Floating-gate carbon nanotube transistor flexible pressure sensor based on fringe field and preparation method thereof

Abstract

The present invention provides a floating-gate carbon nanotube transistor flexible pressure sensor based on fringe fields, comprising an elastomer composite electrode, a layered composite dielectric layer, interdigitated electrodes, 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 made of a PDMS and CNT composite material, and its outer surface forms a multi-scale microstructure. The metal electrode is evaporated on the outer surface of the multi-scale microstructure. The layered composite dielectric layer comprises an organic dielectric and an inorganic dielectric. The interdigitated electrodes are coplanar in design, with one electrode extending beyond the elastomer composite electrode in the opposite direction of the non-extended electrode to serve as a floating gate electrode. The transistor dielectric layer, channel, and source / drain electrodes are located on the extended portion of the delay electrode outside the elastomer composite electrode. The present invention enhances the ability to control fringe fields, significantly improves the sensitivity and mechanical stability of the sensor, reduces the operating voltage, and facilitates array expansion.

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 fringe fields and a preparation method thereof. Background Art

[0002] Flexible mechanical sensors based on the fringe field effect typically utilize the fringe field generated by planar interdigitated electrodes on a flexible substrate and an elastomeric mechanically sensitive layer to detect external pressure signals. These sensors are then integrated with transistor electronic circuits to form a fringe field-based transistor flexible pressure sensor. These sensors can directly convert pressure signals into current or voltage changes, facilitating subsequent signal processing, integration with complex electronic circuits, and amplification of the output signal. Compared to other types of sensors, fringe field-based transistor pressure sensors offer low power consumption, compact device structure, high integration, small size, ease of expansion into arrays, and convenient signal processing and amplification. They are expected to be applied in emerging fields such as neural prosthetics, human-computer interaction, intelligent robotics, and advanced healthcare electronics.

[0003] Existing designs for flexible pressure sensors with integrated transistors: Regarding the design of flexible mechanical sensors, there are two approaches: one employing a vertical electrode structure with a microstructured elastomeric dielectric layer between the electrodes and another employing a planar interdigitated electrode with a microstructured elastomeric dielectric layer above it as the mechanical sensor. Because microstructured elastomeric dielectric layers are typically thick and have a low dielectric constant, sensors using these designs have relatively weak electrostatic control capabilities and low sensing sensitivity. Furthermore, mechanical sensors with vertical electrode structures suffer from poor mechanical stability due to the severe mechanical mismatch between the wires and the elastomer, as well as difficulty in expanding into arrays. Regarding transistor design and integration, organic semiconductor thin-film transistors are commonly used. While they offer mechanical compliance, their electrical performance is generally poor, resulting in relatively high operating voltages. Furthermore, the electrical performance of organic thin-film transistors is unstable and prone to degradation over time. Furthermore, because existing transistor integration methods typically laminate the mechanical sensor directly onto the semiconductor film and its dielectric layer, the semiconductor film and dielectric layer are susceptible to damage from external stress, reducing the overall mechanical stability of the device. Summary of the Invention

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

[0005] The technical solutions to be protected by the present invention are as follows:

[0006] A floating-gate carbon nanotube transistor flexible pressure sensor based on an 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 a composite of 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 between the outer surface of the elastomer composite electrode with the multi-scale microstructure and the interdigitated 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, extending 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 interdigitated electrode 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 the flexible substrate.

[0007] Preferably, the preparation method of the polydimethylsiloxane and conductive carbon nanotube composite material is: mixing polydimethylsiloxane with n-hexane solution, dispersing the conductive carbon nanotubes in isopropyl alcohol 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 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 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, comprising the following steps:

[0014] S1: thermally depositing parylene 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 the 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 5 nm and the thickness of the gold is 50 nm; the surface of the elastomer electrode not having the multi-scale microstructure is connected to the flexible substrate, and finally obtaining an elastomer composite electrode composed of the elastomer electrode and the metal electrode;

