A flexible pressure sensor imitating a neural synapse and a preparation method thereof
By designing a flexible pressure sensor that mimics neural synapses and employing multi-scale microstructures and three-dimensional porous graphene layers, the problem of sensitivity degradation under high pressure was solved, achieving high sensitivity and stable sensing performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INSTITUTE OF TECHNOLOGY (SHENZHEN) (INSTITUTE OF SCIENCE AND TECHNOLOGY INNOVATION HARBIN INSTITUTE OF TECHNOLOGY SHENZHEN)
- Filing Date
- 2023-09-28
- Publication Date
- 2026-06-12
AI Technical Summary
Existing flexible pressure sensors exhibit decreased sensitivity under high pressure, and the limited contact area of the sensitive layer leads to unstable sensing performance.
A flexible pressure sensor mimicking neural synapses was designed, employing a multi-scale microstructure in the upper and lower sensitive layers, including a hemispherical microstructure mimicking the axon terminal of a neuron and a cylindrical concave structure at the dendritic terminal, combined with a three-dimensional porous graphene layer to increase the contact area and maintain the conductive pathway under high pressure.
It significantly improves the sensitivity and stability of the sensor, ensuring that it can maintain high sensitivity detection performance under high pressure, and the manufacturing process is simple and low cost.
Smart Images
Figure CN117309203B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to flexible pressure sensors, and more specifically to a flexible pressure sensor that mimics a neural synapse and its fabrication method. Background Technology
[0002] With the rapid development of next-generation electronic information technology, flexible sensors have played a crucial role in various fields such as smart wearable electronic devices, medical rehabilitation equipment, human-computer interaction systems, and intelligent robots. By using flexible materials or special designs to achieve structural stretching and bending, flexible sensors possess excellent extensibility, flexibility, and the ability to be bent, folded, and worn. This gives them a flexible deformation capability that traditional rigid sensors cannot match, effectively compensating for the shortcomings of rigid sensors in achieving unstructured human-machine-environment perception and interaction. They can closely conform to the surface of complex three-dimensional structures, thus meeting the application requirements of real-time, ever-changing target motion patterns in complex environments.
[0003] Flexible pressure sensors, by sensing pressure, are essential for force / tactile perception, human-computer interaction, and physiological signal monitoring. Piezoresistive microstructures, as a type of sensing element, offer significant advantages such as simple structure, strong anti-interference capability, wide measurement range, and simple detection circuitry. However, current flexible pressure sensor microstructures are primarily single-scale, primarily hemispherical and pyramidal in shape. These structures suffer from limited contact area between the upper and lower sensitive layers, resulting in limited sensitivity. Furthermore, they are prone to deformation saturation under high pressure, leading to a sharp decrease in high-pressure detection sensitivity. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a flexible pressure sensor that mimics a neural synapse and its fabrication method, achieving high-sensitivity measurement and stable sensing performance under high pressure.
[0005] The technical solution adopted in this invention is as follows:
[0006] A flexible pressure sensor that mimics a neural synapse includes an upper flexible substrate, an upper electrode disposed on the lower surface of the upper flexible substrate, an upper sensitive layer disposed below the upper electrode, a lower sensitive layer disposed below the upper sensitive layer and interlocked with the upper sensitive layer, a lower electrode disposed below the lower sensitive layer, and a lower flexible substrate disposed below the lower electrode.
[0007] The upper sensitive layer consists of protruding microstructures mimicking the ends of neuron axons and a conductive layer, with the conductive layer covering the surface of the protruding microstructures.
[0008] The lower sensitive layer consists of a secondary rough microstructure and a recessed structure mimicking the dendritic ends of neurons, with the secondary rough microstructure disposed on the surface of the recessed structure.
[0009] Multiple of the aforementioned protruding microstructures form a protruding microstructure array;
[0010] Multiple recessed structures form a recessed structure array;
[0011] The recessed structure serves as the bottom support for the raised microstructure. After the upper and lower sensitive layers are brought close together, the raised microstructure is located in the cavity of the recessed structure.
[0012] The conductive layer is a three-dimensional porous graphene layer.
