Conductive film preparation device and method based on acoustical holography microfluidics

Abstract

The invention belongs to the field of acoustic flow control technologies and conductive composite materials, and particularly relates to a conductive film preparation device and method based on acoustic holography microfluidics, and conductive particles in a photosensitive solution are subjected to patterned arrangement by utilizing an acoustic holography sound field modulation technology; curing the photosensitive solution by using a curing lamp to form a conductive film; a photosensitive solution containing conductive particles is continuously introduced and cured based on a microfluidic technology, and a conductive film is pulled out, so that continuous preparation of the conductive film is realized.

Description

Technical Field

[0001] The present application relates to the fields of acoustofluidics and conductive composite materials, and in particular to a device and method for preparing a conductive film based on acoustic holographic microfluidics. Background Art

[0002] Conductive thin film-based strain sensors have enormous potential for applications in intelligent robotics, human-machine interfaces, intelligent health monitoring, and personalized healthcare monitoring systems. Due to the limitations of metals and semiconductors in sensitivity and elongation, conductive composites are being explored as alternatives. Conductive composites possess unique electrical, mechanical, and optical properties and typically consist of a polymer matrix with conductive particles dispersed within it. These particles typically take the form of various carbon or metal particles. Conventional methods for preparing conductive thin films include spin coating, roll coating, and spray coating. In these methods, the conductive particles are randomly distributed within the polymer matrix. Only when the particle concentration reaches the percolation threshold does a conductive pathway form within the polymer matrix. At high particle concentrations, the composite solution exhibits poor fluidity, and the cured film suffers from uneven resistance distribution, poor flexibility, and fragility. Previous studies have attempted to use external fields, such as magnetic, electric, and acoustic fields, to align the conductive particles in the pre-curing solution. This has resulted in cured films with high conductivity in specific directions at lower particle concentrations.

[0003] Existing methods for aligning conductive particles using external fields often suffer from various drawbacks. For example, magnetic field manipulation requires the particles to possess certain magnetic properties, limiting the types of particles available. When electric fields are used, dispersants present on the particle surface can alter the conductivity and dielectric constant of the polymer matrix solution, adversely affecting particle manipulation. In contrast, methods using acoustic fields to manipulate conductive particles primarily rely on the acoustic radiation force generated by sound waves radiating into the liquid. These methods offer advantages such as being label-free and less susceptible to external influences, and thus hold greater promise. Research has utilized bulk acoustic waves (BAW) or surface acoustic waves (SAW) to enrich and align conductive particles in microchambers, enabling the preparation of conductive composite materials with low filler concentrations. However, current devices for aligning conductive particles using acoustofluidics often rely on opposing piezoelectric transducers to generate a striped standing wave acoustic field, resulting in complex structures and high manufacturing precision requirements. For example, SAW-based particle alignment devices suffer from high electrode manufacturing costs and difficulty, as well as chip sensitivity to temperature. Influenced by the piezoelectric effect, the AC electric field generated by the vibration of the piezoelectric substrate in the control area can adversely affect the alignment of high-aspect-ratio conductive particles. BAW-based particle alignment devices have disadvantages such as high requirements for matching the acoustic wavelength with the chamber size, difficulty in chip manufacturing, and difficulty in integration. Furthermore, conductive films currently fabricated using acoustic fields to manipulate the alignment of conductive particles are typically discontinuously formed and small in size, hindering their widespread application in flexible sensing.

[0004] Based on the above problems, it is necessary to design a device and method that is simple in device, stable in performance, easy to adjust, low in cost and can achieve continuous preparation of conductive films. Summary of the Invention

[0005] The embodiments of the present application provide a device and method for preparing a conductive film based on acoustic holographic microfluidics, which fully considers the characteristics of conductive particles, utilizes the advantages of uniformity and stability of acoustic holographic sound field modulation, and the simplicity and detachability of the device, and combines it with microfluidics technology to achieve continuous, stable, efficient and low-cost preparation of conductive films.