[0015] S2: Thermally depositing parylene 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 to increase the adhesion between the flexible substrate and the interdigitated electrodes, obtaining coplanar interdigitated electrodes on the hafnium oxide surface 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, the extended electrode serving as the floating gate electrode in a floating gate carbon nanotube transistor for the integration of the floating gate carbon nanotube transistor; 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 being the inorganic metal oxide dielectric in the layered composite dielectric layer, and the inorganic metal oxide on the surface of the extended electrode being the elastomer composite electrode obtained in S1. The length of the elastomer composite electrode is used as the boundary and 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 and serves as the transistor dielectric layer in the 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, parylene or spin-coated polyimide is deposited on the surface of the inorganic metal oxide dielectric, and the parylene or polyimide located on the surface of the inorganic metal oxide dielectric serves as an organic dielectric and constitutes a layered composite dielectric layer together with the inorganic metal oxide dielectric; finally, the bottom silicon wafer is peeled off to obtain a connected layered composite dielectric layer, interdigitated electrodes, floating gate carbon nanotube transistor and flexible substrate;

[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 transistors.

[0017] Preferably, the forming of the multi-scale microstructure comprises 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, wherein 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 mold with micro-pyramid structures of different sizes, treating the mold hydrophobically, pouring the mixed solution of polydimethylsiloxane and conductive carbon nanotubes into the mold, evacuating the substrate, heating and curing the mixed solution, and then peeling off the mold to obtain micro-pyramid structures of different sizes.

[0018] Preferably, the source electrode and 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 an 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 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, in which one electrode is extended in the opposite direction of the non-extended electrode, extending 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 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 electrode 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 the 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 constructed 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 control 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, significantly improving the sensitivity of the sensor and effectively reducing the operating voltage; on the other hand, the coplanar interdigitated electrodes do not need to electrically connect the elastomer to the wire, which can reduce the mechanical instability problem 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 the semiconductor film and its dielectric layer, prevent transistor damage, and increase 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, utilize the characteristics of carbon nanotube preparation methods 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 a flexible pressure sensor based on fringe field and floating-gate carbon nanotube transistors. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions 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 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 structures, proportions, sizes, 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 significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0025] 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 based on a floating gate carbon nanotube transistor with an edge field. 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, 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 includes an elastomer composite electrode 1, a layered composite dielectric layer 2, interdigitated electrodes 311, 312 and a carbon nanotransistor 3, and a flexible substrate 4, characterized in that the elastomer composite 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 conductive carbon nanotubes, and the elastomer 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 elastomer electrode 12 having the multi-scale microstructure 13; the layered composite dielectric layer 2 is located between the outer surface of the elastomer composite electrode 1 having the multi-scale microstructure 13 and the interdigitated electrodes 311, 312. The interdigitated electrodes 311 and 312 are coplanar in design, wherein one electrode 312 is extended in the opposite direction of the non-extended electrode 311 and extends beyond the elastomer composite electrode 1 to serve as a floating gate electrode in the floating gate carbon nanotube transistor 3 for integration of the floating gate carbon nanotube transistor 3. The transistor dielectric layer 32, channel 33, source electrode 34 and 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 isopropyl alcohol by water bath ultrasound, and finally mixing the two solutions; in some embodiments of the present invention, 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.

[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 the titanium is 5 nm, and the thickness of the gold is 50 nm; 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 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 in the elastomer composite electrode 1 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 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 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 311 and 312 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 311 and 312 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 311 and 312 are obtained by superheated 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 311 and 312 are obtained by superheated 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 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 deposition, with a thickness of about 1 μm; in some embodiments of the present invention, the flexible substrate 42 is made of polyimide by spin coating, with a thickness of about 3 μm.

