CN113184803A - Magnetic nanoparticle self-assembly system based on magnetic field driving and processing method - Google Patents
Magnetic nanoparticle self-assembly system based on magnetic field driving and processing method Download PDFInfo
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- CN113184803A CN113184803A CN202110438556.9A CN202110438556A CN113184803A CN 113184803 A CN113184803 A CN 113184803A CN 202110438556 A CN202110438556 A CN 202110438556A CN 113184803 A CN113184803 A CN 113184803A
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Abstract
The invention discloses a magnetic-field-driven magnetic nanoparticle self-assembly-based system and a magnetic-field-driven magnetic nanoparticle self-assembly-based processing method, wherein the magnetic-field-driven magnetic nanoparticle self-assembly-based system comprises a silicon substrate, a groove structure is arranged on the silicon substrate, the groove structure comprises a first gold thin film and a second gold thin film, the first gold thin film is positioned on the second gold thin film, the first gold thin film and the second gold thin film are integrally formed, a plurality of nano soft magnets are nested in the second gold thin film in an array mode, a plurality of through grooves are formed in the first gold thin film, the through grooves and the nano soft magnets are arranged in a one-to-one correspondence mode, a microfluidic channel for flowing magnetic nanoparticle suspension liquid is arranged on the upper side of the groove structure, and bias magnetic fields are respectively arranged on the upper side of the microfluidic channel and the lower side of the silicon substrate. The invention promotes the self-assembly of the magnetic nano-particles to form a stable assembly structure under the action of an external bias magnetic field by means of the geometric constraint action of a specially designed groove structure and the action of high local strong magnetic dipole attraction force of the nano soft magnet.
Description
Technical Field
The invention relates to the field of magnetic field-driven magnetic nanoparticle self-assembly, in particular to a magnetic field-driven magnetic nanoparticle self-assembly-based system and a magnetic field-driven magnetic nanoparticle self-assembly-based processing method.
Background
With the development of nanotechnology, the method for preparing functionalized nanomaterial with regular structure based on bottom-up method has attracted people's attention since it has the characteristics of high production capacity and low cost. Among them, the method of driving the self-assembly of magnetic nanoparticles based on magnetic field is often used for synthesizing or designing functional materials and devices due to the characteristics of non-contact, instantaneity, anisotropy and the like of magnetic control.
However, the problem of poor uniformity of the self-assembly structure of the particles and low yield of the magnetic nanoparticles in terms of magnetic field control is still faced.
Disclosure of Invention
The invention aims to provide a magnetic-field-driven magnetic nanoparticle self-assembly system and a processing method, so as to overcome the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a system based on magnetic field drive magnetism nanoparticle self-assembly, includes the silicon substrate, is provided with groove structure on the silicon substrate, groove structure includes first gold film and second gold film, first gold film is located on the second gold film, and the two integrated into one piece, the inside array nestification that is of second gold film has a plurality of nanometer soft magnet, be provided with a plurality of grooves that run through on the first gold film, and run through groove and nanometer soft magnet one-to-one setting, the groove structure upside is provided with the microfluid passageway that is used for circulating magnetism nanoparticle suspension, the upside of microfluid passageway and the downside of silicon substrate are provided with bias magnetic field respectively.
Further, the nano soft magnet adopts permalloy, and the permalloy is composed of 78% of Fe and 22% of Ni in mass fraction.
Further, the center line of the through slot is aligned with the center line of the nano soft magnet.
Further, the bias magnetic field was generated by a cylindrical NdFeB permanent magnet having a diameter of 5cm and a height of 3 cm.
Further, the depth of the through groove is equal to the diameter of the magnetic nano particle.
Further, the depth of the microfluidic channel is 5 μm.
Further, the thickness of the nano soft magnet is 200nm, the thickness of the second gold thin film is 200nm, and the thickness of the first gold thin film is 100 nm.
Further, during the use process, when the particle assembly is carried out, the flow speed of the magnetic nanoparticle suspension in the microfluidic channel is 1mm/s, and the magnetic induction intensity B of the external bias magnetic field generated by the permanent magnet is BbiasIs 500 mT.
Further, when the particle assembly is completed, the flow rate of the magnetic nanoparticle suspension in the microfluidic channel is 50mm/s, and the magnetic induction intensity B of the external bias magnetic field generated by the permanent magnetbiasIs 100 mT.
