A flexible proximity and pressure sensor based on fringe field effect and its preparation method

Abstract

The present invention specifically relates to a flexible proximity and pressure sensor based on fringe field effect, comprising an elastomeric composite floating electrode, a composite dielectric layer, interdigitated electrodes, and an ultrathin flexible substrate. The sensor is characterized in that the elastomeric composite floating electrode is composed of an elastomeric electrode and a metal electrode, wherein the elastomeric electrode is an elastomer made of a composite material of polydimethylsiloxane and carbon nanotubes, and a multi-scale microstructure is formed on the outer surface of the elastomeric electrode facing the composite dielectric layer. The metal electrode is a metal layer electrode evaporated on the outer surface of the elastomeric electrode having the multi-scale microstructure. The composite dielectric layer is composed of an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, and has a thickness of less than 220 nm. The interdigitated electrodes are coplanar in design, with their upper surface connected to the inorganic metal oxide dielectric layer in the composite dielectric layer and their lower surface connected to hafnium oxide. The lower surface of the hafnium oxide is connected to the ultrathin flexible substrate, and the thickness of the ultrathin flexible substrate is less than 2 μm. The flexible proximity and pressure sensor based on fringe field effect provided by the present invention enhances the ability to regulate the fringe field, improves the sensitivity and linearity of pressure sensing without sacrificing the performance of proximity signal detection, expands the sensing range, and reduces the interference of external electromagnetic signals on pressure detection.

Description

Technical Field

[0001] The present invention relates to the field of capacitive sensors, and in particular to a flexible proximity and pressure sensor based on fringe field effect and a preparation method thereof. Background Art

[0002] Flexible proximity and pressure sensors based on the fringe field effect are a new type of flexible sensor device that utilizes the fringe field effect to simultaneously detect two physical quantities: proximity and pressure. This dual-function sensor based on the fringe field effect is a capacitive sensor that generally converts proximity and pressure signals into changes in capacitance, thereby enabling detection of both external proximity and pressure signals using a single device. Compared to other types of sensors, flexible capacitive sensors based on the fringe field effect have the advantages of low power consumption, compact device structure, and the ability to detect both proximity and pressure signals. They have broad application prospects in emerging fields such as human-computer interaction, humanoid robots, electric vehicles, and implantable physiological signal detection.

[0003] Existing designs of flexible proximity and pressure sensors based on fringe field effects include a design that uses a typical elastomeric dielectric or an elastomeric dielectric with a single microstructure as a mechanical sensitive element and then laminates it on coplanar interdigitated electrodes. Compared with the perpendicular electrode structure, this coplanar interdigitated electrode design enhances the fringe field to a certain extent, making it suitable for detecting proximity signals. However, it is not sensitive when detecting pressure signals and has a limited sensing range. The reasons are as follows: On the one hand, due to the relatively low relative dielectric constant of typical elastomeric dielectrics, the equivalent relative dielectric constant change caused by external pressure is relatively limited, and the ability to control the fringe field is relatively weak. At the same time, the fringe field itself is weaker than the uniform electric field strength perpendicular to the electrodes, which leads to a small change in capacitance, resulting in low sensor sensitivity. On the other hand, elastomeric dielectrics or elastomeric dielectrics with a single microstructure have material mechanics and contact mechanics nonlinearities due to their inherent material properties. Their stress-strain curves exhibit strong nonlinearity under high stress. That is, under high pressure, the deformation caused by external pressure is greatly reduced, resulting in relatively low linearity of the sensor response and a relatively narrow sensing range. In addition, existing fringe field-based proximity and pressure sensor designs are also susceptible to electromagnetic interference. Summary of the Invention

[0004] The present invention solves the problems of existing flexible proximity and pressure sensors based on fringe field effect in pressure sensing, such as relatively weak fringe field control ability, relatively low sensing sensitivity and linearity, relatively narrow sensing range, and susceptibility to electromagnetic interference. In order to solve the above problems without losing proximity sensing performance, the present invention provides a flexible proximity and pressure sensor based on fringe field effect.