[0033] In some embodiments of the present invention, the method for preparing the fringe field-based floating-gate carbon nanotube transistor flexible pressure sensor 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 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 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 to obtain a lower metal layer electrode 14, wherein the thickness of the titanium or chromium is 5 nm and the thickness of the gold is 50 nm, and the surface of the elastomer electrode 12 not having the multi-scale microstructure 13 is connected to the upper flexible substrate 11, thereby obtaining an elastomer composite electrode 1 composed of the elastomer electrode 12 and the metal electrode 14;

[0035] S2: Thermally depositing parylene 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 depositing 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, 312, and obtaining coplanar interdigital electrodes 311, 312 on the surface of the hafnium oxide 42 by electron beam or thermal evaporation, and placing one of the electrodes 312 on the opposite side of the non-extended electrode 311. The extended electrode 312 is extended to the outside of the elastomer composite electrode 1 obtained in S1, and the extended electrode 312 is used as the floating gate electrode in the floating gate carbon nanotube transistor 3 for the integration of the floating gate carbon nanotube transistor 3; an inorganic metal oxide with a thickness of 10-20 nm is obtained by atomic layer deposition on the surface of the interdigitated electrodes 311 and 312, and the inorganic metal oxide on the surface of the non-extended electrode 311 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 and serves 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 used at both ends of the channel. or thermal evaporation method to obtain the source electrode 34 and the drain electrode 35; finally, depositing parylene or spin-coating polyimide on the inorganic metal oxide dielectric 22; the parylene or polyimide located on the surface of the inorganic metal oxide dielectric 22 serves as the organic dielectric 21, and together with the inorganic metal oxide dielectric 22, constitutes the layered composite dielectric layer 2; finally, peeling off the bottom silicon wafer, thus obtaining the connected layered composite dielectric layer 2, the interdigitated electrodes 311, 312, the floating gate carbon nanotube transistor 3 and the flexible substrate 42;

[0036] S3: The elastomer 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 connected in sequence from top to bottom obtained in S2, so that the elastomer 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 is to drop-coat a mixed solution of polydimethylsiloxane and conductive 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 conductive carbon nanotubes is poured into the mold and evacuated. After heating and solidification, the mold is peeled off 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, and 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; 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, and 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.

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

[0040] 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.

[0041] 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 floating-gate carbon nanotube transistor flexible pressure sensor based on fringe fields, comprising an elastomer composite electrode, a layered composite dielectric layer, interdigitated electrodes, 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 the multi-scale microstructure. The layered composite dielectric layer is located between the outer surface of the elastomer composite electrode with the 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 extends beyond the elastomer composite electrode to serve 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. 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 the flexible substrate.

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

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

8. A method for preparing a fringe field-based floating-gate carbon nanotube transistor flexible pressure sensor 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 an upper flexible substrate for reducing the adhesion of the elastomer electrode; using a mixed solution of polydimethylsiloxane and conductive carbon nanotubes to prepare the 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 5 nm and the thickness of the gold is 50 nm; the surface of the elastomer electrode not having the multi-scale microstructure is connected to the flexible substrate, and finally obtaining an elastomer composite electrode composed of the elastomer electrode and the metal electrode; S2: Thermally depositing parylene 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 to increase the adhesion between the flexible substrate and the interdigitated electrodes, obtaining coplanar interdigitated electrodes on the hafnium oxide surface 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, the extended electrode serving as the floating gate electrode in a floating gate carbon nanotube transistor for the integration of the floating gate carbon nanotube transistor; 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 being the inorganic metal oxide dielectric in the layered composite dielectric layer, and the inorganic metal oxide on the surface of the extended electrode being the elastomer composite electrode obtained in S1. The length of the elastomer composite electrode is used as the boundary and 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 and serves as the transistor dielectric layer in the 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 bottom silicon wafer is peeled off to obtain a connected layered composite dielectric layer, interdigitated electrodes, floating gate carbon nanotube transistor and flexible substrate; 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 transistors.

9. The preparation method according to claim 8, characterized in that The multi-scale microstructure formation method comprises the following steps: 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. During the curing process, irregular microstructures naturally appear on the surface of the mixed solution. Alternatively, a silicon wafer is etched by photolithography to obtain a mold with micro-pyramid structures of different sizes. After the mold is hydrophobicized, the mixed solution of polydimethylsiloxane and conductive 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 preparation method according to claim 8 or 9, characterized in that: The source electrode and 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.

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