Fringing field-based floating gate carbon nanotube transistor flexible pressure sensor and preparation method thereof

Abstract

The invention provides a floating gate carbon nanotube transistor flexible pressure sensor based on a fringing field. The floating gate carbon nanotube transistor flexible pressure sensor comprises an elastomer composite electrode, a layered composite dielectric layer, an interdigital electrode, a floating gate carbon nanotube transistor and a flexible substrate, the elastomer composite electrode comprises an elastomer electrode and a metal electrode; the elastomer electrode is prepared from a PDMS and CNT composite material, and a multi-scale microstructure is formed on the outer surface of the elastomer electrode; the metal electrode is evaporated on the outer surface of the multi-scale microstructure; the layered composite dielectric substance layer comprises an organic dielectric substance and an inorganic dielectric substance; the interdigital electrodes are in coplanar design, and one electrode extends out of the elastomer composite electrode in the direction opposite to the non-extended electrode to serve as a floating gate electrode; and the transistor dielectric layer, the channel and the source and drain electrodes are positioned on the extended part of the delay electrode outside the elastomer composite electrode. According to the invention, the regulation and control capability on a fringing field is enhanced, the sensitivity and mechanical stability of the sensor are greatly improved, the working voltage is reduced, and array expansion is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of flexible capacitive sensors, and in particular to a floating gate carbon nanotube transistor flexible pressure sensor based on an edge field and a preparation method thereof. Background Art

[0002] Flexible mechanical sensitive elements based on edge field effect usually use the edge field generated by the planar interdigitated electrodes on the flexible substrate and the elastic mechanical sensitive layer to detect the external pressure signal, and integrate it with the transistor electronic circuit to form a transistor flexible pressure sensor based on edge field, which can directly convert the pressure signal into the current or voltage change, which is conducive to the subsequent signal processing and its integration with complex electronic circuits and amplification of the output signal. Compared with other types of sensors, transistor pressure sensors based on edge field have the characteristics of low power consumption, compact device structure, high integration, small size, easy to expand into arrays, and easy signal processing and amplification. They are expected to be used in emerging fields such as neural prostheses, human-computer interaction, intelligent robots, and advanced health electronic medical care.

[0003] Existing flexible pressure sensor design schemes with integrated transistors: In terms of the design of flexible mechanical sensitive elements, there are a type of flexible pressure sensor that uses a vertical electrode structure and a microstructured elastomer dielectric layer in the middle of the electrode and a type of flexible mechanical sensitive element that uses a planar interdigitated electrode and a microstructured elastomer dielectric layer above it as a mechanical sensitive element. Since the microstructured elastomer dielectric layer is usually thicker and has a lower dielectric constant, the electrostatic control ability of the sensor using the above design scheme is relatively weak, and the sensing sensitivity is also relatively low. In addition, the mechanical sensitive element of the vertical electrode structure design scheme also has problems such as relatively poor mechanical stability of the device due to the serious mechanical mismatch between the wire and the elastomer and relatively difficult expansion into an array; in terms of transistor design and integration, organic semiconductor thin film transistors are usually used. Although they have mechanical compliance, their electrical properties are usually relatively poor, resulting in a relatively high operating voltage of the transistor. At the same time, the electrical properties of organic thin film transistor devices are unstable and are prone to further deterioration over time. In addition, since the existing transistor integration method is usually to directly laminate the mechanical sensitive element on the semiconductor film and its dielectric layer, the semiconductor film and its dielectric layer are easily damaged by external stress, which reduces the overall mechanical stability of the device. Summary of the invention

[0004] The present invention solves the problems of relatively low sensor sensitivity, relatively high operating voltage, relatively poor mechanical and electrical stability, and relatively difficult array expansion in existing transistor-integrated flexible pressure sensors due to relatively limited device structure and electrostatic control capabilities. The present invention provides a floating-gate carbon nanotube transistor flexible pressure sensor based on an edge field to solve the above problems.