[0005] The technical solutions of the present invention are as follows:

[0006] A flexible proximity and pressure sensor based on fringe field effect, comprising an elastomeric composite floating electrode, a composite dielectric layer, interdigitated electrodes, and an ultrathin flexible substrate. The elastomeric composite floating electrode is composed of an elastomeric electrode and a metal electrode, wherein the elastomeric electrode is an elastomer made of a composite material of polydimethylsiloxane and carbon nanotubes, and a multi-scale microstructure is formed on the outer surface of the elastomeric electrode facing the composite dielectric layer. The metal electrode is a metal layer electrode evaporated onto the outer surface of the elastomeric electrode having the multi-scale microstructure. The composite dielectric layer is composed of an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, and has a thickness of less than 220 nm. The interdigitated electrodes are coplanar in design, with their upper surface connected to the inorganic metal oxide dielectric layer in the composite dielectric layer and their lower surface connected to hafnium oxide. The lower surface of the hafnium oxide is connected to the ultrathin flexible substrate, and the thickness of the ultrathin flexible substrate is less than 2 μm.

[0007] Preferably, the preparation method of the polydimethylsiloxane and carbon nanocomposite material is: mixing polydimethylsiloxane with n-hexane solution, dispersing carbon nanotubes in isopropanol by water bath ultrasound, and finally mixing the two mixed solutions.

[0008] Preferably, the ratio of polydimethylsiloxane to n-hexane solution is 1:5-1:10, the ratio of carbon nanotubes to isopropyl alcohol is 1:200, and the ratio of polydimethylsiloxane to carbon nanotubes is 100:1-100:5.

[0009] Preferably, the multi-scale microstructure is a plurality of irregular three-dimensional structures or a plurality of micro-pyramid structures of different sizes.

[0010] Preferably, the metal electrode is obtained by electron beam or thermal evaporation of titanium or chromium-gold alloy, the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm; the interdigitated electrode is obtained by electron beam or thermal evaporation of titanium or chromium-gold alloy, the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 25-30nm.

[0011] Preferably, the organic dielectric layer is made of parylene or polyimide, and has a thickness of 20-200 nm; the inorganic metal oxide dielectric layer is made of aluminum oxide or yttrium oxide, and has a thickness of 10-20 nm.

[0012] Preferably, the ultra-thin flexible substrate is obtained by thermally depositing parylene or spin coating polyimide.

[0013] The present invention also provides a method for preparing the flexible proximity and pressure sensor based on the fringe field effect, comprising the following steps:

[0014] S1: thermally depositing parylene or spin-coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate, then peeling off the low-resistance silicon wafer to obtain an upper flexible substrate for reducing the stickiness of the elastomer electrode surface; using a mixed solution of polydimethylsiloxane and carbon nanotubes to prepare the elastomer electrode; forming a multi-scale microstructure on the outer surface of the elastomer electrode facing the composite dielectric layer, and electron beam or thermal evaporation depositing a titanium-gold alloy or a chromium-gold alloy on the outer surface of the elastomer electrode having the multi-scale microstructure to obtain a lower metal layer electrode, thereby obtaining an elastomer composite floating electrode;

[0015] S2: Thermally depositing parylene or spin-coating polyimide on a low-resistance silicon wafer to obtain an ultra-thin flexible substrate with a thickness of 0.2-2 μm; atomically layer depositing 5 nm hafnium oxide on the ultra-thin flexible substrate to increase the adhesion between the flexible substrate and the electrode, then evaporating interdigital electrodes on the hafnium oxide to make the interdigital electrodes coplanar, then atomically layer depositing aluminum oxide or yttrium oxide on the surface of the interdigital electrodes to obtain an inorganic metal oxide dielectric layer, and then thermally depositing parylene on the surface of the inorganic metal oxide dielectric layer Alternatively, polyimide is spin-coated to completely cover the inorganic metal oxide dielectric layer and the interdigitated electrodes with parylene or polyimide. The parylene or polyimide on the upper surface of the inorganic metal oxide dielectric layer serves as an organic dielectric layer, forming a composite dielectric layer with the inorganic metal oxide dielectric layer. The low-resistance silicon wafer is then peeled off from the ultra-thin flexible substrate by electrochemical etching, thereby obtaining an organic dielectric layer, an inorganic metal oxide dielectric layer, an interdigitated electrode, and an ultra-thin flexible substrate connected in sequence from top to bottom.

[0016] S3: Laminating the elastomer composite floating electrode obtained in S1 and the composite dielectric layer, the interdigitated electrode and the ultra-thin flexible substrate obtained in S2, so that the outer surface of the elastomer composite floating electrode having a multi-scale microstructure is connected to the organic dielectric layer in the composite dielectric layer, thereby obtaining a flexible proximity and pressure sensor based on the edge field effect.

