Bionic flexible multimode sensor and preparation method and application thereof

Abstract

The invention belongs to the technical field of flexible electronics and sensors, and particularly relates to a bionic flexible multimode sensor and a preparation method and application thereof, the sensor structure comprises magnetic bionic cilia, a polyimide film, a graphene mechanical receptor, a packaging layer and a wire; the magnetic bionic cilia array is arranged on the polyimide film; the graphene mechanical receptor is located in the area where the magnetic bionic cilia is located. When external fluid or an object touches the magnetic bionic cilia, the magnetic bionic cilia are bent, and the graphene mechanical receptor deforms along with the magnetic bionic cilia, so that the resistance is changed; resistance changes are converted into voltage signals to be output, and the flow velocity and the magnitude and direction of external force can be known through calibration. When an external magnetic field acts on the sensor, magnetic moment can be generated on the magnetic bionic cilia, the magnetic bionic cilia are driven to deflect, deformation and resistance change of the root graphene mechanical receptor are caused, and the intensity and direction of the external magnetic field can be inverted by detecting an electric signal.

Description

Technical Field

[0001] This invention belongs to the field of flexible electronics and sensor technology, specifically relating to a biomimetic flexible multimode sensor, its fabrication method, and its application. Background Technology

[0002] In recent years, with the rapid development of artificial intelligence, the Internet of Things, and soft robotics, the demand for multimodal sensors capable of simultaneously sensing multiple environmental information has become increasingly urgent. Multimodal sensors integrate multiple sensing functions into a single device, enabling the coordinated measurement and information fusion of various physical quantities such as force, heat, magnetism, and chemistry. This greatly enhances the environmental adaptability and information richness of sensing systems, demonstrating broad application prospects in cutting-edge fields such as intelligent robots, wearable medical devices, and virtual reality interaction.

[0003] Laser-induced graphene (LAQ) utilizes laser direct writing technology to pattern porous graphene structures on the surface of specific precursor materials in a single step, offering advantages such as high conductivity, flexibility, and simple processing. Adjusting laser parameters, process parameters, and doping modifications can influence the surface morphology, chemical, electrical, and mechanical properties of graphene, resulting in graphene with different properties, structures, and compositions. The simple process of LQ provides a new approach for fabricating high-performance flexible electrodes and sensor sensitive elements. Biomimetic flexible sensors, as an important branch of flexible sensors, have become a research hotspot in the fields of microtactile sensing, fluid dynamics measurement, and soft robotics. For example, arthropods use their antennae or cilia to capture weak disturbances in sound waves and airflow, enabling communication, obstacle avoidance, and foraging; migratory birds utilize their magnetically responsive cilia to sense the direction of the Earth's magnetic field, achieving precise positioning and migration across continents. Biomimetic technology has a significant impact on the design and fabrication of sensors.

[0004] Existing biomimetic flexible sensors are mostly based on a single sensing mode, only able to detect environmental stimuli through direct contact with force or strain. Multimodal sensors are primarily implemented through heterogeneous material integration and discrete sensor combinations. Heterogeneous material integration strategies face challenges such as low interfacial bonding strength between different functional materials and mismatched mechanical properties, making them prone to delamination or failure during application. Discrete sensor combinations, on the other hand, result in complex system structures, low integration density, significant signal interference, and difficulties in miniaturization. Current technologies struggle to achieve effective integration of high-sensitivity mechanical sensing and non-contact magnetic sensing while maintaining device flexibility, an integrated structure, and simplified manufacturing processes.

[0005] Therefore, developing a flexible biomimetic multimodal sensor based on novel materials and innovative processes to achieve a high degree of integration of force-magnetic and other multimodal sensing functions at the material, structural, and mechanism levels is of great scientific significance and application value for the development of intelligent sensing systems. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a biomimetic flexible multimode sensor, its fabrication method, and its applications.