A magnetic field driven magnetic nanoparticle self-assembly based system processing method comprises the steps of evaporating a layer of permalloy on a silicon substrate based on an electron beam evaporation technology, then carrying out spin coating, exposure and development, etching the permalloy by adopting an ion milling technology to form nano soft magnets arranged in an array, evaporating a layer of gold film around the nano soft magnets by adopting the electron beam evaporation technology, carrying out acetone ultrasonic stripping to obtain a groove structure, then obtaining a microfluidic channel by adopting an inductive coupling plasma etching technology and a micro-nano photoetching technology, and packaging the groove structure and the microfluidic channel by means of an oxygen plasma bonding technology.
Compared with the prior art, the invention has the following beneficial technical effects:
when the magnetic nano-particle self-assembly micro-fluid channel is used, magnetic nano-particle suspension with a certain concentration is injected into the micro-fluid channel at the initial moment, under the action of an external bias magnetic field, the magnetized nano soft magnet generates a highly localized strong gradient magnetic field area, magnetic nano-particles are driven to deposit on the surface of the nano soft magnet, and under the action of strong magnetic dipole contact force among the particles, the particles are self-assembled to form a complex three-dimensional stack structure.
Further, in order to improve the uniformity of the particle assembly structure, the invention can enhance the fluid viscosity acting on the particles by increasing the flow rate of the channel inlet, and drive the particles which are not confined in the grooves to leave the microfluidic channel along with the flow of the fluid, so that the nanoparticles confined in the through grooves form a stable assembly structure under the action of an external magnetic field.
Further, the thickness of the nano soft magnet and the depth of the through groove are consistent with the particle size of the magnetic nanoparticles, so that only a single layer of particles are deposited in the through groove; and the geometric dimension of the nano soft magnet and the through groove along the x-y plane has a certain integral multiple relation with the grain diameter of the magnetic nano particles so as to promote the number of the grains deposited in the through groove to be an integer.
Further, not only a magnetic field gradient region with nanometer accuracy is provided, but also by adjusting the flow rate of the inlet of the microfluidic channel, a nanoparticle assembly structure with high accuracy can be obtained. In addition, the nano soft magnet and the groove structure provided by the invention can be repeatedly used, so that the investment of experimental expenses is greatly reduced.
The processing method of the invention adopts the scheme of firstly evaporating permalloy and then evaporating a gold film, and can obtain the aligned nano soft magnet and groove structure only by a single glue spinning process, thereby omitting the complex processing process of multiple glue spinning and structure alignment, greatly simplifying the difficulty of the processing technology and improving the precision of the processing structure.
Drawings
FIG. 1 is a schematic diagram of a system for driving magnetic nanoparticle self-assembly based on magnetic field proposed in the present invention;
FIG. 2 is a schematic structural diagram of a nano-soft magnet and a groove array;
FIG. 3 is a micro-nano technology processing flow chart, wherein (a) is an evaporation Ni film; (b) spin-coating a photoresist; (c) direct writing by electron beams; (d) is developing; (e) etching for a metal etching machine; (f) plating non-magnetic material; (g) for peeling.
Wherein 1 is a silicon substrate; 2 is a nano soft magnet; 3 is a first gold film; 4 is a second gold film; and 5 is a microfluidic channel.
Detailed Description
Embodiments of the invention are described in further detail below:
referring to fig. 1 and 2, a magnetic field-driven magnetic nanoparticle self-assembly system includes a silicon substrate 1, a groove structure and a microfluidic channel 5, wherein the bottom of the microfluidic channel 5 is in direct contact with the groove structure, the groove structure includes a first gold thin film 3 and a second gold thin film 4, the first gold thin film 3 is located on the second gold thin film 4, and the first gold thin film and the second gold thin film are integrally formed, a plurality of nano soft magnets 2 are nested in the second gold thin film 4 in an array manner, a plurality of through grooves are formed in the first gold thin film 3, the through grooves and the nano soft magnets 2 are arranged in a one-to-one correspondence manner, the center lines of the through grooves are aligned with the center lines of the nano soft magnets 2, the depth of the through grooves is the same as the diameter of the magnetic nanoparticles, so that the movement space of the particles confined in the groove is greatly limited, and bias magnetic fields are respectively arranged on the upper side of the microfluidic channel 5 and the lower side of the silicon substrate 1, the bias magnetic field was generated by a cylindrical NdFeB permanent magnet, and the diameter of the cylindrical NdFeB permanent magnet was 5cm and the height was 3 cm.
