanoparticle solutions, cell solutions or protein solutions.
• the electrical control is carried out by frequency generators and amplifiers, continuously or in pulsed mode.
• the liquid is supplied in the region of the maximum amplitude of the particle oscillation, so that the current acoustic wave hits the liquid centrally ( K. Chono et al .: Jap. of Appl. Phys. Part 1 Regular Papers Short Notes & Review Papers 43, 2987 (2004 )). Also on components, which standing acoustic waves stimulate, the liquid supply is realized at this location ( J. Ju et al .: Sens. Actuator A-Phys. 147, 570 (2008 )). This positioning of the liquid supply in the region of the acoustic path is useful because the sputtering of the liquid is possible only at high amplitudes of the particle oscillation.
• the disadvantage is that there are secondary interactions between the SAW and the liquid volume and / or the fluid meniscus, such as fluid accumulation by increasing the contact angle to the Rayleigh angle and the fluid supply from the reservoir, to flow excitations ("acoustic streaming ", Eckart flow), for excitation of capillary waves at the liquid-gas interface to the separation of larger liquid droplets (jetting), which can reduce the efficiency of the sputtering process, destabilize the sputtering process and adversely affect the aerosol properties.
• a solution is known in which a transparent glass substrate has been used to create channel structures in the photoresist ( S. Tuomikoski and S. Franssila, Sensors and Actuators A 120 (2005) 408-415 ).
• the channel is made on all sides of the paint and thus the channel has no even contact with the substrate.
• the proposed solution requires more than one coating step, each with a subsequent exposure consisting of flood or structure exposures.
• a disadvantage of the known solutions as a whole is that corresponding microchannels can not be produced on an industrial scale and reliable and uniform atomization of liquids can not be guaranteed.
• Object of the present invention is to provide a device for liquid atomization, with the use of surface acoustic waves, a safe, reproducible and uniform atomization of liquids can be guaranteed, and further to provide a method for their preparation, which is easily reproducible and applicable on an industrial scale is.
• the liquid atomizing device consists of a piezoelectric substrate or of a substrate coated with a piezoelectric layer or of a non-piezoelectric substrate connected to a piezoelectric substrate via a coupling medium, wherein at least one interdigital transducer is provided on the piezoelectric substrate or on the substrate coated with a piezoelectric layer is applied with electrodes, and further on the piezoelectric substrate or on the substrate coated with a piezoelectric layer or on the coupled to the piezoelectric substrate via a coupling medium non-piezoelectric substrate one or more applied by photolithographic processes structures of polymer material with microchannels are present at least partially outside the propagation range of the acoustic wave or wave excited by the at least one interdigital transducer len, and the microchannels have at least two openings and at least one of the openings of the microchannels are arranged in the direction of the acoustic wave or waves, and this at least one opening of the microchannels is arranged at
• the piezoelectric substrate consists of monocrystalline SiO 2 , lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), langasite (La 3 Ga 5 SiO 14 ), Ca 3 TaGa 3 Si 2 O 14 , aluminum nitride (AlN), zinc oxide (ZnO) Lead zirconate titanate (PZT), lead magnesium niobate (PMN), gallium orthophosphate (GaPO 4 ) or a piezoelectric layer coated non-piezoelectric substrate of polymer, glass, ceramic or metal.
• the non-piezoelectric substrate connected to a piezoelectric substrate via a coupling medium consists of polymer, glass, ceramic or metal.
• the substrate on which the structures of polymeric material are optically transparent.
• microchannel one opening of which is located at the position where the amplitude of the acoustic wave or waves is 5-30%, more preferably 5-15% of the maximum amplitude of the wave or waves.
• microchannels are present, of which at least one opening is arranged at the position at which the amplitude of the acoustic wave or waves 5 - 30%, more preferably 5 - 15%, the maximum amplitude of the wave or waves is, wherein the microchannels are arranged on opposite sides of the acoustic wave on the substrate.
• microchannels are present, whose at least one opening is arranged on one or both sides of the acoustic wave or waves.
• the polymer material of the microchannels consists of epoxy-based polymeric photoresist, or novolak-based polymeric photoresist or acrylic-based polymeric photoresist.