[0007] This invention provides a biomimetic flexible multimode sensor, fabricated using the above-described method. The structure includes magnetic biomimetic cilia, a polyimide film, a graphene mechanoreceptor, an encapsulation layer, and wires. The magnetic biomimetic cilia array is disposed on the polyimide film. The graphene mechanoreceptor is disposed on the polyimide film, which includes one first graphene mechanoreceptor and two second graphene mechanoreceptors. The first graphene mechanoreceptor is located in the region where the magnetic biomimetic cilia are located, and the two second graphene mechanoreceptors are respectively disposed on opposite sides of the first graphene mechanoreceptor. Wires are connected to both ends of the first and second graphene mechanoreceptors. The encapsulation layer covers the polyimide film and the graphene mechanoreceptors.

[0008] Furthermore, the material of the magnetic biomimetic cilia is a mixture of magnetic particles and polyimide that has undergone magnetization treatment. The magnetic particles are neodymium iron boron (NdFeB) and strontium ferrite (SrFe). 12 O 19 The magnetic biomimetic cilia are composed of one or more of the following in any proportion: iron(II) oxide (Fe3O4) or iron(III) oxide (Fe2O4); the diameter of the magnetic biomimetic cilia is 320-1050 μm, the height is 5-10 mm, and the spacing between the cilia is 600-900 μm; the size (specification) of the magnetic biomimetic cilia array is a rectangular array of 4-6 columns, with 20-30 cilia per column; the size (specification) of the first graphene mechanoreceptor is 20-60 mm in length, 4-12 mm in width, and 5-50 nm in height; the size (specification) of the second graphene mechanoreceptor is 20-60 mm in length, 4-12 mm in width, and 5-50 nm in height; the spacing between the first and second graphene mechanoreceptors is 0.2-0.4 mm.

[0009] Another aspect of the present invention provides a method for fabricating the above-mentioned biomimetic flexible multimode sensor, comprising the following steps:

[0010] (1) Preparation of polyimide film and magnetic biomimetic cilia array

[0011] (1.1) Mix the magnetic particles with the polyamic acid solution, the precursor of polyimide, in a certain proportion. After stirring at a constant temperature until uniform, defoam the mixture. Inject the defoamed mixture into a mold with a pre-set fibrous structure. After injection, place the mold in a constant temperature drying oven for step-heat imidization treatment.

[0012] (1.2) After the mold cools to room temperature, take out the solidified unmagnetized fibers and polyimide film assembly. The unmagnetized fibers are arranged in a vertical array on the surface of the polyimide film. Place the solidified assembly in a steady magnetic field for magnetization treatment to obtain a magnetic biomimetic fiber and polyimide film assembly with a permanent magnetic moment.

[0013] (2) Laser-induced graphene preparation of mechanoreceptors

[0014] The magnetized biomimetic cilia and polyimide film assembly are fixed on a planar substrate; a porous three-dimensional graphene structure with a thickness of 5-50 nm is generated on the polyimide film by laser induction; and three uniformly distributed graphene mechanoreceptors with high conductivity are formed.

[0015] (3) Packaging of flexible bionic hair sensor

[0016] (3.1) Use conductive silver paste to fix six wires to three laser-induced graphene mechanoreceptors respectively, trim the excess polyimide film, and keep the length of 25-70mm and the width of 20-40mm.

[0017] (3.2) Prepare a flexible dimethylsiloxane material; cover the sensor surface with the flexible dimethylsiloxane material for encapsulation; then place it in a vacuum drying oven for curing treatment to complete the encapsulation of the sensor.

[0018] Preferably, the mass ratio of magnetic particles to polyamic acid solution in step (1.1) is 1:10.

[0019] Preferably, the magnetic particles are neodymium iron boron (NdFeB) or strontium ferrite (SrFe). 12 O 19 One or more of the following, iron(II) oxide or iron(III) oxide (Fe3O4), are mixed in any proportion, with a particle size of 0.5-10 μm.

[0020] Preferably, the defoaming treatment in step (1.1) is as follows: the mixed solution is placed in a vacuum dryer for defoaming treatment, with a vacuum degree of 250-350 Pa and a vacuuming time of 30-45 min.