[0006] To this end, according to one aspect of the present application, a conductive film preparation device based on acoustic holography microfluidics is provided, comprising an acoustic holography sound field modulation module, an ultrasonic dispersion injection module, a film pulling module, a connecting pipe, and a curing lamp; the acoustic holography sound field modulation module comprises an acoustic holography chip and an acoustic wave excitation device disposed at the bottom of the acoustic holography chip; the ultrasonic dispersion injection module comprises an injection pump and an ultrasonic dispersion syringe; the film pulling module comprises a winding roller and a pre-cured film connected to the winding roller at one end; The acoustic holographic chip includes an acoustic mask layer, a connecting layer and a microchannel layer arranged in sequence from bottom to top; the acoustic mask layer is provided with a groove microstructure with an isosceles trapezoidal cross section for modulating a striped standing wave sound field; the connecting layer is provided with a convex microstructure complementary to the groove microstructure for conducting sound waves and interlayer bonding; a photosensitive solution flow channel and a photosensitive solution chamber that are interconnected are provided between the microchannel layer and the connecting layer, the horizontal orientation of the convex microstructure is located within the boundary of the photosensitive solution chamber, and a protrusion is provided on the microchannel layer that is away from the photosensitive solution flow channel. The photosensitive solution injection port is connected to one end of the photosensitive solution chamber, the ultrasonic dispersion syringe is connected to the photosensitive solution injection port through the connecting tube, the ultrasonic dispersion syringe is used to inject a photosensitive solution mixed with conductive particles into the photosensitive solution injection port, the microchannel layer is also provided with a notch connected to the end of the photosensitive solution chamber away from the photosensitive solution flow channel, the notch is used for inserting the end of the pre-cured film away from the winding roller into the photosensitive solution chamber, and the curing lamp is used to cure the photosensitive solution in contact with the pre-cured film.

[0007] Optionally, the lower surface of the microchannel layer is provided with a positioning groove connected to the notch and extending toward the protruding microstructure, and a spacing is provided between the positioning groove and the protruding microstructure. The end of the pre-cured film away from the winding roller can be inserted into the positioning groove through the notch, and the curing lamp is located above the acoustic holographic chip. The irradiation area of ​​the curing lamp is a strip, the long side of which is parallel to the width direction of the photosensitive solution chamber and greater than the width of the photosensitive solution chamber, and the short side is greater than the spacing between the positioning groove and the protruding microstructure.

[0008] Optionally, the acoustic wave excitation device is a lead zirconate titanate piezoelectric transducer, and the lead zirconate titanate piezoelectric transducer is connected to the bottom of the acoustic mask layer at a position corresponding to the groove microstructure via a coupling liquid.

[0009] Optionally, in the groove microstructure, the upper base length of the isosceles trapezoid is 60 μm-100 μm, the lower base length is 500 μm, and the height is 170 μm-220 μm.

[0010] Optionally, the diameter of the photosensitive solution injection port is 2 mm, the width of the photosensitive solution flow channel is 1 mm, and the height is 200 μm; the width of the photosensitive solution chamber is 15 mm, and the height is 200 μm; the photosensitive solution flow channel and the photosensitive solution chamber are transitioned at an oblique angle, and the angle between the oblique angle and the channel is 30°-45°.

[0011] Optionally, the microchannel layer and the connecting layer are both made of polydimethylsiloxane, the microchannel layer is prepared by a soft photolithography process, and the connecting layer is prepared by pouring polydimethylsiloxane on the acoustic mask layer through a mold; the contact surface between the microchannel layer and the connecting layer is bonded at room temperature by oxygen plasma treatment.

[0012] Optionally, the thickness of the connecting layer is 30 μm-80 μm.