[0005] The technical solution to be protected by the present invention is as follows:

[0006] A floating gate carbon nanotube transistor flexible pressure sensor based on edge field, comprising an elastomeric composite electrode, a layered composite dielectric layer, a forked electrode, a floating gate carbon nanotube transistor and a flexible substrate, characterized in that the elastomeric composite electrode is a composite of an elastomeric electrode and a metal electrode, the elastomeric electrode is an elastomer prepared from a composite material of polydimethylsiloxane and conductive carbon nanotubes, the elastomeric electrode forms a multi-scale microstructure on the outer surface facing the layered 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 layered composite dielectric layer is located between the outer surface of the elastomeric composite electrode with the multi-scale microstructure and the forked electrode. Between the electrodes, an organic dielectric and an inorganic metal oxide dielectric form an upper and lower layer structure composite; the interdigitated electrodes adopt a coplanar design, wherein one electrode is extended in the opposite direction of the non-extended electrode, and is extended to the outside of the elastomer composite electrode, serving as a floating gate electrode in a floating gate carbon nanotube transistor, and is used for the integration of the floating gate carbon nanotube transistor, wherein the transistor dielectric layer, channel, source electrode and drain electrode in the floating gate carbon nanotube transistor are located on the extended portion of the extended electrode outside the elastomer composite electrode; the upper surface of the interdigitated electrodes is connected to the inorganic metal oxide dielectric in the layered composite dielectric layer, and the lower surface is connected to hafnium oxide; the lower surface of the hafnium oxide is connected to a flexible substrate.

[0007] Preferably, the preparation method of the composite material of polydimethylsiloxane and conductive carbon nanotubes is: mixing polydimethylsiloxane with a n-hexane solution, dispersing the conductive 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 conductive carbon nanotubes to isopropyl alcohol is 1:200, and the ratio of the polydimethylsiloxane to the conductive 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 in the layered composite dielectric layer is made of polyxylene or polyimide, with a thickness of less than 200 nm, and the inorganic metal oxide dielectric in the layered composite dielectric layer and the transistor dielectric layer in the floating gate carbon nanotube transistor are made of aluminum oxide or yttrium oxide, with a thickness of 10-20 nm.

[0012] Preferably, the flexible substrate is made by depositing parylene or spin coating polyimide, and has a thickness of 1-3 μm.

[0013] The present invention also provides a method for preparing the above-mentioned floating gate carbon nanotube transistor flexible pressure sensor based on fringe field, the steps of which are as follows:

[0014] S1: thermally depositing polyparaxylene or spin-coating polyimide on a low-resistance silicon wafer to obtain an upper flexible substrate for reducing the adhesion of the elastomer electrode; using a mixed solution of polydimethylsiloxane and conductive carbon nanotubes to prepare an elastomer electrode; forming a multi-scale microstructure on the outer surface of the elastomer electrode facing the layered 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, wherein the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm, and the surface of the elastomer electrode without the multi-scale microstructure is connected to the flexible substrate, and finally obtaining an elastomer composite electrode composed of an elastomer electrode and a metal electrode;