[0021] Preferably, the mold described in step (1.1) has a thin film chamber and an array of micron-sized holes inside. The micron-sized holes are connected to the thin film chamber. The thin film chamber is 75-80 mm long, 20-40 mm wide, and 0.2-4 mm deep. The micron-sized holes have a diameter of 320-1050 μm, a depth of 5-10 mm, a hole spacing of 600-900 μm, and are arranged in 4-6 rectangular arrays with 20-30 cilia per column. The mold is made of stainless steel, and the inner surface of the micron-sized holes is hydrophobic.

[0022] Preferably, the step-heating imidization process in step (1.1) is as follows: heating at 80℃ for 30-50 min, heating at 120℃ for 30-50 min, heating at 180℃ for 30-50 min, heating at 200℃ for 20-30 min, heating at 220℃ for 20-30 min, and heating at 250℃ for 30-50 min, using a step-heating method to dry and solidify the mixed solution.

[0023] Preferably, the magnetic field strength of the steady-state magnetic field in step (1.2) is 0.5 T, and the magnetization time is 10-30 min.

[0024] As a preferred option, in step (2), a carbon dioxide infrared laser is used to perform laser direct writing on the surface of the polyimide film around the magnetic biomimetic cilia. The parameters of the laser-induced graphene are: cutting power of 9-11W and cutting speed of 40-50mm / s.

[0025] As a preferred embodiment, the preparation method of the dimethylsiloxane flexible material in step (3.1) is as follows: the dimethylsiloxane precursor and the curing agent are prepared in a mass ratio of 10:1 and stirred evenly to obtain the dimethylsiloxane flexible material.

[0026] Preferably, in step (3.2), the encapsulation thickness is 100-500 μm, the curing temperature is 50-60℃, and the curing time is 60-70 min.

[0027] In another aspect, the present invention provides an application of the above-mentioned biomimetic flexible multimodal sensor, which is applied to force-magnetic multimodal sensing to realize feedback of flow velocity, flow direction, pressure, and magnetic field environmental stimulation signals.

[0028] The working principle of the biomimetic flexible multimode sensor prepared in this invention is as follows:

[0029] When an external fluid flows or an object touches the magnetic biomimetic cilia, the cilia bend. The first graphene mechanoreceptor at the root of the cilia undergoes stretching and compression deformation, with its resistance changing differently depending on the bending angle. Simultaneously, two symmetrically distributed second graphene mechanoreceptors are subjected to stretching or compression deformation, one stretching and the other compressing. Connecting the graphene mechanoreceptor electrodes to a Wheatstone bridge circuit converts the resistance change into a highly sensitive voltage signal output. By calibrating the first graphene mechanoreceptor's electrical signal, the magnitude of the external force and flow velocity can be determined. The sign of the second graphene mechanoreceptor's electrical signal indicates the direction of the external force and the direction of fluid flow. When an external magnetic field acts on the sensor, it generates a magnetic torque on the magnetized magnetic biomimetic cilia, causing them to deflect. This deflection also causes deformation and resistance changes in the root graphene mechanoreceptor. By detecting the electrical signal, the strength and direction of the external magnetic field can be inferred. After the external load is removed, the magnetic biomimetic cilia return to their original state. The ciliary kinematic effects caused by force and magnetic fields are similar, but the signal characteristics may differ at different frequencies or amplitudes.

[0030] The beneficial effects of this invention are:

[0031] This invention integrates a magnetic functional unit and a graphene strain sensing unit onto a single biomimetic ciliary, achieving simultaneous detection of force and magnetic field signals. Both the ciliary substrate and the sensitive electrode share polyimide as their common material, and the "substrate-electrode" integration is achieved through laser-induced technology, resulting in a strong interface bond, eliminating the risk of interlayer delamination, and exhibiting excellent flexibility and mechanical durability. The magnetic ciliary is fabricated using a mature polyamic acid imidization process, ensuring good stability. The graphene mechanoreceptor is fabricated using laser direct writing technology, eliminating the need for masking, photolithography, or transfer steps, simplifying the process, reducing costs, and facilitating patterning, miniaturization, and mass production. The porous three-dimensional structure of the graphene mechanoreceptor is extremely sensitive to minute deformations, ensuring high sensor sensitivity. The magnetized ciliary possesses a defined magnetic moment, exhibiting sensitive response to magnetic fields. This sensor is soft, lightweight, and miniaturizable, making it highly suitable for applications such as tactile skin for soft robots, flow field and geomagnetic navigation in micro underwater vehicles, interactive input in wearable devices, and microenvironment detection in biomedicine. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the fabrication method of the biomimetic flexible multimode sensor of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the biomimetic flexible multimode sensor of the present invention;