[0013] The protruding microstructure is a hemispherical microstructure that mimics the axon terminal of a neuron.
[0014] The recessed structure is a cylindrical recessed structure, and the cylindrical recessed structure has multiple concentric cavities inside. The multiple concentric cavities are arranged at equal intervals, and the height of the cavities increases sequentially from the inside to the outside.
[0015] The secondary rough microstructure is granular or lamellar.
[0016] The spacing between the hemispherical microstructure arrays is 2-4 times the radius of the hemispherical microstructure.
[0017] The upper and lower flexible substrates are made of polyethylene terephthalate (PET) or polyimide (PI) film.
[0018] The upper and lower electrodes are conductive thin layers made of gold, silver, or conductive silver paste.
[0019] The upper and lower sensitive layers are made of polydimethylsiloxane (PDMS) doped with multi-walled carbon nanotubes.
[0020] A method for fabricating a flexible pressure sensor that mimics a neural synapse includes the following steps:
[0021] 1) Use 3D printing or photolithography-etching methods to fabricate molds for the upper hemispherical microstructure array and the lower cylindrical boss array;
[0022] 2) Mix PDMS and curing agent in proportion, stir magnetically, and then add a certain mass fraction of multi-walled carbon nanotubes to the mixture and stir magnetically and disperse ultrasonically.
[0023] 3) The prepared multi-walled carbon nanotubes / PDMS are poured into the mold, placed in a drying oven for heating and curing, and then peeled off from the mold to obtain the hemispherical protrusion array of the upper sensitive layer and the cylindrical protrusion array of the lower sensitive layer.
[0024] 4) Using an ultraviolet laser, a three-dimensional porous graphene layer is generated on the surface of the hemispherical microstructure of the upper sensitive layer by laser induction.
[0025] 5) Using a CO2 laser, laser ablation is performed on the cylindrical protrusions of the lower sensitive layer to form a cylindrical recessed structure array and its secondary rough microstructure.
[0026] 6) Electrodes are formed by sputtering, vapor deposition, or printing conductive thin films on the surfaces of the upper and lower flexible substrates;
[0027] 7) Align and attach the lower flexible substrate with the lower electrode, the lower sensitive layer, the upper sensitive layer, and the upper flexible substrate with the upper electrode in sequence, and apply glue around the perimeter to encapsulate it into a flexible pressure sensor that mimics a neural synapse.
[0028] The beneficial effects of this invention are:
[0029] (1) By designing hemispherical microstructures mimicking the axon terminals of neurons and cylindrical concave structures mimicking the dendrite terminals of neurons in the upper and lower sensitive layers respectively, and by utilizing the semi-enclosed structure design of the upper and lower sensitive layers with protrusions and concavities mimicking synapses, the contact area of the sensitive structures in the upper and lower sensitive layers is significantly increased, greatly increasing the conductive pathway, thereby significantly improving the sensing sensitivity.
[0030] (2) The multi-scale sensitive microstructure mimicking neuron synapses allows the inner ring structure of the cylindrical concave structure of the lower sensitive layer to still have new contact points with the hemispherical microstructure of the upper sensitive layer after being compressed and deformed to saturation, thus ensuring the conductive path and guaranteeing the detection sensitivity of the sensor under high pressure.
[0031] (3) Three-dimensional porous graphene is fabricated on the surface of the hemispherical microstructure of the upper sensitive layer by laser induction using a nanosecond laser, and a cylindrical concave structure and its secondary rough surface are fabricated on the surface of the lower sensitive layer by laser ablation using a nanosecond laser. This method has the advantages of simple preparation process and low cost. Attached Figure Description
[0032] Figure 1 This is a cross-sectional view of the flexible pressure sensor of the present invention;
[0033] Figure 2 This is a cross-sectional view of the neural synapse-like structural unit of the present invention;
[0034] Figure 3 This is a schematic diagram of the sensitive layer of the present invention;
[0035] Figure 4 This is a schematic diagram of the lower sensitive layer of the present invention;
[0036] Figure 5 This is a schematic diagram illustrating the fabrication of the upper and lower sensitive layers of this invention;
[0037] In the figure: upper flexible substrate 100; upper electrode 200; upper sensitive layer 300; hemispherical microstructure 310; three-dimensional porous graphene layer 320; lower sensitive layer 400; secondary rough microstructure 410; cylindrical recessed structure 420; lower electrode 500; lower flexible substrate 600. Detailed Implementation
[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0039] like Figure 1 , Figure 2 As shown, the present invention mainly consists of an upper flexible substrate 100, an upper electrode 200, an upper sensitive layer 300, a lower sensitive layer 400, a lower electrode 500, and a lower flexible substrate 600.