[0015] S2: thermally depositing polyparaxylene or spin coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate having a length greater than the length of the elastomer composite electrode obtained in S1, obtaining hafnium oxide with a thickness of 5 nm on the flexible substrate by atomic layer deposition, which is used to increase the adhesion between the flexible substrate and the interdigitated electrodes, obtaining coplanar interdigitated electrodes on the surface of the hafnium oxide by electron beam or thermal evaporation, extending one of the electrodes in the opposite direction of the non-extended electrode to the outside of the elastomer composite electrode obtained in S1, and the extended electrode is used as a floating gate electrode in a floating gate carbon nanotube transistor for the integration of floating gate carbon nanotube transistors; obtaining an inorganic metal oxide with a thickness of 10-20 nm on the surface of the interdigitated electrodes by atomic layer deposition, the inorganic metal oxide on the surface of the non-extended electrode in the interdigitated electrode is the inorganic metal oxide dielectric in the layered composite dielectric layer, and the inorganic metal oxide on the surface of the extended electrode is the elastomer composite dielectric obtained in S1. The length of the elastomer composite electrode is used as the boundary, and it is divided into two parts by photolithography, wherein the left section close to the unextended electrode is located below the elastomer composite electrode and also serves as an inorganic metal oxide dielectric, and the remaining right section is located outside the elastomer composite electrode as a transistor dielectric layer in a floating gate carbon nanotube transistor; a high-purity semiconductor carbon nanotube film is obtained on the upper surface of the transistor dielectric layer by pulling and photolithography methods, that is, a channel is obtained; then a source electrode and a drain electrode are obtained at both ends of the channel by electron beam or thermal evaporation methods; finally, polyparaxylene or spin-coated polyimide is deposited on the surface of the inorganic metal oxide dielectric, and the polyparaxylene or polyimide located on the surface of the inorganic metal oxide dielectric serves as an organic dielectric, and together with the inorganic metal oxide dielectric, a layered composite dielectric layer is formed; finally, the silicon wafer at the bottom is peeled off, that is, a connected layered composite dielectric layer, an interdigitated electrode, a floating gate carbon nanotube transistor and a flexible substrate are obtained;

[0016] S3: Laminating the elastomer composite electrode obtained in S1 and the layered composite dielectric layer obtained in S2 to obtain a flexible pressure sensor with integrated floating gate carbon nanotube transistor.

[0017] Preferably, the forming of the multi-scale microstructure refers to drop-coating a mixed solution of polydimethylsiloxane and conductive carbon nanotubes onto a hydrophobic substrate, evacuating the substrate and then heating and curing the mixed solution, and irregular microstructures naturally appear on the surface of the mixed solution during the curing process; or etching a silicon wafer by photolithography to obtain a micro-pyramid structure mold of different sizes, after the mold is hydrophobicized, pouring the mixed solution of polydimethylsiloxane and conductive carbon nanotubes into the mold and evacuating the substrate, heating and curing the mold, and then peeling off the mold to obtain micro-pyramid structures of different sizes.

[0018] Preferably, the source electrode and the drain electrode in S2 are made of a metal alloy of titanium, palladium and gold by electron beam or thermal evaporation, the thickness of the titanium metal layer is 0.3 nm, the thickness of the palladium metal layer is 40 nm, and the thickness of the gold is 50 nm.

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

[0020] The present invention provides a floating gate carbon nanotube transistor flexible pressure sensor based on edge field, comprising an elastomer composite electrode, a layered composite dielectric layer, an interdigitated electrode, a floating gate carbon nanotube transistor and a flexible substrate, characterized in that the elastomer composite 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 conductive carbon nanotubes, the elastomer electrode forms a multi-scale microstructure on the outer surface facing the layered 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 layered composite dielectric layer is located on the outer surface of the elastomer composite electrode with the multi-scale microstructure Between the interdigital electrodes, an organic dielectric and an inorganic metal oxide dielectric form an upper and lower layer structure composite; the interdigital electrodes adopt a coplanar design, wherein one electrode is extended in the opposite direction of the non-extended electrode, and is extended to the outside of the elastomer composite electrode, serving as a floating gate electrode in a floating gate carbon nanotube transistor, and is used for the integration of floating gate carbon nanotube transistors, wherein the transistor dielectric layer, channel, source electrode and drain electrode in the floating gate carbon nanotube transistor are located on the extended portion of the extended electrode outside the elastomer composite electrode; the upper surface of the interdigital electrodes is connected to the inorganic metal oxide dielectric in the layered composite dielectric layer, and the lower surface is connected to hafnium oxide; the lower surface of the hafnium oxide is connected to a flexible substrate.