The geometric structure of the nano soft magnet 2 is consistent with that of the through groove, the nano soft magnet 2 is of a cubic structure, a cylindrical structure or other three-dimensional structures, the material is permalloy and consists of 78% of Fe and 22% of Ni, the depth of the through groove is the same as the diameter of the magnetic nanoparticles, the thickness of the nano soft magnet 2 is 200nm, and when the cylindrical structure is adopted, the diameter is 300nm, so that a high-local strong gradient magnetic field area can be generated; the thickness of the second gold thin film 4 is 200nm, the thickness of the first gold thin film 3 is 100nm, and the sum of the thicknesses of the second gold thin film and the first gold thin film is 100nm thicker than that of the nano soft magnet and is used for restraining particles deposited on the surface of the magnet; the depth of the microfluidic channel 5 is5 μm, the flow velocity of the fluid is 1mm/s in the particle assembly process, and the magnetic induction intensity B of the bias magnetic field is appliedbiasIs 500mT, self-assembly of particles can be realized in 1min, the flow rate of the fluid is adjusted to 50mm/s after the self-assembly is finished, and bias magnetic induction intensity B is addedbiasAt 100mT, particles not deposited in the through trenches can be cleaned.
When the permalloy surface is etched by the ion milling technology, the included angle between the ion beam and the surface of the substrate is approximately vertical, so that the problem of secondary deposition of materials can be greatly weakened.
In addition, the invention realizes the processing of the nanometer soft magnet based on the micro-nano technology, which comprises the steps of evaporating a layer of permalloy on a silicon substrate based on the electron beam evaporation technology, then carrying out the steps of spin coating, exposure and development, etching the permalloy by adopting the ion milling technology to form a nanometer soft magnet array, wherein when the permalloy is etched by adopting the ion milling technology, the included angle between an ion beam and the surface of the substrate is approximately vertical, the problem of secondary deposition of the material can be greatly weakened, finally, evaporating a layer of gold film around the soft magnet by adopting the electron beam evaporation technology, finally carrying out ultrasonic stripping by acetone to obtain a groove structure, obtaining a microfluidic channel by adopting the inductive coupling plasma etching technology and the micro-nano photoetching technology, and packaging the nanometer soft magnet structure and the microfluidic channel by virtue of the oxygen plasma bonding technology.
The invention has the main points that the scheme of evaporating permalloy firstly and then evaporating a gold film is adopted, and the aligned nano soft magnet and groove structures can be obtained only through a single glue spinning process, so that the complex processing process of multiple glue spinning and structure alignment is omitted, the difficulty of the processing technology is greatly simplified, and the precision of the processing structure is improved;
the following examples are given to further illustrate the practice of the present invention:
the invention provides a system design for driving magnetic nano particle self-assembly by a microfluid-assisted soft magnet array and a processing scheme thereof. Fig. 1 is an integrated system of microfluidic channels and arrays of nano-soft magnets, comprising a silicon substrate 1, nano-soft magnets 2 arranged in an array, a second gold thin film 4 around the nano-soft magnets 2, a first gold thin film 3 on the second gold thin film 4, and microfluidic channels 5; the microfluidic channel 5 comprises an inlet and an outlet which are respectively used for injecting magnetic nanoparticle suspension and collecting waste liquid, the first gold film 3 is provided with a through groove corresponding to the nano soft magnet 2, the first gold film 3 and the second gold film 4 jointly form a groove structure, and the bottom of the microfluidic channel 5 is directly contacted with the groove structure. As shown in fig. 2, the geometry of the nano-soft magnet 2 is kept identical to the geometry of the through slot for constraining the geometrical area of the particle assembly structure.