[0034] Figure 3This is a three-dimensional structural diagram of the biomimetic flexible multimode sensor of the present invention;

[0035] Figure 4 This is a scanning electron microscope image of the mechanoreceptor of the biomimetic flexible multimode sensor of the present invention;

[0036] 1. Magnetic biomimetic cilia 2. Polyimide film 3. Graphene mechanoreceptor 4. Encapsulation layer 5. Wire Detailed Implementation

[0037] See Figure 1-4 As shown, the biomimetic flexible multimode sensor provided in this embodiment is prepared by the following method:

[0038] (1) Preparation of polyimide (PI) film and magnetic biomimetic cilia array

[0039] (1.1) 0.2 g of magnetic particles neodymium iron boron (NdFeB) and 2 g of polyimide precursor polyamic acid (PAA) solution were placed in a constant temperature magnetic stirrer and stirred for 50 min at a temperature range of 20-26℃. After stirring evenly, the mixture was placed in a vacuum dryer for defoaming treatment. The vacuum degree was 250-350 Pa and the vacuuming time was 30-45 min. The vacuuming method was slow vacuuming. The defoamed mixture was injected into a mold with a pre-set fibrous structure. The mold was provided with a thin film chamber and an array of micron-sized pores. The micron-sized pores were connected to the thin film chamber. The diameter of the micron-sized pores was 300-1000 μm, the depth was 5-10 mm, and the pore spacing was 600-2000 μm. The mold was made of stainless steel and the inner surface of the micron-sized pores was hydrophobically treated. After injection, the mold is placed in a constant temperature drying oven for step-heat imidization treatment. The process is as follows: heating at 80℃ for 30-50 min, heating at 120℃ for 30-50 min, heating at 180℃ for 30-50 min, heating at 200℃ for 20-30 min, heating at 220℃ for 20-30 min, and heating at 250℃ for 30-50 min. The mixed solution is dried and cured using a step-heating method.

[0040] (1.2) After the mold cools to room temperature, take out the solidified unmagnetized fibers and polyimide film assembly. The film is 75mm long, 20mm wide, and 0.2mm thick. The size (specification) of the biomimetic fiber array is a rectangular array of 4 columns, with 30 fibers in each column. The diameter of the fibers is 300μm, the height is 5mm, and the fiber spacing is 600μm. The unmagnetized fibers are arranged vertically on the surface of the polyimide film. The solidified assembly is placed in a steady magnetic field for magnetization. The magnetic field strength of the steady magnetic field is 0.5T, and the magnetization time is 10-30min. The magnetic particles inside the fibers are fully magnetized to obtain a magnetic biomimetic fiber 1 and polyimide film 2 assembly with permanent magnetic moment.

[0041] (2) Laser-induced graphene preparation of mechanoreceptors

[0042] The magnetized magnetic biomimetic cilia 1 and polyimide film 2 assembly are fixed on a planar substrate. A carbon dioxide infrared laser is used to perform laser direct writing on the surface of the polyimide film 2 around the magnetic biomimetic cilia 1. The parameters of the laser-induced graphene are: cutting power of 9-11W and cutting speed of 40-50mm / s. Under the thermal effect of the laser, a porous three-dimensional graphene structure is induced to form, with a graphene thickness of 5-50nm, forming a highly conductive laser-induced graphene mechanoreceptor 3 (the magnetic biomimetic cilia region forms the first graphene mechanoreceptor, and the two sides opposite the first graphene mechanoreceptor form the second graphene mechanoreceptor).