[0021] In terms of mechanical sensitive elements, the present invention adopts an elastomer composite electrode and a device configuration of a layered composite dielectric layer on a coplanar interdigitated electrode. On the one hand, the elastomer composite electrode can effectively localize the edge field to the composite dielectric layer in contact with the microstructure electrode, thereby greatly improving the regulation ability of the edge field, so that the sensor can significantly increase the change in the equivalent gate voltage of the transistor under the same gate voltage and external pressure, thereby greatly improving the change in the current between the source and drain electrodes, that is, greatly improving the sensitivity of the sensor and effectively reducing the operating voltage; on the other hand, the coplanar interdigitated electrode does not need to electrically connect the elastomer to the wire, which can reduce the mechanical instability caused by the mechanical mismatch between the elastomer and the wire. In addition, the coplanar interdigitated electrode design allows all electrical interfaces of the transistor integrated sensor to be designed through standard photolithography processes, which is conducive to the array expansion of the device. The multi-scale microstructure design can effectively avoid the problem of easy response saturation caused by the nonlinear characteristics of the material in the single microstructure design, thereby effectively improving the sensing range.

[0022] In terms of transistor design and integration, the use of a floating gate structure can effectively prevent mechanically sensitive elements from being directly laminated on semiconductor films and their dielectric layers, thereby preventing transistor damage and increasing the mechanical stability of the device. The use of high-purity semiconductor carbon nanotube materials with high mechanical and electrical properties can, on the one hand, utilize the high electrical properties of carbon nanotubes to effectively reduce the operating voltage of the device, and on the other hand, can utilize the characteristics of the carbon nanotube preparation method that can be matched with standard photolithography processes, which is conducive to device scaling and arraying. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Structural diagram of floating-gate carbon nanotube transistor flexible pressure sensor based on fringe field. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present invention clearer, the following is a further detailed description of the floating gate carbon nanotube transistor flexible pressure sensor based on edge field proposed by the present invention 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 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.

[0025] 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 based on a floating gate carbon nanotube transistor with an edge field, such as Figure 1 As shown, it includes: an elastomer composite electrode 1: an upper flexible substrate 11, an elastomer electrode 12 composed of a composite material, a multi-scale microstructure design 13 formed on the outer surface of the elastomer electrode facing the layered composite dielectric layer, a metal layer electrode 14 evaporated on the surface of the multi-scale microstructure, a layered composite dielectric layer 2: an organic dielectric 21, an inorganic metal oxide dielectric 22, coplanar designed interdigitated electrodes 311, 312, a carbon nanotube transistor 3: a floating gate electrode 312, a transistor dielectric layer 32, a channel 33, a source electrode 34, a drain electrode 35, and a flexible substrate 4: hafnium oxide 41, a flexible substrate 42.

[0026] In some embodiments of the present invention, a floating gate carbon nanotube transistor flexible pressure sensor based on an edge field comprises an elastomeric composite electrode 1, a layered composite dielectric layer 2, forked electrodes 311, 312 and a carbon nanotransistor 3, and a flexible substrate 4, characterized in that the elastomeric composite electrode 1 is composited by an elastomeric electrode 12 and a metal electrode 13, the elastomeric electrode 12 is an elastomer prepared from a composite material of polydimethylsiloxane and conductive carbon nanotubes, and the elastomeric electrode 12 forms a multi-scale microstructure 13 on the outer surface facing the layered composite dielectric layer 2; the metal electrode 14 is a metal layer electrode evaporated on the outer surface of the elastomeric electrode 12 having the multi-scale microstructure 13; the layered composite dielectric layer 2 is located between the outer surface of the elastomeric composite electrode 1 having the multi-scale microstructure 13 and the forked electrodes 311, 312. The interdigitated electrodes 311 and 312 are composited by an organic dielectric 21 and an inorganic metal oxide dielectric 22 to form an upper and lower layer structure; the interdigitated electrodes 311 and 312 are coplanarly designed, wherein one electrode 312 is extended in the opposite direction of the non-extended electrode 311, and is extended to the outside of the elastomer composite electrode 1, serving as a floating gate electrode in a floating gate carbon nanotube transistor 3, and is used for the integration of the floating gate carbon nanotube transistor 3, wherein the transistor dielectric layer 32, the channel 33, the source electrode 34 and the drain electrode 345 in the floating gate carbon nanotube transistor 3 are located on the surface of the extended portion of the extended electrode 312 located outside the elastomer composite electrode 1; the upper surfaces of the interdigitated electrodes 311 and 312 are connected to the inorganic metal oxide dielectric 22 in the layered composite dielectric layer 2, and the lower surfaces are connected to the hafnium oxide 41; the lower surface of the hafnium oxide 41 is connected to the flexible substrate 42.