[0040] like Figure 1 , Figure 2 As shown, the upper electrode 200 is disposed on the surface of the upper flexible substrate 100, and the lower electrode 500 is disposed on the surface of the lower flexible substrate 600. The upper electrode 200 and the lower electrode 500 are conductive thin films with a thickness of 50-100 μm.
[0041] like Figure 2 , Figure 3 As shown, the upper sensitive layer 300 is composed of a hemispherical microstructure 310 and a three-dimensional porous graphene layer 320. The surface of the hemispherical microstructure 310, which mimics the axon terminal of a neuron, is covered with a three-dimensional porous graphene layer 320.
[0042] like Figure 2 , Figure 3 As shown, the radius of the hemispherical microstructure 310 is 250-300 μm, the thickness of the three-dimensional porous graphene layer 320 is 10-20 μm, and the spacing of the hemispherical microstructure 310 array is 2-4 times the radius of the hemispherical microstructure 310.
[0043] like Figure 2 , Figure 4 As shown, the lower sensitive layer 400 is composed of a secondary rough microstructure 410 and a cylindrical concave structure 420. The secondary rough microstructure 410 is provided on the surface of the cylindrical concave structure 420 that mimics the dendritic end of a neuron. The secondary rough microstructure 410 is granular or lamellar, and the height of the lower sensitive layer 400 is 10-20 μm.
[0044] like Figure 2 , Figure 4As shown, the cylindrical recessed structure 420 is a cylinder with a radius of 50-60 μm and a height of 90-100 μm. The cylindrical recessed structure 420 contains multiple concentric cavities, with 2-5 cavities of uniform wall thickness (50-60 μm) arranged at equal intervals. The height of the cavities increases sequentially from the inside out. The spacing of the cylindrical recessed structure 420 array is the same as the spacing of the hemispherical microstructure 310 array.
[0045] like Figure 1 , Figure 2 As shown, the cylindrical recessed structure 420 serves as the bottom support. After the upper sensitive layer 300 and the lower sensitive layer 400 are aligned, the three-dimensional porous graphene multi-scale structure is stacked in the cavity of the cylindrical recessed structure. When there is no force, the three-dimensional porous graphene 320 is in contact with the upper cylindrical surface of the lower sensitive layer 400. When there is force, the secondary rough microstructure 410 on the surface of the three-dimensional porous graphene layer 320 and the cylindrical recessed structure 420 first undergo contact deformation, resulting in an increase in the contact area and a decrease in the contact resistance. When the pressure increases, the hemispherical microstructure 310 and the cylindrical recessed structure 420 deform as a whole, and the hemispherical microstructure 310 comes into contact with the concentric cavity in sequence, thereby reducing the contact resistance and increasing the conductive pathways inside the material, ensuring the detection sensitivity under high pressure.
[0046] The upper flexible substrate 100 and the lower flexible substrate 600 are made of PET or PI film. The advantages of PET and PI films, such as their flexibility and good toughness, effectively protect the internal structure of the sensor.
[0047] The upper electrode 200 and the lower electrode 500 are made of gold, silver or conductive silver paste.
[0048] The materials of the upper sensitive layer 300 and the lower sensitive layer 400 are both PDMS doped with 8% to 20% by mass of multi-walled carbon nanotubes. By utilizing the characteristic that the resistance of PDMS doped with multi-walled carbon nanotubes decreases when subjected to pressure, and the output signal changes, the detection sensitivity of the sensor under high pressure is ensured.