[0017] Preferably, the method for forming the multi-scale microstructure in S1 is to drop-coat a mixed solution of polydimethylsiloxane and carbon nanotubes onto a hydrophobic substrate, evacuate the substrate, and heat and solidify it, wherein irregular microstructures naturally appear on the surface of the mixed solution during the curing process; or to etch a silicon wafer by photolithography to obtain a mold of micro-pyramid structures of different sizes, treat the mold hydrophobically, pour the mixed solution of polydimethylsiloxane and carbon nanotubes into the mold, evacuate the substrate, heat and solidify it, and then peel off the mold to obtain micro-pyramid structures of different sizes.

[0018] Preferably, when the flexible proximity and pressure sensor based on the fringe field effect is used for detecting pressure signals and proximity signals or only for detecting proximity signals, its elastomer composite floating electrode is adhered to the object to be fixed; when the flexible proximity and pressure sensor based on the fringe field effect is only used for detecting pressure signals, any one side of it is adhered to the object to be fixed.

[0019] The beneficial effects of the present invention are as follows:

[0020] A flexible proximity and pressure sensor based on fringe field effect, comprising an elastomeric composite floating electrode, a composite dielectric layer, interdigitated electrodes, and an ultrathin flexible substrate. The elastomeric composite floating electrode is composed of an elastomeric electrode and a metal electrode, wherein the elastomeric electrode is an elastomer made of a composite material of polydimethylsiloxane and carbon nanotubes, and a multi-scale microstructure is formed on the outer surface of the elastomeric electrode facing the composite dielectric layer. The metal electrode is a metal layer electrode evaporated onto the outer surface of the elastomeric electrode having the multi-scale microstructure. The composite dielectric layer is composed of an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, and has a thickness of 30-220 nm. The interdigitated electrodes are coplanar in design, with their upper surface connected to the inorganic metal oxide dielectric layer in the composite dielectric layer and their lower surface connected to hafnium oxide. The lower surface of the hafnium oxide is connected to the ultrathin flexible substrate, and the thickness of the ultrathin flexible substrate is 0.2-2 μm.

[0021] The flexible proximity and pressure sensor based on the fringe field effect of the present invention can be used to detect proximity signals and pressure signals at the same time without losing proximity sensing performance. In terms of proximity sensing, the present invention uses an ultra-thin flexible substrate to construct interdigitated electrodes. Since the thickness of the ultra-thin flexible substrate is relatively small (0.2-2μm), the fringe field generated by the interdigitated electrodes on the back of the ultra-thin flexible substrate is basically unaffected, that is, compared with the vertical electrode structure, this scheme can still achieve proximity signal detection; in terms of pressure sensing, by constructing an organic dielectric layer and an inorganic dielectric layer on the surface of the interdigitated electrode to form a composite dielectric layer composed of an upper and lower structure, and using an elastomeric composite electrode with a multi-scale microstructure as a pressure-sensitive floating electrode, the relatively weak fringe field can be effectively localized to the composite dielectric layer in contact with the microstructure surface. Since the composite dielectric layer is very thin (30-220nm) and has a relative dielectric constant greater than that of the elastomeric dielectric layer, the control ability of the fringe field and the change in capacitance can be greatly improved, that is, the sensitivity of the sensing response can be greatly improved. The multi-scale microstructure effectively prevents larger microstructures from prematurely entering the nonlinear region, effectively extending the sensor response range. Furthermore, the capacitance change in this scheme is positively correlated with the contact area between the elastomer composite floating electrode microstructure and the composite dielectric layer, effectively improving the sensor's linearity. Furthermore, the floating electrode's inherent electromagnetic shielding properties can reduce interference from external electromagnetic signals on pressure detection to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 : Structural diagram of flexible proximity and pressure sensor based on fringe field effect. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the flexible proximity and pressure sensor based on the edge field effect proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings. It should be noted that the structure, proportion, size, etc. illustrated in the drawings of this specification are only used to match the content disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the implementation conditions of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0024] The technical solution of the present invention is described in detail below with reference to the accompanying drawings. The present invention provides a flexible pressure sensor with integrated carbon nanotube transistors, such as Figure 1 As shown, it includes: an elastomer composite floating electrode 1: an upper flexible substrate 11, an elastomer electrode 12 composed of a composite material, a multi-scale microstructure 13 formed on the outer surface of the elastomer electrode facing the composite dielectric layer, a metal layer electrode 14 evaporated on the surface of the multi-scale microstructure, a composite dielectric layer 2: an organic dielectric layer 21, an inorganic metal oxide dielectric layer 22, and an interdigitated electrode 3: an interdigitated electrode 31, hafnium oxide 32, and an ultra-thin flexible substrate 33.

