Flexible proximity and pressure sensor based on fringe field effect and preparation method

Abstract

The invention particularly relates to a flexible proximity and pressure sensor based on a fringe field effect, which comprises an elastomer composite floating electrode, a composite dielectric layer, an interdigital electrode and an ultrathin flexible substrate, and is characterized in that the elastomer composite floating electrode is formed by compounding an elastomer electrode and a metal electrode; the elastomer electrode is an elastomer prepared from polydimethylsiloxane and a carbon nanotube composite material, and a multi-scale microstructure is formed on the outer surface, facing the composite dielectric layer, of the elastomer electrode; the metal electrode is a metal layer electrode evaporated on the outer surface of the elastomer electrode with the multi-scale microstructure; the composite dielectric layer is formed by compounding an organic dielectric layer and an inorganic metal oxide dielectric layer in an upper-lower layer structure, and the thickness of the composite dielectric layer is less than 220nm; the interdigital electrode adopts a coplanar design, the upper surface of the interdigital electrode is connected with the inorganic metal oxide dielectric layer in the composite dielectric layer, and the lower surface of the interdigital electrode is connected with hafnium oxide; the lower surface of the hafnium oxide is connected with the ultrathin flexible substrate, and the thickness of the ultrathin flexible substrate is smaller than 2 micrometers. According to the flexible proximity and pressure sensor based on the fringe field effect provided by the invention, the regulation and control capability on a fringe field is enhanced, the sensitivity and linearity of pressure sensing are improved while the proximity signal detection performance is not lost, the sensing range is expanded, and the interference of external electromagnetic signals on pressure detection is reduced.

Description

Technical Field

[0001] The 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 edge field effect are a new type of flexible sensor device that uses edge field effect to detect both proximity and pressure. This sensor with dual-function detection capability based on edge field effect is a capacitive sensor, which can generally convert proximity and pressure signals into changes in capacitance, and then detect both external proximity and pressure signals with only one device. Compared with other types of sensors, flexible capacitive sensors based on edge field effect have the characteristics 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 effect 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 vertical electrode structure design, the coplanar interdigitated electrode design has a certain degree of enhancement in the fringe field, which makes it suitable for detecting proximity signals. However, it is not sensitive in 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 change in the equivalent relative dielectric constant caused by external pressure is relatively limited, and the ability to regulate 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 electrode, which leads to a small change in capacitance, resulting in a very low sensor sensitivity. On the other hand, elastomeric dielectrics or elastomeric dielectrics with a single microstructure have the characteristics of material mechanics nonlinearity and contact mechanics nonlinearity due to their own material properties, so that their stress-strain curves show strong nonlinearity under large stresses, that is, under large pressures, the deformation caused by external pressure will be greatly reduced, which leads to a 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 easily affected by 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 regulation 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 solution of the present invention is as follows:

[0006] A flexible proximity and pressure sensor based on edge field effect, comprising an elastomer composite floating electrode, a composite dielectric layer, an interdigitated electrode, and an ultra-thin flexible substrate, characterized in that the elastomer composite floating electrode is composited by an elastomer electrode and a metal electrode, the elastomer electrode is an elastomer prepared from a composite material of polydimethylsiloxane and carbon nanotubes, and the elastomer electrode forms a multi-scale microstructure on the outer surface facing the composite dielectric layer; the metal electrode is a metal layer electrode evaporated on the outer surface of the elastomer electrode with the multi-scale microstructure; the composite dielectric layer is composited by an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, and the thickness is less than 220nm; the interdigitated electrode adopts a coplanar design, the upper surface of which is connected to the inorganic metal oxide dielectric layer in the composite dielectric layer, and the lower surface of which is connected to hafnium oxide; the lower surface of hafnium oxide is connected to the ultra-thin flexible substrate, and the thickness of the ultra-thin flexible substrate is less than 2μm.