[0049] like Figure 5 As shown, the fabrication of the flexible pressure sensor mimicking a neural synapse provided in this invention includes the following steps:
[0050] 1) Use 3D printing or photolithography-etching to fabricate an upper sensitive layer 300 with a hemispherical microstructure 310 array and a lower sensitive layer 400 with a cylindrical boss array.
[0051] 2) Mix PDMS and curing agent in a certain proportion, stir magnetically, add a certain mass fraction of multi-walled carbon nanotubes to the mixture, stir magnetically, and then disperse ultrasonically.
[0052] 3) Pour the prepared multi-walled carbon nanotubes / PDMS into the mold, place it in a drying oven for heating and curing, and then peel it off from the mold;
[0053] 4) Using an ultraviolet laser, three-dimensional porous graphene 320 is generated on the surface of the hemispherical microstructure 310 of the upper sensitive layer 300 by laser induction.
[0054] 5) Using a CO2 laser, the cylindrical protrusions of the lower sensitive layer 400 are laser-ablated to form an array of cylindrical recessed structures 420 and its secondary rough microstructures 410 on the surface.
[0055] 6) Sputter, vapor deposit, or print conductive thin films on the surfaces of the upper flexible substrate 100 and the lower flexible substrate 600 to form the upper electrode 200 and the lower electrode 500.
[0056] 7) Align and attach the lower flexible substrate 600 with the lower electrode 500, the lower sensitive layer 400, the upper sensitive layer 300, and the upper flexible substrate 100 with the upper electrode 200 in sequence to form a flexible pressure sensor that mimics a nerve synapse.
[0057] Example:
[0058] In the flexible pressure sensor mimicking a neural synapse provided in this embodiment, the radius of the hemispherical microstructure 310 is 300 μm, the thickness of the three-dimensional porous graphene layer 320 is 10 μm, and the spacing of the hemispherical microstructure 310 array is 400 μm; the central cylinder of the cylindrical recessed structure 420 has a radius of 50 μm and a height of 90 μm, there are two multi-level concentric cavities, each with a wall thickness of 50 μm, the secondary rough microstructure 410 on the surface has a height of 10 μm and a layered morphology, and the spacing of the cylindrical recessed structure 420 array is 400 μm; the thickness of the electrode is 50 μm.
[0059] The specific fabrication process of the flexible pressure sensor mimicking a nerve synapse in this embodiment is as follows:
[0060] 1) Use 3D printing to fabricate an upper sensitive layer 300 with a hemispherical microstructure 310 array and a lower sensitive layer 400 with a cylindrical boss array;
[0061] 2) Mix PDMS and curing agent at a ratio of 10:1 and stir magnetically for 10 min; add 8% by mass of multi-walled carbon nanotubes to the mixture and stir magnetically for 10 min, then disperse ultrasonically for 10 min;
[0062] 3) Pour the prepared multi-walled carbon nanotubes / PDMS into the mold, place it in a drying oven at 100℃ for 30 minutes to solidify and then peel it off from the mold;
[0063] 4) Using an ultraviolet laser with a wavelength of 355nm and a power of 3W, and a scanning speed of 60mm / s, three-dimensional porous graphene was generated on the surface of the hemispherical microstructure 310 of the upper sensitive layer 300 by laser induction.
[0064] 5) Using a CO2 laser with a wavelength of 10600nm and a power of 6W, and a scanning speed of 360mm / s, laser ablation is performed on the cylindrical protrusion of the lower sensitive layer 400 to achieve integrated ablation forming of the cylindrical recessed structure 420 and the surface secondary rough microstructure 410.
[0065] 6) An electrode is formed by sputtering a 50 μm gold film on the surface of the PI film;
[0066] 7) Align and attach the lower flexible substrate 600 with the lower electrode 500, the lower sensitive layer 400, the upper sensitive layer 300, and the upper flexible substrate 100 with the upper electrode 200 in sequence, and apply glue around the perimeter to encapsulate it into a flexible pressure sensor that mimics a neural synapse.