• the cross sections of the microchannels are rectangular, square, semicircular or semi-oval, and / or a region of the circumference of the microchannels is formed by the substrate and / or layers located on the substrate.
• the inner walls of the microchannels are coated with single layers or multi-layer layers of metal material, silane compounds, polymer material, ceramic material or glass material.
• At least one opening of a microchannel is arranged at the position at which the increase in the amplitude of the acoustic wave or waves 10 -4 ... 10 nm / mm, advantageously 10 -3 ... 5 nm / mm, is.
• the contact angle of the liquid to the substrate surface or to a functional layer located on the substrate surface is less than or equal to the angle of the wave radiation into the liquid (Rayleigh angle).
• At least one interdigital transducer is applied to a piezoelectric substrate or to a substrate coated with a piezoelectric layer or to a substrate connected to a piezoelectric substrate via a coupling medium, then photolithographically patternable polymer material is applied and the structured one Exposure of the polymer material for producing one or more microchannels is carried out with at least two openings, wherein the structuring each one of the openings of the microchannels in the direction of the acoustic wave or waves is disposed at the position at which the acoustic wave or waves a demonstrable increase in the Amplitude of the acoustic wave or waves, and after the structured exposure and curing, the uncrosslinked polymer material is removed.
• photolithographically patternable polymer material with wavelength-dependent light absorption is applied and, to pattern the microchannels, first exposed to light of wavelength 1 for exposure of the microchannel walls and subsequently exposed to light of wavelength 2 for exposure of the microchannel cover.
• layers of dielectric or passivating material such as layers of SiO 2 , Al 2 O 3 , TiO 2 and / or metallic layers such as Al, Ti, Cr, Au, Pt, Pd applied.
• the inventive device for liquid atomization which essentially connects a SAW component with a polymeric, lithographically produced component and exploits the properties of an acoustic wave for the liquid atomization.
• the device consists of a substrate which can be used for a SAW component. These are piezoelectric substrates or substrates coated with a piezoelectric layer or a substrate connected to a piezoelectric substrate via a coupling medium.
• the latter substrates are referred to in the field of SAW fluid actuators as superstrates or over substrates.
• These may be, for example, non-piezoelectric glass, ceramic, metal or polymer plates, which are acoustically coupled to a piezoelectric substrate with a coupling medium.
• piezoelectric substrates it is possible to use all known piezoelectric substrate materials which are also known for SAW components and which enable excitation of Rayleigh or plate waves, such as monocrystalline SiO 2 , or LiNbO 3 (in particular 128 ° YX-LiNbO 3 ), LiTaO 3 , La 3 Ga 5 SiO 14 , Ca 3 TaGa 3 Si 2 O 14 , AlN, ZnO, lead zirconate titanate (PZT), lead magnesium niobate (PMN), gallium orthophosphate (GaPO 4 ) or coated polymer, glass, Ceramic or metal.
• monocrystalline SiO 2 or LiNbO 3 (in particular 128 ° YX-LiNbO 3 ), LiTaO 3 , La 3 Ga 5 SiO 14 , Ca 3 TaGa 3 Si 2 O 14 , AlN, ZnO, lead zirconate titanate (PZT), lead magnesium niobate (PMN), gallium orthophosphate (G
• At least one interdigital transducer with electrodes is applied to the substrates which can be used according to the invention, which are either piezoelectric substrates or are substrates coated with a piezo material. This is also done with known methods and materials from SAW technology, such as lift-off patterning methods and materials such as aluminum or titanium.
• SAW technology such as lift-off patterning methods and materials such as aluminum or titanium.
• only one interdigital transducer is applied to the substrate for a liquid atomization, but it is also possible to apply two or more interdigital transducers for a liquid atomization when standing wave fields or wave fields with a specific spatial structure or amplitude distribution are to be excited.
• one or more microchannels are present on the piezoelectric substrate or on the substrate coated with a piezoelectric material or on the non-piezoelectric substrate which is connected to a piezoelectric substrate via a coupling medium and which have been produced by means of photolithographic processes.