[0027] In some embodiments of the present invention, the preparation method of the polydimethylsiloxane and conductive carbon nanotube composite material for preparing the elastomeric electrode 12 is: mixing polydimethylsiloxane with a n-hexane solution, dispersing the conductive carbon nanotubes in isopropanol by water bath ultrasound, and finally mixing the two solutions; in some embodiments of the present invention, the ratio of polydimethylsiloxane to n-hexane solution is 1:5-1:10, the ratio of conductive carbon nanotubes to isopropanol is 1:200, and the ratio of polydimethylsiloxane to conductive carbon nanotubes is 100:1-100:5.

[0028] In some embodiments of the present invention, the multi-scale microstructure 14 is a plurality of irregular three-dimensional structures; in other embodiments of the present invention, the multi-scale microstructure 14 is a plurality of micro-pyramid structures of different sizes.

[0029] In some embodiments of the present invention, the metal electrode 14 in the elastomer composite electrode 1 is obtained by electron beam evaporation of titanium-gold alloy, and the thickness of titanium is 5nm, and the thickness of gold is 50nm; in other embodiments of the present invention, the metal electrode 14 in the elastomer composite electrode 1 is obtained by thermal evaporation of titanium-gold alloy, and the thickness of titanium is 5nm, and the thickness of gold is 50nm; in some embodiments of the present invention, the metal electrode 14 in the elastomer composite electrode 1 is obtained by electron beam evaporation of chromium-gold alloy, and the thickness of chromium is 5nm, and the thickness of gold is 50nm; in other embodiments of the present invention, the metal electrode 14 in the elastomer composite electrode 1 is obtained by thermal evaporation of chromium-gold alloy, and the thickness of chromium is 5nm, and the thickness of gold is 50nm.

[0030] In some embodiments of the present invention, the interdigitated electrodes 311, 312 are obtained by electron beam evaporation of titanium-gold alloy, the thickness of titanium is 5nm, and the thickness of gold is 25nm; in other embodiments of the present invention, the interdigitated electrodes 311, 312 are obtained by electron beam evaporation of chromium-gold alloy, the thickness of chromium is 5nm, and the thickness of gold is 25nm; in some embodiments of the present invention, the interdigitated electrodes 311, 312 are obtained by superheated evaporation of titanium-gold alloy, the thickness of titanium is 5nm, and the thickness of gold is 30nm; in other embodiments of the present invention, the interdigitated electrodes 311, 312 are obtained by superheated evaporation of chromium-gold alloy, the thickness of chromium is 5nm, and the thickness of gold is 30nm.

[0031] In some embodiments of the present invention, the organic dielectric 21 in the layered composite dielectric layer 2 is polyparaxylene with a thickness of 150 nm, and the inorganic metal oxide dielectric 22 in the layered composite dielectric layer 2 and the transistor dielectric layer 32 in the floating gate carbon nanotube transistor are aluminum oxide with a thickness of 10 nm; in other embodiments of the present invention, the organic dielectric 21 in the layered composite dielectric layer 2 is polyimide with a thickness of 180 nm, and the inorganic metal oxide dielectric 22 in the layered composite dielectric layer 2 and the transistor dielectric layer 32 in the floating gate carbon nanotube transistor are yttrium oxide with a thickness of 20 nm.