[0013] Optionally, the parameters of the groove microstructure are calculated by an iterative angular spectrum method; the calculation process includes the following steps: 1. drawing a binary amplitude diagram of the target stripe sound field; 2. calculating the angular spectrum of the target plane sound field; 3. back-propagating the angular spectrum to the surface of the sound mask and calculating the complex sound pressure distribution; 4. retaining the phase of the sound field on the surface of the sound mask and resetting the amplitude; 5. calculating the angular spectrum of the sound mask surface after reset and forward transmitting it to the target plane; 6. calculating the sound field distribution of the target plane after transmission, comparing the error with the design value, and iteratively calculating.

[0014] According to another aspect of the present application, a method for preparing a conductive film based on acoustic holographic microfluidics is provided. Based on the conductive film preparation device described above, the conductive film preparation method includes the following steps: Step 1: preparing a photosensitive solution containing conductive particles, and storing the photosensitive solution in the ultrasonic dispersion syringe; Step 2: preparing a pre-cured film, adhering one end of the prepared pre-cured film to the winding roller, and inserting the other end into the photosensitive solution chamber through the notch; Step 3: Turn on the piezoelectric transducer built into the ultrasonic dispersion syringe to disperse the conductive particles in the photosensitive solution in real time using ultrasound. Simultaneously, turn on the syringe pump to inject the photosensitive solution stored in the ultrasonic dispersion syringe into the acoustic holographic chip until the photosensitive solution contacts the pre-cured film. Then, turn on the curing lamp to cure the photosensitive solution through localized illumination and connect it to the pre-cured film. The curing lamp is subsequently kept on. Step 4: Adjust the injection rate of the syringe pump and the rotation speed of the take-up roller to maintain a uniform injection speed of the photosensitive solution, while using the take-up roller to pull out the cured conductive film. During this process, it is necessary to ensure that the injection rate of the photosensitive solution and the pull-out rate of the conductive film are balanced; Step 5: Turn on the acoustic wave excitation device, observe the arrangement of the conductive particles through a stereo microscope, and observe whether the pattern formed by the conductive particles is continuous. At the same time, fine-tune the injection rate of the injection pump and the rotation speed of the winding roller, change the injection rate of the photosensitive solution and the pulling-out rate of the conductive film until the pattern formed by the conductive particles is continuous. Continue to inject the photosensitive solution and rotate the winding roller at a uniform speed, and continue to pull out the solidified conductive film to achieve continuous forming of the conductive film.

[0015] Optionally, in step 2, the pre-cured film is made of the same base material as the conductive film, but does not contain conductive particles.

[0016] The conductive film preparation device and method based on acoustic holographic microfluidics provided in this application have at least the following beneficial effects: 1. Taking into full consideration the influence of the electric field generated by the piezoelectric effect in the delay line region of traditional piezoelectric devices on the particle arrangement, the conductive particles are arranged using acoustic holography technology. This can more evenly and stably modulate the striped acoustic field in the microcavity, achieving the arrangement of conductive particles with arbitrary aspect ratios. 2. Combining microfluidics and holographic acoustic field modulation technology, the photosensitive solution is continuously injected, the particles are arranged, and the film is continuously solidified and pulled out to achieve continuous molding of the conductive film, which can meet the requirements of flexible conductive film size in different application scenarios; 3. The lead zirconate titanate piezoelectric transducer in the acoustic holographic sound field modulation module is reversibly connected to the acoustic holographic chip through a coupling fluid. The lead zirconate titanate piezoelectric transducer is reusable, the acoustic holographic chip is easy to replace, and different arrangements can be easily achieved. The acoustic holographic chip is formed by an injection molding process, which has the advantages of high flexibility, replaceability, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] in: Figure 1 1 is a schematic diagram of the overall structure of a conductive film preparation device based on acoustic holographic microfluidics according to an embodiment of the present application; Figure 2 1 is a schematic structural diagram of an acoustic holographic sound field modulation module in an acoustic holographic microfluidics-based conductive film preparation device according to an embodiment of the present application; Figure 3 Schematic diagram of the microchannel layer structure of the acoustic holographic sound field modulation module in the conductive film preparation device based on acoustic holographic microfluidics shown in one embodiment of the present application; Figure 4 Schematic diagram of the connection layer structure of the acoustic holographic sound field modulation module in the conductive film preparation device based on acoustic holography microfluidics shown in one embodiment of the present application; Figure 5 Schematic diagram of the acoustic mask layer structure of the acoustic holographic sound field modulation module in the conductive film preparation device based on acoustic holography microfluidics according to one embodiment of the present application; Figure 6 1 is a schematic cross-sectional view of an acoustic mask structure of a connecting layer and an acoustic mask layer in a conductive film preparation device based on acoustic holography microfluidics according to an embodiment of the present application; Figure 7 1 is a schematic structural diagram of a film pulling module in a conductive film preparation device based on acoustic holography microfluidics according to an embodiment of the present application; Figure 8 This is a schematic diagram of a conductive film prepared by a conductive film preparation device based on acoustic holographic microfluidics shown in an embodiment of the present application.