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

[0008] Preferably, the ratio of the polydimethylsiloxane to the n-hexane solution is 1:5-1:10, the ratio of the carbon nanotubes to isopropanol is 1:200, and the ratio of the polydimethylsiloxane to the 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 from titanium-gold alloy or chromium-gold alloy by electron beam or thermal evaporation, the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm; the interdigitated electrode is obtained from titanium-gold alloy or chromium-gold alloy by electron beam or thermal evaporation, 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 polyparaxylene 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 above-mentioned flexible proximity and pressure sensor based on fringe field effect, the steps are as follows:

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

[0015] S2: Thermally deposit polyparaxylene or spin-coat polyimide on a low-resistance silicon wafer to obtain an ultra-thin flexible substrate with a thickness of 0.2-2 μm; atomically layer deposit 5 nm of hafnium oxide on the ultra-thin flexible substrate to increase the adhesion between the flexible substrate and the electrode, then evaporate interdigital electrodes on the hafnium oxide to make the interdigital electrodes coplanar, then atomically layer deposit aluminum oxide or yttrium oxide on the surface of the interdigital electrodes to obtain an inorganic metal oxide dielectric layer, and then thermally deposit polyparaxylene on the surface of the inorganic metal oxide dielectric layer or spin-coating polyimide, so that the inorganic metal oxide dielectric layer and the interdigital electrodes are completely covered by polyparaxylene or polyimide, the polyparaxylene or polyimide located on the upper surface of the inorganic metal oxide dielectric layer is used as an organic dielectric layer, and forms a composite dielectric layer with the inorganic metal oxide dielectric layer, and then the low-resistance silicon wafer and the ultra-thin flexible substrate are peeled off by electrochemical etching to obtain an organic dielectric layer, an inorganic metal oxide dielectric layer, an interdigital electrode and an ultra-thin flexible substrate connected in sequence from top to bottom;

[0016] S3: The elastomer composite floating electrode obtained in S1 is bonded to 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, and during the curing process, an irregular microstructure naturally appears on the surface of the mixed solution; or to etch a silicon wafer by photolithography to obtain a micro-pyramid structure mold of different sizes, and after the mold is hydrophobicized, pour the mixed solution of polydimethylsiloxane and carbon nanotubes into the mold and evacuate the substrate, and then heat and solidify it and 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 the detection of pressure signals and proximity signals or only for the detection of proximity signals, its elastomeric 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 the detection of pressure signals, any one side of it is fitted 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 edge field effect, comprising an elastomer composite floating electrode, a composite dielectric layer, an interdigitated electrode and an ultrathin flexible substrate, characterized in that the elastomer composite floating electrode is composited by an elastomer electrode and a metal electrode, the elastomer electrode is an elastomer prepared from a composite material of polydimethylsiloxane and carbon nanotubes, and the elastomer electrode forms a multi-scale microstructure on the outer surface facing the composite dielectric layer; the metal electrode is a metal layer electrode evaporated on the outer surface of the elastomer electrode with the multi-scale microstructure; the composite dielectric layer is composited by an organic dielectric layer and an inorganic metal oxide dielectric layer to form an upper and lower layer structure, and has a thickness of 30-220nm; the interdigitated electrode adopts a coplanar design, the upper surface of which is connected to the inorganic metal oxide dielectric layer in the composite dielectric layer, and the lower surface of which is connected to hafnium oxide; the lower surface of hafnium oxide is connected to the ultrathin flexible substrate, and the thickness of the ultrathin flexible substrate is 0.2-2μm.

[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 a forked electrode. Since the thickness of the ultra-thin flexible substrate is relatively small (0.2-2 μm), the fringe field generated by the forked electrode 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 the detection of proximity signals; in terms of pressure sensing, by constructing an organic dielectric layer and an inorganic dielectric layer on the surface of the forked 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 in the composite dielectric layer in contact with the microstructure surface. Since the thickness of the composite dielectric layer is very thin (30-220 nm), and the relative dielectric constant is larger 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 can effectively prevent the larger microstructure from entering the nonlinear region too early, and can effectively improve the sensing response range. In addition, the capacitance change of this scheme is mainly positively correlated with the contact area between the elastomer composite floating electrode microstructure and the composite dielectric layer, which effectively improves the linearity of the sensor. 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. 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 scheme 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 in combination 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 accompanying 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 limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effect that the present invention can produce and the purpose that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0024] The technical solution of the present invention is described in detail below in conjunction with 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 a forked electrode 3: a forked 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 comprises an elastomer composite floating electrode 1, a composite dielectric layer 2, and an interdigitated electrode 3, wherein the elastomer composite floating electrode 1 is composited by an elastomer electrode 12 and a metal electrode 13, wherein 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 13 formed by evaporation on the elastomer electrode 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, and the thickness is 30-220nm; the interdigitated electrode 31 adopts a coplanar design, and 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, and 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, and the thickness of the ultra-thin flexible substrate is 0.2-2μm.