[0025] In some embodiments of the present invention, the flexible proximity and pressure sensor based on the edge field effect includes an elastomer composite floating electrode 1, a composite dielectric layer 2, and an interdigitated electrode 3, characterized in that the elastomer composite floating electrode 1 is composed of an elastomer electrode 12 and a metal electrode 13, the elastomer electrode 12 is an elastomer prepared from a composite material of polydimethylsiloxane and carbon nanotubes, and the elastomer electrode 12 forms a multi-scale microstructure 13 on the outer surface facing the composite dielectric layer 2; the metal electrode is a multi-scale microstructure formed on the elastomer electrode by evaporation. The metal layer electrode 14 on the outer surface; the composite dielectric layer 2 is composed of an organic dielectric layer 21 and an inorganic metal oxide dielectric layer 22 to form an upper and lower layer structure, with a thickness of 30-220nm; the interdigitated electrode 31 adopts a coplanar design, its upper surface is connected to the inorganic metal oxide dielectric layer 22 in the composite dielectric layer 2, and its lower surface is connected to the hafnium oxide 32. The hafnium oxide 32 is used to increase the adhesion between the interdigitated electrode 31 and the ultra-thin flexible substrate 33, and its lower surface is connected to the ultra-thin flexible substrate 33. The thickness of the ultra-thin flexible substrate is 0.2-2μm.

[0026] In some embodiments of the present invention, the polydimethylsiloxane and carbon nanocomposite material used to prepare the elastomeric composite floating electrode 1 is prepared by mixing polydimethylsiloxane with a n-hexane solution, dispersing carbon nanotubes in isopropyl alcohol by water bath ultrasound, and finally mixing the two solutions.

[0027] In some embodiments of the present invention, the ratio of polydimethylsiloxane to n-hexane solution is 1:5-1:10, the ratio of carbon nanotubes to isopropyl alcohol is 1:200, and the ratio of polydimethylsiloxane to carbon nanotubes is 100:1-100:5.

[0028] In some embodiments of the present invention, the multi-scale microstructure 13 is a plurality of irregular three-dimensional structures; in some embodiments of the present invention, the multi-scale microstructure 13 is one or more micro-pyramid structures of different sizes.

[0029] In some embodiments of the present invention, the metal electrode 14 is obtained by electron beam evaporation of titanium-gold alloy, and the thickness of the titanium is 5 nm, and the thickness of the gold is 50 nm; in some embodiments of the present invention, the metal electrode 14 is obtained by thermal evaporation of titanium-gold alloy, and the thickness of the titanium is 5 nm, and the thickness of the gold is 50 nm; in some embodiments of the present invention, the metal electrode 14 is obtained by electron beam evaporation of chromium-gold alloy, and the thickness of the chromium is 5 nm, and the thickness of the gold is 50 nm; in some embodiments of the present invention, the metal electrode 14 is obtained by thermal evaporation of chromium-gold alloy, and the thickness of the chromium is 5 nm, and the thickness of the gold is 50 nm.

[0030] In some embodiments of the present invention, the interdigitated electrodes 31 are obtained by electron beam evaporation of titanium-gold alloy, and the thickness of the titanium is 5 nm, and the thickness of the gold is 25 nm; in other embodiments of the present invention, the interdigitated electrodes 31 are obtained by electron beam evaporation of chromium-gold alloy, and the thickness of the chromium is 5 nm, and the thickness of the gold is 25 nm; in some embodiments of the present invention, the interdigitated electrodes 31 are obtained by overheating evaporation of titanium-gold alloy, and the thickness of the titanium is 5 nm, and the thickness of the gold is 30 nm; in other embodiments of the present invention, the interdigitated electrodes 31 are obtained by overheating evaporation of chromium-gold alloy, and the thickness of the chromium is 5 nm, and the thickness of the gold is 30 nm.