[0019] Description of main component symbols: 1. Syringe pump; 2. Ultrasonic dispersion syringe; 3. Connecting tube; 4. Microchannel layer; 5. Connecting layer; 6. Acoustic mask layer; 7. Coupling liquid; 8. Acoustic wave excitation device; 9. Curing lamp; 10. Pre-cured film; 11. Winding roller; 12. Photosensitive solution injection port; 13. Photosensitive solution flow channel; 14. Photosensitive solution chamber; 15. Notch; 16. Protruding microstructure; 17. Grooved microstructure; 18. Positioning groove; 19. Cured polymer matrix; 20. Linear array of conductive particles. DETAILED DESCRIPTION

[0020] To facilitate understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many other forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0021] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0022] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0024] According to one aspect of the present application, an embodiment of the present application provides a conductive film preparation device based on acoustic holographic microfluidics, such as Figure 1-Figure 7 As shown, the conductive film preparation device includes an acoustic holographic sound field modulation module, an ultrasonic dispersion injection module, a film pulling out module, a connecting tube 3 and a curing lamp 9; the acoustic holographic sound field modulation module includes an acoustic holographic chip and an acoustic wave excitation device 8 arranged at the bottom of the acoustic holographic chip; the ultrasonic dispersion injection module includes an injection pump 1 and an ultrasonic dispersion syringe 2; the film pulling out module includes a winding roller 11 and a pre-cured film 10 connected to the winding roller 11 at one end. It should be noted here that the pre-cured film 10 is made of the same material as the base material of the conductive film to be prepared, but does not contain conductive particles. The acoustic holographic chip includes an acoustic mask layer 6, a connecting layer 5 and a microchannel layer 4 arranged in sequence from bottom to top; the acoustic mask layer 6 is provided with a groove microstructure 17 with an isosceles trapezoidal cross section for modulating the striped standing wave sound field; the connecting layer 5 is provided with a convex microstructure 16 complementary to the groove microstructure 17 for the conduction of sound waves and interlayer bonding; a photosensitive solution flow channel 13 and a photosensitive solution chamber 14 are provided between the microchannel layer 4 and the connecting layer 5, the convex microstructure 16 is horizontally located within the boundary of the photosensitive solution chamber 14, and the microchannel layer 4 is provided with a convex microstructure 16 away from the light and away from the photosensitive solution flow channel 13. One end of the photosensitive solution chamber 14 is connected to the photosensitive solution injection port 12, and the ultrasonic dispersion syringe 2 is connected to the photosensitive solution injection port 12 through a connecting tube 3. The ultrasonic dispersion syringe 2 is used to inject a photosensitive solution mixed with conductive particles into the photosensitive solution injection port 12. The microchannel layer 4 is also provided with a notch 15 connected to one end of the photosensitive solution chamber 14 away from the photosensitive solution flow channel 13. The notch 15 is used for inserting the end of the pre-cured film 10 away from the winding roller 11 into the photosensitive solution chamber 14, and the curing lamp 9 is used to cure the photosensitive solution in contact with the pre-cured film 10.