[0026] In some embodiments of the present invention, the preparation method of the polydimethylsiloxane and carbon nanocomposite material for preparing the elastomeric composite floating electrode 1 is: mixing polydimethylsiloxane with a n-hexane solution, dispersing carbon nanotubes in isopropanol 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 isopropanol 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, the thickness of titanium is 5nm, and the thickness of gold is 50nm; in some embodiments of the present invention, the metal electrode 14 is obtained by thermal evaporation of titanium-gold alloy, the thickness of titanium is 5nm, and the thickness of gold is 50nm; in some embodiments of the present invention, the metal electrode 14 is obtained by electron beam evaporation of chromium-gold alloy, the thickness of chromium is 5nm, and the thickness of gold is 50nm; in some embodiments of the present invention, the metal electrode 14 is obtained by thermal evaporation of chromium-gold alloy, the thickness of chromium is 5nm, and the thickness of gold is 50nm.

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

[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 thickness of the ultra-thin flexible substrate 33 is 0.2 μm; in other embodiments of the present invention, the thickness of the ultra-thin flexible substrate 33 is 2 μm. In some embodiments of the present invention, the ultra-thin flexible substrate is obtained by thermally depositing polyparaxylene; 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 polyparaxylene or spin-coating polyimide on a low-resistance silicon wafer to obtain an upper flexible substrate 11, which is used to reduce 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 obtaining 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 titanium-gold alloy or chromium-gold alloy, that is, obtaining an elastomer composite floating electrode 1;

[0035] S2: thermally depositing polyparaxylene 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 to make the interdigital electrodes 31 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 poly on the inorganic gold oxide dielectric layer 22 and the surface of the hafnium oxide 32. Para-xylene or spin-coating polyimide, so that the poly-para-xylene or polyimide completely covers the inorganic metal oxide dielectric layer 22 and the hafnium oxide 31, and the part of the poly-para-xylene or polyimide located on the surface of the inorganic metal oxide dielectric layer 22 is used as the organic dielectric layer 21, and forms a composite dielectric layer 2 with the inorganic metal oxide dielectric layer 22, and then the low-resistance silicon wafer and the ultra-thin flexible substrate 33 are peeled off by electrochemical etching, so as to obtain the organic dielectric layer 21, the inorganic metal oxide dielectric layer 22, the interdigital electrode 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 interdigital 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 edge field effect.

[0037] In some embodiments of the present invention, the method for forming the multi-scale microstructure 13 refers to drop-coating a mixed solution of polydimethylsiloxane and carbon nanotubes onto a hydrophobic substrate, evacuating the solution and then heating and curing it, and 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 refers to etching a silicon wafer by photolithography to obtain micro-pyramid structure molds of different sizes, after the mold is hydrophobicized, pouring the mixed solution of polydimethylsiloxane and carbon nanotubes into the mold and evacuating the solution, heating and curing it, and then peeling off the mold 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 edge field effect is: when the flexible proximity and pressure sensor based on edge field effect is used for detecting pressure signals and proximity signals, its elastomeric composite floating electrode is fitted with the object to be fixed; when the flexible proximity and pressure sensor based on edge field effect is only used for detecting proximity signals, its elastomeric composite floating electrode is fitted with the object to be fixed; when the flexible proximity and pressure sensor based on edge 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 edge field effect provided by the present invention can be used to detect proximity signals and pressure signals at the same time. In terms of pressure sensing, by constructing an organic dielectric layer 21 and an inorganic dielectric layer 22 on the surface 31 of the interdigitated electrode to form a composite dielectric layer 2 composed of an upper and lower structure, and using an elastomer composite floating electrode 1 with a multi-scale microstructure 13 as a pressure-sensitive floating electrode, the relatively weak edge field can be effectively localized in the composite dielectric layer 2 in contact with the surface of the microstructure 13. Since the thickness of the composite dielectric layer 2 is very small (30-220nm) and the relative dielectric constant is larger than that of a single elastomer dielectric layer, the control ability of the edge 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 13 can effectively prevent the larger microstructure from entering the nonlinear region too early, and can effectively improve the sensing response range. And the capacitance change of this scheme is mainly positively correlated with the contact area between the elastomer composite floating electrode microstructure 13 and the composite dielectric layer 2, which effectively improves the linearity of the sensor.