As shown in FIG. 3, the processing of the nano soft-magnetic body and the fabrication of the groove structure are realized by only adopting a single-step glue spinning method in the processing of the nano soft-magnetic body unit. Firstly, adopting an electron beam evaporation technology to evaporate a permalloy (78% Fe + 22% Ni) with the thickness of 200nm on a silicon substrate 1 with the thickness of 1cm multiplied by 1cm, as shown in figure 3 (a); next, spin-coating a layer of photoresist with a thickness of 100nm on the surface of the permalloy by using a spin coater, as shown in fig. 3 (b); then, writing a pre-designed geometric pattern (such as a rectangular pattern according to the present invention) on the surface of the photoresist by using an electron beam direct writing technique, as shown in fig. 3 (c); after the pattern is written, developing by using a corresponding photoresist developer, and cleaning and drying, as shown in fig. 3 (d); next, the permalloy thin film is etched into nano soft magnet 2 of a corresponding pattern by using an ion milling technique, as shown in fig. 3 (e); then, evaporating a gold thin film with the thickness of 300nm around the nano soft magnet by adopting an electron beam evaporation technology, as shown in figure 3 (f); and finally, obtaining a nano soft magnet and a groove structure through ultrasonic stripping, finally obtaining a microfluidic channel through an inductive coupling plasma etching technology and a micro-nano photoetching technology, packaging the nano soft magnet structure and the microfluidic channel by means of an oxygen plasma bonding technology, injecting a magnetic nano particle suspension liquid through an inlet of the microfluidic channel when the nano soft magnet structure and the microfluidic channel are used, and realizing dynamic self-assembly of particles and improving the consistency of a particle assembly structure by utilizing the action of an external bias magnetic field.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. The utility model provides a system based on magnetic field drive magnetism nanoparticle self-assembly, its characterized in that includes silicon substrate (1), is provided with groove structure on silicon substrate (1), groove structure includes first golden film (3) and second golden film (4), first golden film (3) are located second golden film (4), and the two integrated into one piece, second golden film (4) inside is array nested has a plurality of nanometer soft magnet (2), be provided with a plurality of grooves that run through on first golden film (3), and run through groove and nanometer soft magnet (2) one-to-one setting, groove structure upside is provided with microfluid passageway (5) that are used for circulating magnetism nanoparticle suspension, the upside of microfluid passageway (5) and the downside of silicon substrate (1) are provided with bias magnetic field respectively.
2. A magnetic field driven magnetic nanoparticle self-assembly based system according to claim 1, characterized in that the nano-soft magnet (2) is permalloy, which consists of 78% Fe and 22% Ni in mass fraction.
3. A system for magnetic field driven magnetic nanoparticle self-assembly based on claim 1, wherein the center line of the through slot is aligned with the center line of the nano soft magnet (2).
4. The system of claim 1, wherein the bias magnetic field is generated by a cylindrical NdFeB permanent magnet having a diameter of 5cm and a height of 3 cm.
5. The system according to claim 1, wherein the depth of the through groove is equal to the diameter of the magnetic nanoparticle.
6. The magnetic field-driven magnetic nanoparticle self-assembly-based system according to claim 1, wherein the depth of the microfluidic channel (5) is 5 μm.
7. A system for magnetic field driven magnetic nanoparticle self-assembly as defined in claim 1, wherein the thickness of the nano-soft magnet (2) is 200nm, the thickness of the second gold thin film (4) is 200nm, and the thickness of the first gold thin film (3) is 100 nm.
8. The magnetic-field-driven magnetic nanoparticle self-assembly-based system according to claim 1, wherein during the use, when the particle assembly is performed, the flow rate of the magnetic nanoparticle suspension in the microfluidic channel (5) is 1mm/s, and the magnetic induction intensity B of the bias magnetic field generated by the permanent magnet is appliedbiasIs 500 mT.
9. The magnetic-field-driven magnetic nanoparticle self-assembly-based system according to claim 8, wherein when the particle assembly is completed, the flow rate of the magnetic nanoparticle suspension in the microfluidic channel (5) is 50mm/s, and the magnetic induction intensity B of the applied bias magnetic field generated by the permanent magnet is BbiasIs 100 mT.
10. A processing method of a magnetic nanoparticle self-assembly system based on magnetic field driving according to claim 1 is characterized in that a layer of permalloy is vapor-plated on a silicon substrate (1) based on an electron beam evaporation technology, then the permalloy is etched by adopting an ion milling technology after spin coating, exposure and development to form a nano soft magnet (2) arranged in an array, a layer of gold film is vapor-plated around the nano soft magnet (2) by adopting the electron beam evaporation technology, a groove structure is obtained after acetone ultrasonic stripping, then a micro-fluidic channel (5) is obtained by adopting an inductive coupling plasma etching technology and a micro-nano photoetching technology, and the groove structure and the micro-fluidic channel (5) are packaged by means of an oxygen plasma bonding technology.
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- 2021-04-22 CN CN202110438556.9A patent/CN113184803B/en active Active
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