[0025] The basic method of using the conductive film preparation device is as follows: 1) Prepare a photosensitive solution containing uniformly dispersed conductive particles, and store the photosensitive solution in an ultrasonic dispersion syringe 2; 2) Prepare a pre-cured film 10, insert one end of the prepared pre-cured film 10 into the photosensitive solution chamber 14 through the gap 15 of the microchannel layer 4, and connect the other end to the winding roller 11; 3) Use the ultrasonic dispersion syringe 2 to disperse the conductive particles in the photosensitive solution in real time, inject the photosensitive solution into the acoustic holographic chip through the injection pump 1, and cure the photosensitive solution through local illumination of the curing lamp 9 and connect it to the pre-cured film 10; 4) Turn on the acoustic wave excitation device 8 to arrange the conductive particles, continuously inject the photosensitive solution and rotate the winding roller 11 at a uniform speed, continuously extract the cured conductive film, and realize continuous molding of the conductive film.

[0026] This application fully considers the influence of the electric field generated by the piezoelectric effect in the delay line region of traditional piezoelectric devices on the arrangement of conductive particles, and adopts acoustic holography technology to arrange the conductive particles, which can more evenly and stably modulate the striped sound field in the microchamber and realize the arrangement of conductive particles with arbitrary aspect ratio.

[0027] The conductive particles in the photosensitive solution are patterned using acoustic holographic field modulation technology; the photosensitive solution is cured using a curing lamp 9 to form a conductive film; and the photosensitive solution containing conductive particles is continuously introduced, cured, and the conductive film is pulled out based on microfluidic technology to achieve continuous preparation of the conductive film.

[0028] It should be noted that acoustic holographic sound field modulation technology utilizes a specifically structured acoustic mask to modulate the plane longitudinal waves generated by the acoustic wave excitation device 8, forming acoustic pressure nodal lines with specific spacing in the photosensitive solution. The acoustic radiation force then concentrates and arranges the conductive particles along the nodal lines, forming conductive straight lines, wavy lines, and other complex continuous patterns. In the embodiment of this application, the conductive pattern corresponding to the acoustic mask structure is a linear array pattern.

[0029] In one embodiment, if Figure 1-Figure 3 As shown, the lower surface of the microchannel layer 4 is provided with a positioning groove 18 connected to the notch 15 and extending toward the raised microstructure 16. There is a spacing between the positioning groove 18 and the raised microstructure 16. The end of the pre-cured film 10 away from the winding roller 11 can be inserted into the positioning groove 18 through the notch 15. The positioning groove 18 plays a role in positioning the insertion depth of the pre-cured film 10. The curing lamp 9 is located above the acoustic holographic chip. The irradiation area of ​​the curing lamp 9 is strip-shaped, the long side of which is parallel to the width direction of the photosensitive solution chamber 14 and greater than the width of the photosensitive solution chamber 14, and the short side is greater than the spacing between the positioning groove 18 and the raised microstructure 16.

[0030] Specifically, the curing lamp 9 can locally cure the photosensitive solution at the contact point with the pre-cured film 10 through a slit of a specific size. The long side of the slit is parallel to the width direction of the photosensitive solution chamber 14 and is longer than the width of the photosensitive solution chamber 14. The short side width of the slit is about 200 μm.

[0031] In one embodiment, acoustic wave excitation device 8 is a lead zirconate titanate (PZT) piezoelectric transducer, which is connected to the bottom of acoustic mask layer 6 at a location corresponding to groove microstructure 17 via coupling fluid 7. Preferably, coupling fluid 7 is a water film with a thickness of 100 μm to 300 μm.

[0032] According to the above arrangement, the lead zirconate titanate piezoelectric transducer and the acoustic holographic chip are reversibly connected through the water film, the lead zirconate titanate piezoelectric transducer is reusable, the acoustic holographic chip is easy to replace, and different arrangement forms are easy to achieve.

[0033] In a specific embodiment, Figure 2 and Figure 6 As shown, in the groove microstructure 17 , the length a of the upper base of the isosceles trapezoid is 60 μm-100 μm, the length of the lower base b is 500 μm, and the height h is 170 μm-220 μm.