• photolithographically structurable polymer material is applied and subsequently there is a structured exposure of the polymer material for the production of one or more microchannels with at least two openings.
• Photolithographic polymer material are, for example, epoxy-based polymeric photoresists and / or novolak-based polymeric photoresists and / or acrylic-based polymeric photoresists such as SU-8, SU-850, SU-8-2000, SU-8-3000, KMPR, SPR 220-7, Ordyl P-50100 or Diaplate 132.
• the structured exposure of the polymer material is carried out, on the one hand, with chromium-structured masks or gray-shade masks provided with graduated intensity filters.
• the structured exposure can be performed in one process step.
• the photoresists can be structurally structured in three dimensions at the selected wavelength for the intransparency of the substrate. Therefore, it is advantageous for an industrial use to perform the structured exposure because of the far more favorable production of chromium-structured masks in two process steps.
• the respective structured exposures with respect to the wavelengths are to be adapted to the optical properties of the substrate and of the polymer materials. These are known criteria for photolithographic processes.
• Integrated methods that reduce or even completely prevent backscattering of UV light from the underside of the substrate or the substrate holder.
• This can be done for example by a functional coating with a Bragg reflector acting as a suitable layer system on the substrate surface.
• the layer acting as a Bragg reflector would thus mimic the positive reflection properties of Si substrates.
• the polymer material for producing the microchannel walls is exposed to light of a wavelength 1 and a photomask 1. It is important that at this chosen wavelength, the polymer material have a higher transparency and thus a lower optical density and at the same time the substrate have a lower reflectivity from the substrate bottom than in the subsequent exposure to light of a wavelength 2.
• the substrate in the Wavelength 1 either completely reflects the light from the surface or completely absorbs it.
• the already partially exposed polymer material is exposed again, but with light of a wavelength 2 and a photomask 2.
• the wavelength 2 is chosen so that the polymer material on exposure a high light absorption, ie a higher optical density compared to the light of wavelength 1.
• the entire volume of the polymer is exposed, but only an upper layer, which is thinner than the entire polymer layer.
• the second exposure is intended to produce the microchannel covers. After exposure, the annealing and thus the triggering of the desired chemical reactions for crosslinking and curing of the polymer material takes place.
• the following wet-chemical washing step with a paint developer removes the non-crosslinked polymer areas and thus exposes the channel structure.
• the bottom of the microchannels consists of the substrate material or the uppermost of the functional layers applied to the substrate material.
• the inner walls of the microchannel may be coated with various functional layers to produce a surface tension adapted to the fluid used. An adjusted surface tension can facilitate the filling of the channel.
• microchannels can be provided with functional layers of, for example, SiO 2 , Al 3 O 3 , TiO 2 , silane compounds for chemical functionalization, chemical passivation and / or adaptation of the wetting properties of the materials of the microchannels, for example by wet-chemical processes or gas-phase deposition.
• the remaining cured polymeric material has at least one microchannel, for example, having a rectangular cross-section with dimensions of 2000x50x50 ⁇ m 3 (length x height width).
• the positioning and orientation of the microchannels and their openings This is achieved by structured exposure and curing of the polymeric materials and subsequent removal of the uncured polymeric materials.
• the arrangement of the photolithographically structured polymer block with the microchannel or the microchannels on the substrate is at least partially outside the propagation range of the acoustic wave or waves, the orientation of the microchannel or the microchannels and their at least one opening in the direction of the acoustic wave or waves, advantageously at an angle of ⁇ 45 ° with respect to the orthogonal orientation of the opening to the propagation direction of the acoustic wave or waves, is also advantageously substantially orthogonal to the propagation direction of the acoustic wave or waves, and realized at least at a position relative to the acoustic wave or waves at which an increase in the amplitude of the acoustic wave or waves is detectable.
• the remaining microchannel part can be arranged outside the propagation range of the acoustic wave or waves.
• a plurality of microchannels may also be arranged on one or both sides of one or more acoustic waves, wherein at least one opening of a microchannel is always arranged at the position at which the amplitude of the acoustic wave or waves is 5-30% of the maximum amplitude the wave or waves is.
