Three-dimensional carbon nano-material field effect flexible force sensing element and preparation method

A carbon nanomaterial and sensing element technology, applied in the field of electronic information, can solve the problems of environmental noise suppression, low signal-to-noise ratio, uncertainty of quantitative load measurement, etc., and achieve the effect of high sensitivity

Active Publication Date: 2017-06-13

SOUTHEAST UNIV

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AI-Extracted Technical Summary

Problems solved by technology

At present, the practical flexible force-sensitive sensing element is basically a piezoelectric polymer material polyvinylidene fluoride (PVDF) film. Due to the weak signal of this type of force-sensitive element, the signal needs to be pre-ampli...

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Method used

Above-mentioned structure measurement signal is the electric current of microampere to milliampere level or adopts sampling resistance to obtain millivolt level voltage signal, because graphene has lower temperature conductance coefficient, adopts the force sensitive sensing element of graphene without Temp...

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Abstract

The invention relates to a design and preparation method for a flexible force sensing element based on a continuous three-dimensional graphene or carbon nanotube field effect structure. Field effect conductivity changes under constant grid voltage of graphene or carbon nanotubes covering the surface of an elastomer pyramid strip are used by the sensing element, a grid electrode is design to be a plane flexible electrode covering the graphene or the carbon nanotube pyramid strip or the top end of an array, the area of a source leakage channel is increased under the compressive deformation for a pyramid by the grid electrode, the field effect conductivity is increased, and the element is high in deformation or loading flexibility. By the designation of the width of the strip, the density of the array and the elasticity modulus of base elastomer materials, force sensing elements with different flexibilities in the loading measurement range of 0-3 MPa can be obtained, and a force sensing film of which the transparency is higher than 80% and the bending curvature is less than 3 mm can be designed and prepared.

Application Domain

Fluid pressure measurement using piezo-electric devicesGraphene +3

Technology Topic

Carbon nanotubePyramid +8

Image

Examples

Experimental program(3)

Example Embodiment

[0055] The method for preparing the three-dimensional structure of the copper surface firstly uses the template method to prepare the three-dimensional structure of the thermoplastic polyurethane, and the steps are:

[0056] (1) Firstly, single or multiple strip-shaped windows are etched on the surface of the silicon wafer with oxide layer, then the oxide layer is removed by HF etching, and then the tetramethylammonium hydroxide aqueous solution is added with isopropanol to etch the pyramid Strip corrosion pit negative type;

[0057] (2) Fill the heated pyramid-shaped silicon negative type with molten thermoplastic polyurethane, and mechanically peel it off after curing under vacuum to form a positive type polyurethane film;

[0058] (3) Coat a layer of polymethyl methacrylate on the positive surface of the above-mentioned polyurethane by the glue spin method with a thickness of less than 1 micron. After it is fully dried, a layer of pure copper is evaporated on the surface by the vacuum evaporation method to cover the surface with The glue film of the copper film is suspended in the copper sulfate electrolyte, with pure copper as the anode, the positive type of the above glue film is the cathode, and a layer of pure copper is slowly deposited on the surface;

[0059] (4) The deposited copper film is cleaned, dried, and then immersed in toluene for 1 minute, taken out and dried, and the adhesive film is positively peeled off. After the copper film is soaked in chloroform for 10 hours, it is taken out and dried and stored in a dry pure nitrogen environment.

[0060] The chemical vapor phase method for depositing graphene on the surface of the copper structure is to anneal the copper structure in hydrogen at 700°C for 1 hour, then discharge the hydrogen, raise the temperature to 900-1020°C, keep it for 1 hour, and then press the 1:1 flow rate Pass in methane and hydrogen, keep it at 900~1020°C for 15 minutes, and then slowly lower the temperature to obtain single or multilayer graphene grown on the copper surface.

[0061] The surface of the copper structure is filled with an elastomer material to form a continuous substrate thick film, and the elastomer is any one of room temperature curing silicone rubber, thermoplastic polyurethane, and ether ester type thermoplastic elastomer;

[0062] The aqueous solution dissolves the copper film, and the aqueous solution is a saturated solution of ferric chloride and ferric nitrate solution.

[0063] In the preparation of the field effect measurement area on the surface of graphene or carbon nanotubes, the pyramid strips are first covered by photolithography with aqueous photoresist, and then oxygen plasma is used to remove the exposed part of the graphene or carbon nanotubes, and then use The ink-jet printing method is used to prepare silver or copper nanowire electrodes on pyramid strips or strip arrays. The electrode line width is 40 to 150 microns. The density of the nanowire electrodes is maintained at a sheet resistance not higher than 200 ohms, and the electrodes are attached to graphite Source and drain electrodes on the surface of alkene or carbon nanotubes.

[0064] Said depositing a layer of 1-ethyl-3-methylimidazole bistrifluoromethanesulfonimide salt ionic liquid and vinylidene fluoride-hexafluoropropylene copolymer ion colloidal dielectric film on the surface of graphene, using a solution The gel spin method is deposited on the surface of graphene or carbon nanotubes, and the thickness is not greater than 200 nanometers.