[0031] In some embodiments of the present invention, the organic dielectric layer 21 in the composite dielectric layer 2 is made of polyparaxylene; in other embodiments of the present invention, the organic dielectric layer 21 in the composite dielectric layer 2 is made of polyimide; in some embodiments of the present invention, the inorganic metal oxide dielectric layer 22 is made of aluminum oxide; in other embodiments of the present invention, the inorganic metal oxide dielectric layer 22 is made of yttrium oxide; in some embodiments of the present invention, the thickness of the organic dielectric layer 21 is 20 nm, the thickness of the inorganic metal oxide dielectric layer 22 is 10 nm, and the thickness of the composite dielectric layer 2 is 30 nm; in other embodiments of the present invention, the thickness of the organic dielectric layer 21 is 200 nm, the thickness of the inorganic metal oxide dielectric layer 22 is 20 nm, and the thickness of the composite dielectric layer 2 is 220 nm.

[0032] In some embodiments of the present invention, the ultra-thin flexible substrate 33 has a thickness of 0.2 μm; in other embodiments of the present invention, the ultra-thin flexible substrate 33 has a thickness of 2 μm. In some embodiments of the present invention, the ultra-thin flexible substrate is obtained by thermally depositing parylene; in some embodiments of the present invention, the ultra-thin flexible substrate is obtained by or spin coating polyimide.

[0033] In some embodiments of the present invention, a method for preparing a flexible proximity and pressure sensor based on fringe field effect comprises the following steps:

[0034] S1: thermally depositing parylene or spin-coating polyimide on a low-resistance silicon wafer to obtain an upper flexible substrate 11 for reducing the viscosity of the surface of the elastomer electrode 12; using a mixed solution of polydimethylsiloxane and carbon nanotubes to prepare the elastomer electrode 12; forming a multi-scale microstructure 13 on the outer surface of the elastomer electrode facing the composite dielectric layer; and forming a metal layer electrode 14 on the outer surface of the elastomer electrode 12 having the multi-scale microstructure 13 by electron beam or thermal evaporation of a titanium-gold alloy or a chromium-gold alloy, thereby obtaining an elastomer composite floating electrode 1;

[0035] S2: Thermally depositing parylene or spin-coating flexible polyimide on a low-resistance silicon wafer to obtain an ultra-thin flexible substrate 33 with a thickness of 0.2-2 μm; atomically layer depositing hafnium oxide 32 with a thickness of 5 nm on the ultra-thin flexible substrate 33 to increase the adhesion between the ultra-thin flexible substrate 33 and the interdigital electrodes 31, and depositing the interdigital electrodes 31 on the surface of the hafnium oxide 32 so that the interdigital electrodes 31 are coplanar; then atomically layer depositing aluminum oxide or yttrium oxide on the surface of the interdigital electrodes 31 to obtain an inorganic metal oxide dielectric layer 22, and then thermally depositing polyimide on the inorganic metal oxide dielectric layer 22 and the surface of the hafnium oxide 32. Parylene or polyimide is spin-coated to completely cover the inorganic metal oxide dielectric layer 22 and hafnium oxide 31. The portion of parylene or polyimide located on the surface of the inorganic metal oxide dielectric layer 22 serves as the organic dielectric layer 21, forming a composite dielectric layer 2 with the inorganic metal oxide dielectric layer 22. The low-resistance silicon wafer and the ultra-thin flexible substrate 33 are then peeled off by electrochemical etching to obtain the organic dielectric layer 21, the inorganic metal oxide dielectric layer 22, the interdigitated electrodes 31, the hafnium oxide 32, and the ultra-thin flexible substrate 33 connected in sequence from top to bottom.

[0036] S3: Laminating the elastomeric composite floating electrode 1 obtained in S1 and the composite dielectric layer 2 and the interdigitated electrode 3 obtained in S2, so that the outer surface of the elastomeric composite floating electrode 1 having the multi-scale microstructure 13 contacts the organic dielectric layer 21 in the composite dielectric layer 2, thereby obtaining a flexible proximity and pressure sensor based on the fringe field effect.

[0037] In some embodiments of the present invention, the method for forming the multi-scale microstructure 13 is to drop-coat a mixed solution of polydimethylsiloxane and carbon nanotubes onto a hydrophobic substrate, evacuate the solution, and heat and solidify it. During the curing process, irregular microstructures naturally appear on the surface of the mixed solution. In other embodiments of the present invention, the method for forming the multi-scale microstructure 13 is to etch a silicon wafer by photolithography to obtain a micro-pyramid structure mold of different sizes. After the mold is hydrophobicized, the mixed solution of polydimethylsiloxane and carbon nanotubes is poured into the mold and evacuated. After heating and solidifying, the mold is peeled off to obtain micro-pyramid structures of different sizes.