• the increase in the amplitude of the wave or waves is defined in the context of this invention such that in the presence of a trained wave or waves on a substrate, the wave or waves viewed over the cross section, from the substrate from both lateral edges of the wave from the amplitude to Amplitude maximum or more amplitude maxima increases.
• this location can be calculated.
• the location can also be determined by measuring the amplitude distribution given the structure and input signal, for example with the aid of a vibrometer.
• the position of the position can also be shifted on the substrate surface given a structure by increasing or decreasing the power supplied to the IDT so that at a fixed position on the substrate Substrate surface, the amount of increase in amplitude and the amplitude of the acoustic wave or waves can be changed.
• the position of the position may also be displaced on the substrate surface by increasing or decreasing the power supplied to the IDT so that at a fixed position on the substrate surface the magnitude of the amplitude increase and the amplitude of the acoustic wave or waves changed.
• the amount of increase in the amplitude of the acoustic wave or waves when using special IDT such as so-called chirped or slanted-finger IDT can be changed by changing the input electrical signals.
• chirped IDT by selecting the frequency in combination with the wavelength-dependent diffraction and wave propagation, a variation of the wave field, i. the spatial amplitude distribution can be achieved.
• the excitation of the SAW occurs at a frequency only in a part of the aperture, whereby the wave field can also be controlled accordingly.
• the at least second opening of the microchannels which is not arranged in the direction of the acoustic wave, is connected to a liquid reservoir.
• the microchannels advantageously have an L-shaped structure, wherein the shorter leg of the L is arranged in the direction of the liquid reservoir.
• There pumps, hoses or valves can be connected to ensure the supply of liquid.
• Other channel shapes, such as meanders, or channels with multiple channel openings, or the integration of active components such as pumps or valves into the microchannel are also possible.
• the dimensioning of the opening in the direction of the acoustic wave can be adapted to the dimensions of the desired liquid layer (width, height). It is also desirable to minimize the width of the microchannel walls in the interaction region with the acoustic wave in order to minimize the interactions of the polymer material with the acoustic wave and the intensity of disturbing effects, such as polymer heating and / or polymer degradation and / or the attenuation of the acoustic wave and / or to reduce the negative influence of the wave field.
• the width of the technologically feasible channel walls is limited by factors such as adhesive strength, mechanical stability and the limits of lithography in polymer layers.
• a spatial separation of liquid supply position and atomization zone is realized, which are interconnected by a thin film of liquid.
• the acoustic wave has little or no influence on its properties, secondary acoustic effects in the fluid are reduced and the best possible atomization of the liquid is possible.
• the polymer material is affected by the acoustic wave little or no negative, which results in a lower stress load and longer life and performance resistance of the polymer material.
• microchannels by photolithographic techniques are simple and inexpensive and easily applicable to mass production. It can be dispensed with expensive process steps, such as Waferbonden.
• the device according to the invention is easily miniaturized and can be well connected to higher-level fluid systems, such as pumps, reservoirs, valves.
• continuous or discontinuous liquid atomizations can be realized, both with only one liquid and with several different liquids, as well as a targeted control of the atomization at different locations by local change of the Increase in the amplitude of the acoustic wave or waves on the substrate.
• the atomization conditions can be controlled and thus the aerosol properties can be kept constant, for example with regard to the droplet size distribution, or else a selective aerosol formation or a time-variable aerosol formation can be realized.
• liquids are to be understood as meaning all liquids and also dispersions and suspensions with constituents in the nanometer range.
• an interdigital transducer made of 5nm titanium (as an adhesive layer) and resting 295nm aluminum by lift-off structuring.
• a 1 micron thick SiO 2 layer is applied as a functional layer by means of cathode sputtering.
• the SiO 2 layer is then etched free at the points of electrical contact.
• the interdigital transducer is of the quarter-wave type with finger and space widths of 15 ⁇ m each and an aperture of 2 mm.
• the surface of the substrate is cleaned by means of acetone and isopropyl alcohol under ultrasound for 10 min and subsequently blown off with nitrogen and treated with oxygen plasma.