Claims
1. A flexible pressure sensor mimicking a neural synapse, characterized in that, It includes an upper flexible substrate (100), an upper electrode (200) disposed on the lower surface of the upper flexible substrate (100), an upper sensitive layer (300) disposed on the lower side of the upper electrode (200), a lower sensitive layer (400) disposed below the upper sensitive layer (300) and interlocked with the upper sensitive layer (300), a lower electrode (500) disposed below the lower sensitive layer (400), and a lower flexible substrate (600) disposed below the lower electrode (500). The upper sensitive layer (300) is composed of a protruding microstructure (310) mimicking the axon terminal of a neuron and a conductive layer (320), wherein the conductive layer (320) covers the surface of the protruding microstructure (310); The lower sensitive layer (400) is composed of a secondary rough microstructure (410) and a recessed structure (420) mimicking the dendritic ends of neurons, with the secondary rough microstructure (410) disposed on the surface of the recessed structure (420). Multiple of the protruding microstructures (310) form a protruding microstructure array; Multiple recessed structures (420) form a recessed structure array; The recessed structure (420) serves as the bottom support of the raised microstructure (310). After the upper sensitive layer (300) and the lower sensitive layer (400) are close together, the raised microstructure (310) is located in the cavity of the recessed structure (420). The conductive layer (320) is a three-dimensional porous graphene layer; The protruding microstructure (310) is a hemispherical microstructure that mimics the terminal axon of a neuron; The recessed structure (420) is a cylindrical recessed structure. The cylindrical recessed structure has multiple concentric cavities inside. The multiple concentric cavities are arranged at equal intervals, and the cavity height increases sequentially from the inside to the outside. The upper sensitive layer (300) and the lower sensitive layer (400) are made of polydimethylsiloxane (PDMS) doped with multi-walled carbon nanotubes.
2. The flexible pressure sensor mimicking a neural synapse according to claim 1, characterized in that: The secondary rough microstructure (410) is granular or lamellar.
3. The flexible pressure sensor mimicking a neural synapse according to claim 2, characterized in that: The spacing between the array of raised microstructures (310) is 2-4 times the radius of the raised microstructures (310).
4. The flexible pressure sensor mimicking a neural synapse according to claim 1, characterized in that: The upper flexible substrate (100) and the lower flexible substrate (600) are made of polyethylene terephthalate (PET) or polyimide (PI) film.
5. The flexible pressure sensor mimicking a neural synapse according to claim 1, characterized in that: The upper electrode (200) and lower electrode (500) are conductive thin layers made of gold, metallic silver, or conductive silver paste.
6. A method for fabricating a flexible pressure sensor mimicking a neural synapse according to any one of claims 2-5, characterized in that, Includes the following steps: 1) Use 3D printing or photolithography-etching methods to fabricate an upper layer protruding microstructure (310) array mold and a lower layer cylindrical boss array mold; 2) Mix polydimethylsiloxane (PDMS) with a curing agent, stir magnetically, then add multi-walled carbon nanotubes to the mixture, stir magnetically, and disperse ultrasonically. 3) The prepared polydimethylsiloxane (PDMS) doped with multi-walled carbon nanotubes is poured into a mold, placed in a drying oven for heating and curing, and then peeled off from the mold to obtain the raised microstructure (310) of the upper sensitive layer (300) and the cylindrical boss array of the lower sensitive layer. 4) Using an ultraviolet laser, a three-dimensional porous graphene conductive layer (320) is generated on the surface of the protruding microstructure (310) of the upper sensitive layer (300) by laser induction. 5) Using a CO2 laser, laser ablation is performed on the cylindrical protrusions of the lower sensitive layer (400) to form an array of cylindrical recessed structures (420) and its secondary rough microstructures (410) on the surface. 6) Electrodes are formed on the surfaces of the upper flexible substrate (100) and the lower flexible substrate (600) by sputtering, vapor deposition or printing of conductive thin films; 7) Align and attach the lower flexible substrate (600) with the lower electrode (500), the lower sensitive layer (400), the upper sensitive layer (300), and the upper flexible substrate (100) with the upper electrode (200) in sequence, and apply glue around the perimeter to encapsulate it into a flexible pressure sensor that mimics a neural synapse.