[0038] In some embodiments of the present invention, the preparation method of the above-mentioned flexible proximity and pressure sensor based on fringe field effect is: when the flexible proximity and pressure sensor based on fringe field effect is used for detecting pressure signals and proximity signals, its elastomer composite floating electrode is fitted with the object to be fixed; when the flexible proximity and pressure sensor based on fringe field effect is only used for detecting proximity signals, its elastomer composite floating electrode is fitted with the object to be fixed; when the flexible proximity and pressure sensor based on fringe field effect is only used for detecting pressure signals, any one side of it is fitted with the object to be fixed.

[0039] The flexible proximity and pressure sensor based on the fringe field effect provided by the present invention can be used to detect both proximity and pressure signals. Regarding pressure sensing, a composite dielectric layer 2 is formed by constructing an organic dielectric layer 21 and an inorganic dielectric layer 22 on the interdigitated electrode surface 31, and an elastomeric composite floating electrode 1 with multi-scale microstructures 13 is used as the pressure-sensitive floating electrode. This effectively localizes the relatively weak fringe field to the composite dielectric layer 2 in contact with the surface of the microstructures 13. Because the composite dielectric layer 2 has a very small thickness (30-220 nm) and a greater relative dielectric constant than a single elastomeric dielectric layer, it significantly enhances the controllability of the fringe field and the capacitance change, thereby significantly improving the sensitivity of the sensor response. The multi-scale microstructures 13 effectively prevent larger microstructures from prematurely entering the nonlinear region, effectively extending the sensor response range. Furthermore, the capacitance change in this solution is positively correlated with the contact area between the elastomeric composite floating electrode microstructures 13 and the composite dielectric layer 2, effectively improving the linearity of the sensor.

[0040] In terms of proximity sensing, the present invention utilizes an ultra-thin flexible substrate 33 to construct interdigitated electrodes 31. Since the thickness of the ultra-thin flexible substrate 33 is relatively small (0.2-2 μm), the fringe field generated by the interdigitated electrodes 31 on the back side of the ultra-thin flexible substrate 33 is basically unaffected. Compared with the vertical electrode structure, this solution can still realize the detection of proximity signals.

[0041] In addition, since the floating electrode itself has an electromagnetic shielding effect, it can reduce the interference of external electromagnetic signals on pressure detection to a certain extent.

[0042] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0043] The above-described embodiment merely represents one embodiment of the present invention. While the description is relatively specific and detailed, it should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A flexible proximity and pressure sensor based on fringe field effect, comprising an elastomer composite floating electrode, a composite dielectric layer, interdigitated electrodes, and an ultrathin flexible substrate, characterized in that: The elastomeric composite floating electrode is composed of an elastomeric electrode and a metal electrode. The elastomeric electrode is an elastomer made of a composite material of polydimethylsiloxane and carbon nanotubes, and the elastomeric electrode has a multi-scale microstructure formed on its outer surface facing the composite dielectric layer. The metal electrode is a metal layer electrode evaporated on the outer surface of the elastomeric electrode with the multi-scale microstructure. The composite dielectric layer is composed of an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, with a thickness of less than 220nm. The interdigitated electrodes adopt a coplanar design, with their upper surface connected to the inorganic metal oxide dielectric layer in the composite dielectric layer and their lower surface connected to hafnium oxide. The lower surface of the hafnium oxide is connected to an ultra-thin flexible substrate, and the thickness of the ultra-thin flexible substrate is less than 2μm.

2. The flexible proximity and pressure sensor based on fringe field effect according to claim 1, characterized in that: The preparation method of the polydimethylsiloxane and carbon nanocomposite material comprises the following steps: mixing polydimethylsiloxane with a n-hexane solution, dispersing carbon nanotubes in isopropyl alcohol by water bath ultrasound, and finally mixing the two mixed solutions.

3. The flexible proximity and pressure sensor based on fringe field effect according to claim 2, characterized in that: The ratio of the polydimethylsiloxane to the n-hexane solution is 1:5-1:10, the ratio of the carbon nanotubes to the isopropyl alcohol is 1:200, and the ratio of the polydimethylsiloxane to the carbon nanotubes is 100:1-100:

5.

4. The flexible proximity and pressure sensor based on fringe field effect according to claim 1, characterized in that The multi-scale microstructure is a plurality of irregular three-dimensional structures or a plurality of micro-pyramid structures of different sizes.