• all particles and organic residues are removed from the surface, which improves the adhesion with the subsequently applied photoresist.
• 5 ml photoresist SU-8 50 is now dropped on the middle of the substrate.
• a paint layer on the surface of the substrate of about 80 microns thick is formed.
• the substrate with the lacquer layer is heated at a heating rate of 2 K / min to 95 ° C there held for 30 min and also cooled again at 2 K / min.
• the solvent is removed and tensions are minimized in the paint layer.
• the exposure process takes place.
• the exposure takes place in two steps, with the microchannel walls being structured in the first step and the microchannel cover in the second step.
• a photomask 1 is used in an exposure system operated in contact mode.
• the photomask 1 has structures of chrome and voids.
• the voids represent the areas to be exposed and thus the later microchannel walls.
• the photomask 1 is aligned in a device accordingly.
• the photoresist is exposed for a period of 20 s with a light dose of 7 mW / cm 2 .
• the second exposure is carried out with the photomask 2 at a wavelength of 254 nm with a light dose of 2 mW / cm 2 and an exposure time of 10 s.
• this photomask 2 has structures of chrome and voids, wherein the voids represent the areas to be exposed and thus the later manhole cover.
• the photomask 2 is also aligned in accordance with the previously exposed structures.
• a polymer block of 3.0 x 3.5 mm 2 (width x length) and a height of 80 ⁇ m remains.
• the L-shaped microchannel inside the polymer block has the dimensions of 1.5 mm length and 70x100 ⁇ m 2 (height width) of the long L-leg, which is parallel to the substrate surface and 80 ⁇ m in length and 100x100 ⁇ m 2 (height-width) of the short L -Schelskels, which is arranged at an angle of 90 ° to the substrate surface.
• the inner walls of the microchannel are coated with a 5 nm thick hydroxymethyltriethoxysilane layer to improve the wetting.
• the structured polymer block is located for the most part outside the path of the acoustic wave, with the opening of the long leg of the L-shaped microchannel being arranged perpendicular to the wave propagation direction.
• the channel opening is located in the propagation direction of the shaft at a distance of 3 mm from the IDT end and perpendicular to the propagation direction at a distance of 1.25 mm from the center of the aperture.
• the magnitude of the increasing amplitude of the SAW perpendicular to the propagation direction is approximately 4nm / mm, with nm (amplitude) and mm (distance on the substrate surface).
• the amplitude of the wave at the channel opening is only about 5% of the amplitude maximum at this distance to the IDT, whereby a very low energy input is ensured in the polymer material.
• interdigital transducer For electrical control of the interdigital transducer is a sine-wave generator, which is operated at the resonant frequency of the interdigital transducer (about 64MHz) and at the output of a 10W high-frequency amplifier is connected.
• the interdigital transducer is connected to the output via bonding wire bridges and SMA connection cables.
• the opening of the short leg of the L-shaped microchannel is connected via a rubber ring directly to a pressure plate with a liquid reservoir.
• a liquid reservoir When the liquid is added to the reservoir, it fills the channel and forms a fluid meniscus on the substrate surface at the opening of the long leg of the L-shaped microchannel.
• the liquid used is a 1% saline solution.
• the contact angle of the liquid to the SiO 2 is smaller than the Rayleigh angle.
• the interdigital transducer When a sine signal having the resonance frequency of the interdigital transducer and 4W electric power is applied, the interdigital transducer emits a Rayleigh-type surface acoustic wave.
• the surface acoustic wave reaches the location of the opening of the long leg of the L-shaped microchannel with the previously defined amplitude increase.
• a force is exerted on the liquid meniscus, it forms a thin layer of liquid and the liquid is drawn in the direction of the amplitude maximum.
• the atomization of the liquid takes place at the location of the amplitude maximum.
• a continuous liquid supply ensures continuous, uniform and reliable atomization.

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• 2014
  • 2014-11-06 DE DE102014222680.5A patent/DE102014222680A1/de not_active Ceased
• 2015
  • 2015-11-06 EP EP15193411.4A patent/EP3017876B1/fr active Active

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