[0034] The diameter of the photosensitive solution injection port 12 is 2 mm, the width of the photosensitive solution flow channel 13 is 1 mm, and the height is 200 μm; the width of the photosensitive solution chamber 14 is 15 mm, and the height is 200 μm; the photosensitive solution flow channel 13 and the photosensitive solution chamber 14 are transitioned at an oblique angle, and the angle between the oblique angle and the channel is 30°-45°.

[0035] In one embodiment, both the microchannel layer 4 and the connecting layer 5 are made of polydimethylsiloxane (PDMS). The microchannel layer 4 is fabricated using soft lithography, while the connecting layer 5 is formed by casting PDMS onto the acoustic mask layer 6 using a mold. The thickness of the connecting layer 5 is 30-80 μm. The interface between the microchannel layer 4 and the connecting layer 5 is bonded at room temperature using oxygen plasma treatment. This arrangement allows the acoustic holographic chip to be formed using an injection molding process, offering the advantages of high flexibility, interchangeability, and low cost.

[0036] It should be noted that the parameters of the groove microstructure 17 are calculated by the iterative angular spectrum method; the calculation process includes the following steps: 1. drawing a binary amplitude diagram of the target stripe sound field; 2. calculating the angular spectrum of the target plane sound field; 3. back-propagating the angular spectrum to the surface of the sound mask and calculating the complex sound pressure distribution; 4. retaining the phase of the sound field on the surface of the sound mask and resetting the amplitude; 5. calculating the angular spectrum of the sound mask surface after reset and forward transmitting it to the target plane; 6. calculating the sound field distribution of the target plane after transmission, comparing the error with the design value, and iteratively calculating.

[0037] According to another aspect of the present application, an embodiment of the present application further provides a method for preparing a conductive film based on acoustic holographic microfluidics. Based on the conductive film preparation device in any of the above embodiments, the conductive film preparation method includes the following steps: Step 1: Prepare a photosensitive solution containing conductive particles and store the photosensitive solution in an ultrasonic dispersion syringe 2; specifically, mix the polymer matrix solution, photoinitiator, diluent and conductive particles in proportion, and then ultrasonically vibrate for 10 minutes to prepare a photosensitive solution, store the photosensitive solution in an ultrasonic dispersion syringe 2, and then use a connecting tube 3 to connect the outlet of the ultrasonic dispersion syringe 2 to the photosensitive solution injection port 12 of the acoustic holographic chip.

[0038] Step 2: Prepare a pre-cured film 10. Attach one end of the prepared pre-cured film 10 to the take-up roller 11, and insert the other end into the photosensitive solution chamber 14 through the notch 15. Specifically, mix the polymer matrix solution, photoinitiator, and diluent in the same proportion as in step 1, and then ultrasonically vibrate for 10 minutes to prepare a pre-cured film 10 solution. Attach two strips of film with the same thickness as the conductive film to be prepared between two glass plates, forming a four-sided closed chamber with the two glass plates. Use a pipette to inject the pre-cured film 10 solution into the chamber. After curing with a curing lamp 9, cut it to a suitable size to ensure that it can fit into the notch 15 on the acoustic holographic chip. Attach one end of the pre-cured film 10 to the take-up roller 11 with strong glue or strong tape, and insert the other end into the photosensitive solution chamber 14 through the notch 15 until it reaches the positioning groove 18.

[0039] Step 3: Turn on the piezoelectric transducer built into the ultrasonic dispersion syringe 2, and use ultrasonic waves to disperse the conductive particles in the photosensitive solution in real time. At the same time, turn on the injection pump 1 to inject the photosensitive solution stored in the ultrasonic dispersion syringe 2 into the acoustic holographic chip until the photosensitive solution contacts the pre-cured film 10. Then, turn on the curing lamp 9 to cure the photosensitive solution through local illumination and connect it to the pre-cured film 10. The curing lamp 9 is kept on all the time.