[0043] (3) Packaging of flexible bionic hair sensor

[0044] (3.1) Use conductive silver paste to fix and connect the six wires 5 to the three laser-induced graphene mechanoreceptors 3 respectively. Use scissors to trim the excess polyimide film 2. After trimming, the polyimide film is 35-40mm long and 15-20mm wide.

[0045] (3.2) The dimethylsiloxane precursor and curing agent are prepared at a mass ratio of 10:1 and stirred at room temperature using a magnetic stirrer for 10-20 min to obtain a dimethylsiloxane flexible material. The uniformly mixed dimethylsiloxane flexible material is then covered on the surface of the sensor for encapsulation, with the encapsulation layer 4 having a thickness of 100-500 μm. The sensor is then placed in a vacuum drying oven for curing at a curing temperature of 60℃ for 60-70 min to complete the encapsulation of the sensor.

[0046] The flexible multimodal sensor prepared in this embodiment can be applied to force-magnetic multimodal sensing. When external fluid flows or an object touches and applies force to the magnetic biomimetic cilia 1, the cilia 1 bends. The graphene mechanoreceptor 3 located at the root of the magnetic biomimetic cilia 1 undergoes stretching and compression deformation, and its resistance changes differently depending on the bending angle of the magnetic biomimetic cilia 1. By connecting the electrodes of the graphene mechanoreceptor 3 to a Wheatstone bridge circuit, the resistance change can be converted into a highly sensitive voltage signal output. Through calibration, the magnitude and direction of the flow velocity and the magnitude and direction of the external force can be determined. When an external magnetic field acts on the sensor, it generates a magnetic torque on the magnetized magnetic biomimetic cilia 1, causing the cilia 1 to deflect. This deflection also causes deformation and resistance change of the graphene mechanoreceptor 3 at the root. By detecting the electrical signal, the strength and direction of the external magnetic field can be inverted. After the external load is removed, the magnetic biomimetic cilia return to their original state. This achieves feedback of flow velocity, flow direction, pressure, and magnetic field environmental stimulation signals.

Claims

1. A biomimetic flexible multimode sensor, characterized in that: The device includes magnetic biomimetic cilia, a polyimide film, graphene mechanoreceptors, an encapsulation layer, and wires. The magnetic biomimetic cilia array is disposed on the polyimide film. The graphene mechanoreceptors are disposed on the polyimide film, which includes one first graphene mechanoreceptor and two second graphene mechanoreceptors. The first graphene mechanoreceptor is located in the region where the magnetic biomimetic cilia are located, and the two second graphene mechanoreceptors are respectively disposed on opposite sides of the first graphene mechanoreceptor. Wires are connected to the two ends of the first and second graphene mechanoreceptors. The encapsulation layer covers the polyimide film and the graphene mechanoreceptors.

2. The biomimetic flexible multimode sensor according to claim 1, characterized in that: The magnetic biomimetic cilia are made of a mixture of magnetic particles and polyimide, which has been magnetized. The magnetic particles are neodymium iron boron (NdFeB) and strontium ferrite (SrFe). 12 O 19 The magnetic biomimetic cilia are composed of one or more of the following in any proportion: iron(II) oxide (Fe3O4) or iron(III) oxide (Fe2O4); the diameter of the magnetic biomimetic cilia is 300-1000 μm, the height is 5-10 mm, and the spacing between the cilia is 600-900 μm; the magnetic biomimetic cilia array is a rectangular array with 4-6 columns, and each column contains 20-30 cilia; the size of the first type of graphene mechanoreceptor is 20-60 mm in length, 4-12 mm in width, and 5-50 nm in height; the size of the second type of graphene mechanoreceptor is 20-60 mm in length, 4-12 mm in width, and 5-50 nm in height, and the spacing between the first and second graphene mechanoreceptors is 0.2-0.4 mm.