[0032] In some embodiments of the present invention, the flexible substrate 42 is made of polyparaxylene by a deposition method, and has a thickness of about 1 μm; in some embodiments of the present invention, the flexible substrate 42 is made of polyimide by spin coating, and has a thickness of about 3 μm.

[0033] In some embodiments of the present invention, the method for preparing the floating gate carbon nanotube transistor flexible pressure sensor based on fringe field 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 for reducing the adhesion of the elastomer electrode; using a mixed solution of polydimethylsiloxane and conductive carbon nanotubes to prepare an elastomer electrode 12; forming a multi-scale microstructure 13 on the outer surface of the elastomer electrode 12 facing the layered composite dielectric layer 2, and obtaining a lower metal layer electrode 14 by electron beam or thermal evaporation of titanium-gold alloy or chromium-gold alloy on the outer surface of the elastomer electrode 12 having the multi-scale microstructure 13, wherein the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm, and the surface of the elastomer electrode 12 not having the multi-scale microstructure 13 is connected to the upper flexible substrate 11, so as to obtain an elastomer composite electrode 1 composed of the elastomer electrode 12 and the metal electrode 14;

[0035] S2: Thermally depositing polyparaxylene or spin coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate 42 having a length greater than the length of the elastomer composite electrode 1 obtained in S1, and obtaining hafnium oxide 41 with a thickness of 5 nm on the flexible substrate 42 by atomic layer deposition to increase the adhesion between the flexible substrate 42 and the interdigital electrodes 311 and 312, and obtaining coplanar interdigital electrodes 311 and 312 on the surface of the hafnium oxide 42 by electron beam or thermal evaporation, and connecting one of the electrodes 312 to the opposite side of the non-extended electrode 311. The extended electrode 312 is used as a floating gate electrode in the floating gate carbon nanotube transistor 3 and is used for the integration of the floating gate carbon nanotube transistor 3; an inorganic metal oxide with a thickness of 10-20 nm is obtained on the surface of the interdigitated electrodes 311 and 312 by atomic layer deposition, and the inorganic metal oxide on the surface of the electrode 311 that is not extended in the interdigitated electrode is the inorganic metal oxide dielectric 22 in the layered composite dielectric layer 2, and the inorganic metal on the surface of the extended electrode 312 is The oxide is divided into two parts by photolithography with the length of the elastomer composite electrode 1 as the boundary, wherein the left section close to the non-extended electrode 311 is located below the elastomer composite electrode 1 and also serves as the inorganic metal oxide dielectric 22, and the remaining right section is located outside the elastomer composite electrode 1 as the transistor dielectric layer 32 in the floating gate carbon nanotube transistor 3; a high-purity semiconductor carbon nanotube film is obtained on the upper surface of the transistor dielectric layer 32 by pulling and photolithography methods, that is, a channel 33 is obtained; and then electron beams are formed at both ends of the channel. or thermal evaporation method to obtain the source electrode 34 and the drain electrode 35; finally, polyparaxylene is deposited or polyimide is spin-coated on the inorganic metal oxide dielectric 22, and the polyparaxylene or polyimide on the surface of the inorganic metal oxide dielectric 22 is used as the organic dielectric 21, and together with the inorganic metal oxide dielectric 22, a layered composite dielectric layer 2 is formed; finally, the silicon wafer at the bottom is peeled off to obtain a connected layered composite dielectric layer 2, interdigitated electrodes 311, 312, a floating gate carbon nanotube transistor 3 and a flexible substrate 42;

[0036] S3: The elastomeric composite electrode 1 obtained in S1 is laminated with the layered composite dielectric layer 2, the interdigitated electrodes 311, 112, the floating gate carbon nanotube transistor 3 and the flexible substrate 4 which are connected in sequence from top to bottom obtained in S2, so that the elastomeric composite electrode 1 is connected to the organic dielectric layer 21 in the layered composite dielectric layer 2, thereby obtaining a flexible pressure sensor with an integrated floating gate carbon nanotube transistor.