[0040] Step 4: Adjust the injection rate of syringe pump 1 and the speed of take-up roller 11 to maintain a constant injection rate of the photosensitive solution. Simultaneously, use take-up roller 11 to pull out the cured conductive film. During this process, the injection rate of the photosensitive solution and the pull-out rate of the conductive film must be balanced. Therefore, the polymer matrix of the conductive film should be selected from a material with a high elastic modulus and strong tensile strength after curing.

[0041] Step 5: Turn on the acoustic wave excitation device 8, observe the arrangement of the conductive particles through a stereo microscope, and observe whether the pattern formed by the conductive particles is continuous. At the same time, fine-tune the injection rate of the injection pump 1 and the rotation speed of the winding roller 11, change the injection rate of the photosensitive solution and the pulling-out rate of the conductive film, until the pattern formed by the conductive particles is continuous, continue to inject the photosensitive solution and rotate the winding roller 11 at a uniform speed, and continue to pull out the solidified conductive film to achieve continuous forming of the conductive film.

[0042] The conductive film preparation method utilizes acoustic holographic field modulation technology to pattern the conductive particles in the photosensitive solution; utilizes a curing lamp 9 to cure the photosensitive solution to form a conductive film; and based on microfluidic technology, the photosensitive solution containing the conductive particles is continuously introduced, cured, and the conductive film is pulled out to achieve continuous preparation of the conductive film.

[0043] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0044] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A conductive film preparation device based on acoustic holographic microfluidics, characterized in that: It includes an acoustic holographic sound field modulation module, an ultrasonic dispersion injection module, a film pulling module, a connecting pipe and a curing lamp; the acoustic holographic sound field modulation module includes an acoustic holographic chip and a sound wave excitation device arranged at the bottom of the acoustic holographic chip; the ultrasonic dispersion injection module includes an injection pump and an ultrasonic dispersion syringe; the film pulling module includes a winding roller and a pre-cured film connected to the winding roller at one end; The acoustic holographic chip comprises an acoustic mask layer, a connection layer and a microchannel layer arranged in sequence from bottom to top; the acoustic mask layer is provided with a groove microstructure with an isosceles trapezoidal cross section for modulating a stripe-shaped standing wave acoustic field; the connection layer is provided with a convex microstructure complementary to the groove microstructure for conducting acoustic waves and interlayer bonding; A photosensitive solution flow channel and a photosensitive solution chamber that are interconnected are provided between the microchannel layer and the connecting layer. The horizontal position of the raised microstructure is located within the boundary of the photosensitive solution chamber. A photosensitive solution injection port that is connected to an end of the photosensitive solution flow channel away from the photosensitive solution chamber is provided on the microchannel layer. The ultrasonic dispersion syringe is connected to the photosensitive solution injection port through the connecting pipe. The ultrasonic dispersion syringe is used to inject a photosensitive solution mixed with conductive particles into the photosensitive solution injection port. A notch that is connected to an end of the photosensitive solution chamber away from the photosensitive solution flow channel is also provided on the microchannel layer. The notch is used for inserting an end of the precured film away from the winding roller into the photosensitive solution chamber. The curing lamp is used to cure the photosensitive solution at a portion in contact with the precured film.

2. The conductive film preparation device according to claim 1, characterized in that: The lower surface of the microchannel layer is provided with a positioning groove connected to the notch and extending to the protruding microstructure, and a spacing is provided between the positioning groove and the protruding microstructure. The end of the pre-cured film away from the winding roller can be inserted into the positioning groove through the notch. The curing lamp is located above the acoustic holographic chip. The irradiation area of ​​the curing lamp is a strip, the long side of which is parallel to the width direction of the photosensitive solution chamber and is larger than the width of the photosensitive solution chamber, and the short side is larger than the spacing between the positioning groove and the protruding microstructure.