3. The method for fabricating a biomimetic flexible multimode sensor as described in claim 1 or 2, characterized in that: Includes the following steps: (1) Preparation of polyimide film and magnetic biomimetic cilia array (1.1) Mix the magnetic particles with the polyamic acid solution, the precursor of polyimide, in a certain proportion. After stirring at a constant temperature until uniform, defoam the mixture. Inject the defoamed mixture into a mold with a pre-set fibrous structure. After injection, place the mold in a constant temperature drying oven for step-heat imidization treatment. (1.2) After the mold cools to room temperature, take out the solidified unmagnetized fibers and polyimide film assembly. The unmagnetized fibers are arranged in a vertical array on the surface of the polyimide film. Place the solidified assembly in a steady magnetic field for magnetization treatment to obtain a magnetic biomimetic fiber and polyimide film assembly with a permanent magnetic moment. (2) Laser-induced graphene preparation of mechanoreceptors The magnetized biomimetic cilia and polyimide film assembly are fixed on a planar substrate; a porous three-dimensional graphene structure with a thickness of 5-50 nm is generated on the polyimide film by laser induction; and three uniformly distributed graphene mechanoreceptors with high conductivity are formed. (3) Packaging of flexible bionic hair sensor (3.1) Use conductive silver paste to fix and connect 6 wires to three laser-induced graphene mechanoreceptors respectively, and trim the excess polyimide film; retain the dimensions of 25-70mm in length and 20-40mm in width; (3.2) Prepare a flexible dimethylsiloxane material; cover the sensor surface with the flexible dimethylsiloxane material for encapsulation; then place it in a vacuum drying oven for curing treatment to complete the encapsulation of the sensor.

4. The preparation method according to claim 3, characterized in that: In step (1.1), the mass ratio of magnetic particles to polyamic acid solution is 1:10; the magnetic particles are neodymium iron boron (NdFeB) and strontium ferrite (SrFe). 12 O 19 One or more of the following are mixed in any proportion: iron(II) oxide or iron(III) oxide (Fe3O4), with a particle size of 0.5-10 μm.

5. The preparation method according to claim 3, characterized in that: The defoaming treatment in step (1.1) is as follows: the mixed solution is placed in a vacuum dryer for defoaming treatment, with a vacuum degree of 250-350 Pa and a vacuuming time of 30-45 min; the mold has a thin film chamber and an array of micron-sized pores inside, which are connected to the thin film chamber. The thin film chamber is 75-80 mm long, 20-40 mm wide, and 0.2-4 mm deep; the micron-sized pores have a diameter of 320-1050 μm, a depth of 5-10 mm, a pore spacing of 600-900 μm, and are arranged in a rectangular array of 4-6 columns, with 20-30 cilia per column. The mold is made of stainless steel, and the inner surface of the micron-sized pores is hydrophobically treated; the step-heat imidization process is as follows: heating at 80℃ for 30-50 min, heating at 120℃ for 30-50 min, heating at 180℃ for 30-50 min, and heating at 200℃ for 20-30 min. The mixed solution was dried and cured by heating at 220℃ for 20-30 minutes and at 250℃ for 30-50 minutes using a stepped heating method.

6. The preparation method according to claim 3, characterized in that: The magnetic field strength of the steady-state magnetic field in step (1.2) is 0.5 T, and the magnetization time is 10-30 min.

7. The preparation method according to claim 3, characterized in that: In step (2), a carbon dioxide infrared laser is used to perform laser direct writing on the surface of the polyimide film around the magnetic biomimetic fibers. The parameters of the laser-induced graphene are: cutting power of 9-11W and cutting speed of 40-50mm / s.

8. The preparation method according to claim 3, characterized in that: The preparation method of the dimethylsiloxane flexible material in step (3.1) is as follows: the dimethylsiloxane precursor and the curing agent are prepared in a mass ratio of 10:1 and stirred evenly to obtain the dimethylsiloxane flexible material.

9. The preparation method according to claim 3, characterized in that: In step (3.2), the encapsulation thickness is 100-500 μm, the curing temperature is 50-60℃, and the curing time is 60-70 min.

10. The application of the biomimetic flexible multimode sensor according to claim 1 or 2, or the biomimetic flexible multimode sensor prepared by any one of claims 3-9, characterized in that: It is applied to force-magnetic multimodal sensing to realize feedback of flow velocity, flow direction, pressure, and magnetic field environmental stimulation signals.

Images