5. The flexible proximity and pressure sensor based on fringe field effect according to claim 1, characterized in that The metal electrode is obtained by electron beam or thermal evaporation of titanium or chromium-gold alloy, the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm; the interdigitated electrode is obtained by electron beam or thermal evaporation of titanium or chromium-gold alloy, the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 25-30nm.

6. The flexible proximity and pressure sensor based on fringe field effect according to claim 1, characterized in that: The organic dielectric layer is made of parylene or polyimide and has a thickness of 20-200 nm. The inorganic metal oxide dielectric layer is made of aluminum oxide or yttrium oxide and has a thickness of 10-20 nm.

7. The flexible proximity and pressure sensor based on fringe field effect according to any one of claims 1 to 6, characterized in that: The ultra-thin flexible substrate is obtained by thermally depositing parylene or spin-coating polyimide.

8. The method for preparing the flexible proximity and pressure sensor based on fringe field effect according to any one of claims 1 to 7, comprising the following steps: S1: thermally depositing parylene or spin-coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate, then peeling off the low-resistance silicon wafer to obtain an upper flexible substrate for reducing the stickiness of the surface of the elastomer electrode; using a mixed solution of polydimethylsiloxane and carbon nanotubes to prepare the elastomer electrode; forming a multi-scale microstructure on the outer surface of the elastomer electrode facing the composite dielectric layer, and electron beam or thermal evaporation depositing a titanium-gold alloy or a chromium-gold alloy on the outer surface of the elastomer electrode having the multi-scale microstructure to obtain a metal layer electrode, thereby obtaining an elastomer composite floating electrode; S2: Thermally depositing parylene or spin-coating polyimide on a low-resistance silicon wafer to obtain an ultra-thin flexible substrate with a thickness of 0.2-2 μm; atomically layer depositing 5 nm hafnium oxide on the ultra-thin flexible substrate to increase the adhesion between the flexible substrate and the electrode, then evaporating interdigital electrodes on the hafnium oxide to make the interdigital electrodes coplanar, then atomically layer depositing aluminum oxide or yttrium oxide on the surface of the interdigital electrodes to obtain an inorganic metal oxide dielectric layer, and then thermally depositing parylene on the surface of the inorganic metal oxide dielectric layer Alternatively, polyimide is spin-coated to completely cover the inorganic metal oxide dielectric layer and the interdigitated electrodes with parylene or polyimide. The parylene or polyimide on the upper surface of the inorganic metal oxide dielectric layer serves as an organic dielectric layer, forming a composite dielectric layer with the inorganic metal oxide dielectric layer. The low-resistance silicon wafer is then peeled off from the ultra-thin flexible substrate by electrochemical etching, thereby obtaining an organic dielectric layer, an inorganic metal oxide dielectric layer, an interdigitated electrode, and an ultra-thin flexible substrate connected in sequence from top to bottom. S3: Laminating the elastomer composite floating electrode obtained in S1 and the composite dielectric layer, the interdigitated electrode and the ultra-thin flexible substrate obtained in S2, so that the outer surface of the elastomer composite floating electrode having a multi-scale microstructure is connected to the organic dielectric layer in the composite dielectric layer, thereby obtaining a flexible proximity and pressure sensor based on the edge field effect.

9. The preparation method according to claim 8, characterized in that The method for forming the multi-scale microstructure in S1 is to drop-coat a mixed solution of polydimethylsiloxane and carbon nanotubes onto a hydrophobic substrate, evacuate the solution, and heat and cure it. During the curing process of the mixed solution, irregular microstructures naturally appear on the surface. Alternatively, silicon wafers are etched through photolithography to obtain micro-pyramid structure molds of different sizes. After the mold is hydrophobicized, a mixed solution of polydimethylsiloxane and carbon nanotubes is poured into the mold and vacuumed. After heating and curing, the mold is peeled off to obtain micro-pyramid structures of different sizes.

10. The method for using the flexible proximity and pressure sensor based on fringe field effect according to any one of claims 1 to 7, characterized in that: When the flexible proximity and pressure sensor based on the fringe field effect is used for detecting pressure signals and proximity signals or only for detecting proximity signals, its elastomer composite floating electrode is fitted to the object to be fixed; when the flexible proximity and pressure sensor based on the fringe field effect is only used for detecting pressure signals, any one side of it is fitted to the object to be fixed.

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