[0040] In terms of proximity sensing, the present invention utilizes an ultra-thin flexible substrate 33 to construct the interdigital 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 interdigital 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, the interference of external electromagnetic signals on pressure detection can be reduced to a certain extent.

[0042] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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-mentioned embodiment only expresses one implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A flexible proximity and pressure sensor based on fringe field effect, comprising an elastomer composite floating electrode, a composite dielectric layer, an interdigitated electrode, and an ultra-thin flexible substrate, characterized in that: The elastomer composite floating electrode is composed of an elastomer electrode and a metal electrode. The elastomer electrode is an elastomer made of a composite material of polydimethylsiloxane and carbon nanotubes. The elastomer electrode forms a multi-scale microstructure on the outer surface facing the composite dielectric layer. The metal electrode is a metal layer electrode evaporated on the outer surface of the elastomer 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, and the thickness is less than 220nm. The interdigitated electrode adopts a coplanar design, and its upper surface is connected to the inorganic metal oxide dielectric layer in the composite dielectric layer, and its lower surface is 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: mixing polydimethylsiloxane with a normal hexane solution, dispersing carbon nanotubes in isopropanol 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 isopropanol 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-gold alloy or chromium-gold alloy, the thickness of titanium or chromium is 5nm, and the thickness of gold is 50nm; the interdigital electrode is obtained by electron beam or thermal evaporation of titanium-gold alloy or chromium-gold alloy, the thickness of titanium or chromium is 5nm, and the thickness of 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 polyparaxylene 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 polyparaxylene 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 polyparaxylene or spin-coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate, and then peeling off the low-resistance silicon wafer to obtain an upper flexible substrate for reducing the viscosity of the surface of the elastomer electrode; using a mixed solution of polydimethylsiloxane and carbon nanotubes to prepare an elastomer electrode; forming a multi-scale microstructure on the outer surface of the elastomer electrode facing the composite dielectric layer, and obtaining a metal layer electrode by electron beam or thermal evaporation of titanium-gold alloy or chromium-gold alloy on the outer surface of the elastomer electrode having the multi-scale microstructure, that is, obtaining an elastomer composite floating electrode; S2: Thermally deposit polyparaxylene or spin-coat polyimide on a low-resistance silicon wafer to obtain an ultra-thin flexible substrate with a thickness of 0.2-2 μm; atomically layer deposit 5 nm of hafnium oxide on the ultra-thin flexible substrate to increase the adhesion between the flexible substrate and the electrode, then evaporate interdigital electrodes on the hafnium oxide to make the interdigital electrodes coplanar, then atomically layer deposit aluminum oxide or yttrium oxide on the surface of the interdigital electrodes to obtain an inorganic metal oxide dielectric layer, and then thermally deposit polyparaxylene on the surface of the inorganic metal oxide dielectric layer or spin-coating polyimide, so that the inorganic metal oxide dielectric layer and the interdigital electrodes are completely covered by polyparaxylene or polyimide, the polyparaxylene or polyimide located on the upper surface of the inorganic metal oxide dielectric layer is used as an organic dielectric layer, and forms a composite dielectric layer with the inorganic metal oxide dielectric layer, and then the low-resistance silicon wafer and the ultra-thin flexible substrate are peeled off by electrochemical etching to obtain an organic dielectric layer, an inorganic metal oxide dielectric layer, an interdigital electrode and an ultra-thin flexible substrate connected in sequence from top to bottom; S3: The elastomer composite floating electrode obtained in S1 is bonded to 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 solidify it, and during the curing process of the mixed solution, an irregular microstructure naturally appears on the surface; Alternatively, a silicon wafer is 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 evacuated. 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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