[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 conductive 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 conductive 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 source electrode 34 and the drain electrode 35 are made of titanium, palladium and gold alloy by electron beam evaporation, the thickness of the titanium metal layer is 0.3nm, the thickness of the palladium metal layer is 40nm, and the thickness of the gold is 50nm; in other embodiments of the present invention, the source electrode 34 and the drain electrode 35 are made of titanium, palladium and gold alloy by thermal evaporation, the thickness of the titanium metal layer is 0.3nm, the thickness of the palladium metal layer is 40nm, and the thickness of the gold is 50nm.

[0039] The floating gate carbon nanotube transistor flexible pressure sensor based on edge field provided by the present invention can connect the gate voltage to the non-extended electrode 311 in the interdigitated electrode, connect the source voltage to the source electrode 34, and connect the drain voltage to the drain electrode 35 when in use.

[0040] 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.

[0041] 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 floating gate carbon nanotube transistor flexible pressure sensor based on edge field, comprising an elastomer composite electrode, a layered composite dielectric layer, an interdigitated electrode, a floating gate carbon nanotube transistor and a flexible substrate, characterized in that: The elastomer composite 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 conductive carbon nanotubes. The elastomer electrode forms a multi-scale microstructure on the outer surface facing the layered composite dielectric layer. The metal electrode is a metal layer electrode evaporated on the outer surface of the elastomer electrode with a multi-scale microstructure. The layered composite dielectric layer is located between the outer surface of the elastomer composite electrode with a multi-scale microstructure and the interdigitated electrode, and is composed of an upper and lower layer structure formed by an organic dielectric and an inorganic metal oxide dielectric. The interdigitated electrodes adopt a coplanar design, wherein one electrode is extended in the opposite direction of the non-extended electrode and extended to the outside of the elastomer composite electrode, serving as a floating gate electrode in a floating gate carbon nanotube transistor and used for the integration of the floating gate carbon nanotube transistor, wherein the transistor dielectric layer, channel, source electrode and drain electrode in the floating gate carbon nanotube transistor are located on the extended portion of the extended electrode outside the elastomer composite electrode; the upper surface of the interdigitated electrodes is connected to the inorganic metal oxide dielectric in the layered composite dielectric layer, and the lower surface is connected to hafnium oxide; the lower surface of the hafnium oxide is connected to a flexible substrate.

2. The floating gate carbon nanotube transistor flexible pressure sensor based on edge field according to claim 1, characterized in that: The preparation method of the polydimethylsiloxane and conductive carbon nanotube composite material is as follows: polydimethylsiloxane is mixed with a normal hexane solution, the conductive carbon nanotubes are dispersed in isopropanol by water bath ultrasound, and finally the two mixed solutions are mixed.

3. The floating gate carbon nanotube transistor flexible pressure sensor based on edge field 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 conductive carbon nanotubes to the isopropyl alcohol is 1:200, and the ratio of the polydimethylsiloxane to the conductive carbon nanotubes is 100:1-100:

5.

4. The floating gate carbon nanotube transistor flexible pressure sensor based on fringe field 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 floating gate carbon nanotube transistor flexible pressure sensor based on fringe field 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 floating gate carbon nanotube transistor flexible pressure sensor based on fringe field according to claim 1, characterized in that: The organic dielectric in the layered composite dielectric layer is made of polyxylene or polyimide, with a thickness of less than 200nm, and the inorganic metal oxide dielectric in the layered composite dielectric layer and the transistor dielectric layer in the floating gate carbon nanotube transistor are made of aluminum oxide or yttrium oxide, with a thickness of 10-20nm.

7. The floating gate carbon nanotube transistor flexible pressure sensor based on fringe field according to claim 1, characterized in that: The flexible substrate is made by depositing polyparaxylene or spin coating polyimide, and has a thickness of 1-3 μm.