3. The conductive film preparation device according to claim 1, characterized in that: The acoustic wave excitation device is a lead zirconate titanate piezoelectric transducer, and the lead zirconate titanate piezoelectric transducer is connected to the bottom of the acoustic mask layer at a position corresponding to the groove microstructure through a coupling liquid.

4. The conductive film preparation device according to claim 1, characterized in that: In the groove microstructure, the upper base length of the isosceles trapezoid is 60 μm-100 μm, the lower base length is 500 μm, and the height is 170 μm-220 μm.

5. The conductive film preparation device according to claim 1, characterized in that: The diameter of the photosensitive solution injection port is 2mm, the width of the photosensitive solution flow channel is 1mm, and the height is 200μm; the width of the photosensitive solution chamber is 15mm, and the height is 200μm; the photosensitive solution flow channel and the photosensitive solution chamber are transitioned through an oblique angle, and the angle between the oblique angle and the channel is 30°-45°.

6. The conductive film preparation device according to claim 1, characterized in that: The microchannel layer and the connecting layer are both made of polydimethylsiloxane. The microchannel layer is prepared by soft lithography, and the connecting layer is prepared by pouring polydimethylsiloxane on the acoustic mask layer through a mold; the contact surface between the microchannel layer and the connecting layer is bonded at room temperature by oxygen plasma treatment.

7. The conductive film preparation device according to claim 6, characterized in that: The thickness of the connecting layer is 30 μm-80 μm.

8. The conductive film preparation device according to claim 1, characterized in that: The parameters of the groove microstructure are calculated by an iterative angular spectrum method; the calculation process includes the following steps:

1. drawing a binary amplitude diagram of the target stripe sound field; 2. calculating the angular spectrum of the target plane sound field; 3. back-propagating the angular spectrum to the surface of the sound mask and calculating the complex sound pressure distribution; 4. retaining the phase of the sound field on the surface of the sound mask and resetting the amplitude; 5. calculating the angular spectrum of the sound mask surface after reset and forward transmitting it to the target plane; 6. calculating the sound field distribution of the target plane after transmission, comparing the error with the design value, and iteratively calculating.

9. A method for preparing a conductive film based on acoustic holographic microfluidics, based on the conductive film preparation device according to any one of claims 1 to 8, characterized in that: The conductive film preparation method comprises the following steps: Step 1: preparing a photosensitive solution containing conductive particles, and storing the photosensitive solution in the ultrasonic dispersion syringe; Step 2: preparing a precured film, adhering one end of the prepared precured film to the winding roller, and inserting the other end into the photosensitive solution chamber through the notch; Step 3: Turn on the built-in piezoelectric transducer in the ultrasonic dispersion syringe, use ultrasonic waves to disperse the conductive particles in the photosensitive solution in real time, and turn on the injection pump at the same time to inject the photosensitive solution stored in the ultrasonic dispersion syringe into the acoustic holographic chip until the photosensitive solution contacts the pre-cured film, turn on the curing lamp, cure the photosensitive solution by local illumination and connect it to the pre-cured film, and keep the curing lamp turned on afterwards; Step 4: adjusting the injection rate of the injection pump and the rotation speed of the take-up roller to maintain a uniform injection speed of the photosensitive solution, and at the same time using the take-up roller to pull out the solidified conductive film. In this process, it is necessary to ensure that the injection rate of the photosensitive solution and the pull-out rate of the conductive film are balanced; Step 5: Turn on the acoustic wave excitation device, observe the arrangement of the conductive particles through a stereo microscope, observe whether the pattern formed by the conductive particles is continuous, and at the same time fine-tune the injection rate of the injection pump and the rotation speed of the winding roller, change the injection rate of the photosensitive solution and the conductive film pulling-out rate until the pattern formed by the conductive particles is continuous, continue to inject the photosensitive solution and rotate the winding roller at a uniform speed, and continue to pull out the solidified conductive film to achieve continuous molding of the conductive film.

10. The method for preparing a conductive film according to claim 9, characterized in that: In step 2, the pre-cured film is made of the same base material as the conductive film, but does not contain conductive particles.

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