8. A method for preparing a floating gate carbon nanotube transistor flexible pressure sensor based on fringe field 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 an upper flexible substrate for reducing the adhesion of the elastomer electrode; using a mixed solution of polydimethylsiloxane and conductive carbon nanotubes to prepare an elastomer electrode; forming a multi-scale microstructure on the outer surface of the elastomer electrode facing the layered 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, wherein the thickness of the titanium or chromium is 5nm, and the thickness of the gold is 50nm, and the surface of the elastomer electrode without the multi-scale microstructure is connected to the flexible substrate, and finally obtaining an elastomer composite electrode composed of an elastomer electrode and a metal electrode; S2: thermally depositing polyparaxylene or spin coating polyimide on a low-resistance silicon wafer to obtain a flexible substrate having a length greater than the length of the elastomer composite electrode obtained in S1, obtaining hafnium oxide with a thickness of 5 nm on the flexible substrate by atomic layer deposition, which is used to increase the adhesion between the flexible substrate and the interdigitated electrodes, obtaining coplanar interdigitated electrodes on the surface of the hafnium oxide by electron beam or thermal evaporation, extending one of the electrodes in the opposite direction of the non-extended electrode to the outside of the elastomer composite electrode obtained in S1, and the extended electrode is used as a floating gate electrode in a floating gate carbon nanotube transistor for the integration of floating gate carbon nanotube transistors; obtaining an inorganic metal oxide with a thickness of 10-20 nm on the surface of the interdigitated electrodes by atomic layer deposition, the inorganic metal oxide on the surface of the non-extended electrode in the interdigitated electrode is the inorganic metal oxide dielectric in the layered composite dielectric layer, and the inorganic metal oxide on the surface of the extended electrode is the elastomer composite dielectric obtained in S1. The length of the elastomer composite electrode is used as the boundary, and it is divided into two parts by photolithography, wherein the left section close to the non-extended electrode is located below the elastomer composite electrode and also serves as an inorganic metal oxide dielectric, and the remaining right section is located outside the elastomer composite electrode as a transistor dielectric layer in a floating gate carbon nanotube transistor; a high-purity semiconductor carbon nanotube film is obtained on the upper surface of the transistor dielectric layer by pulling and photolithography methods, that is, a channel is obtained; then a source electrode and a drain electrode are obtained at both ends of the channel by electron beam or thermal evaporation methods; finally, polyparaxylene or spin-coated polyimide is deposited on the surface of the inorganic metal oxide dielectric, and the polyparaxylene or polyimide located on the surface of the inorganic metal oxide dielectric serves as an organic dielectric, and together with the inorganic metal oxide dielectric, a layered composite dielectric layer is formed; finally, the silicon wafer at the bottom is peeled off, that is, a connected layered composite dielectric layer, an interdigitated electrode, a floating gate carbon nanotube transistor and a flexible substrate are obtained; S3: Laminating the elastomer composite electrode obtained in S1 and the layered composite dielectric layer obtained in S2 to obtain a flexible pressure sensor with integrated floating gate carbon nanotube transistor.

9. The preparation method according to claim 8, characterized in that: The forming of the multi-scale microstructure refers to drop-coating a mixed solution of polydimethylsiloxane and conductive carbon nanotubes onto a hydrophobic substrate, evacuating the substrate and then heating and curing the mixed solution, and irregular microstructures naturally appear on the surface of the mixed solution during the curing process; or etching a silicon wafer by photolithography to obtain a micro-pyramid structure mold of different sizes, after the mold is hydrophobicized, pouring the mixed solution of polydimethylsiloxane and conductive carbon nanotubes into the mold and evacuating the substrate, heating and curing the mold, and then peeling off the mold to obtain micro-pyramid structures of different sizes.

10. The preparation method according to claim 8 or 9, characterized in that: The source electrode and drain electrode in S2 are made of titanium, palladium and gold metal alloys by electron beam or thermal evaporation. The thickness of the titanium metal layer is 0.3nm, the thickness of the palladium metal layer is 40nm, and the thickness of the gold is 50nm.

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