[0065] In the conductive grid, the matrix is any one of thermoplastic polyurethane and ether ester type thermoplastic elastomer, and the covered flexible conductive material is carbon nanotube, silver nanowire, copper nanowire, and its density makes the square resistance less Greater than 1000 ohms.

Example Embodiment

[0066] Example one

[0067] 1. Using photolithography, the oxide layer thickness is 500 nm, and the crystal orientation is <100> Single or multiple parallel photoresist windows with a width of 20 microns to 150 microns and a length of 150 microns to 500 microns are prepared on the monocrystalline silicon wafer. Hydrofluoric acid is used to dissolve the oxide layer at the window, and then placed in a 1:1 25 In a mixed solution of tetramethylammonium hydroxide aqueous solution and isopropanol with a weight ratio of 5%, etch at 95°C, take it out when the cone-shaped tip is fully formed, wash and dry to obtain a negative silicon pyramid;

[0068] 2. Cover the negative surface of the silicon pyramid with a thermoplastic polyurethane sheet with a thickness of 2 mm, heat it to 165°C in a vacuum, hold it under pressure for 5 minutes, take it out, and peel off the polyurethane adhesive layer after cooling and solidification to obtain a positive polyurethane elastomer film ;

[0069] 3. First, the positive type of the film is soaked in a polymethyl methacrylate chlorobenzene solution with a molecular weight of 996K and a concentration of about 6% by weight, and then take it out and dry it at 150°C for 5 minutes, and then evaporate it on its surface by vacuum evaporation. Layer of pure copper with a thickness of more than 100 nanometers, and then bond the electrode wires with conductive glue on the surface, dry and fix it, put it in a bright copper electroplating solution, take the positive type of the glue film as the cathode, and the pure copper sheet as the positive electrode. Deposit a layer of pure copper on the surface of the silicone rubber with a thickness of not less than 1 mm;

[0070] 4. After cleaning and drying the deposited copper film with pure water, put it in toluene and let it stand for 1 minute. The film is positively peeled off and dried to obtain a copper negative film. Step 3 can be repeated for the film to prepare another A copper negative type;

[0071] 5. Soak the stripped copper negative type in chloroform for 10 hours, take it out and dry it, and put it in a pure nitrogen environment for storage;

[0072] 6. Use chemical vapor deposition to deposit graphene on the copper negative surface. The steps are: annealing the copper negative in 0.6Pa hydrogen at 700°C for 1 hour, then exhaust the hydrogen, heat it up to 900-1020°C, and keep it for 1 hour. Then pass in methane and hydrogen at a flow rate of 1:1, keep it at 900~1020°C for 15 minutes, and then slowly lower the temperature to obtain single or multilayer graphene grown on the copper surface.

[0073] 7. Add the room temperature curing silicone rubber liquid mixed with the curing agent dropwise on the copper negative surface where graphene is grown. After degassing in a vacuum for 5 minutes, keep it at room temperature for 24 hours. After the silicone rubber is fully cured, Put the copper negative type filled with silicone rubber in a saturated aqueous solution of ferric nitrate for 24 hours. When the copper is fully dissolved, take out the silicone rubber, wash and dry it, and obtain a positive type silicone rubber covered with continuous graphene;

[0074] 8. Prepare the photoresist pattern covering the pyramid measurement area by photolithography, then use oxygen plasma to remove the graphene in the exposed area, and then use inkjet printing to prepare strip source and drain electrodes on the pyramid surface covered with graphene , The 0.5mg/ml concentration of copper nanowire ethanol/ethylene glycol suspension was printed with an inkjet printer in the vertical pyramid strip direction to print continuous parallel electrodes with a density such that the sheet resistance was not greater than 200 ohms, and the conductive nanowires were obtained as electrodes The source and drain electrodes of the field effect, lead the source and drain electrodes out of the wire;

[0075] 9. A mixture of 10% by weight of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl) ionic liquid and vinylidene fluoride-hexafluoropropylene copolymer (weight ratio 1:2) ionic colloid The dimethylformamide solution is used to coat the graphene and electrode surface by the spin-off method, and dried at 150°C for 1 hour to form an ion colloidal dielectric film with a thickness of not more than 200 nanometers;

[0076] 10. Use a spray method to coat copper nanowires on the surface of a thermoplastic polyurethane film with a thickness of not more than 0.2 mm and a hardness of 65A. The spray density is such that the square resistance is not more than 1000 ohms. After drying, the wires are drawn and the conductive surface is covered in step 8. A field-effect element grid is formed on the pyramid strip coated with ionic liquid, and it is encapsulated with silicon rubber to obtain a flexible force-sensitive sensor element with a total thickness of less than 1 mm;

[0077] 11. Apply a constant 1 volt positive voltage to the grid. Depending on the size of the measurement area and the number of strips, apply a positive voltage of 0.1 to 1 volt between the source and drain electrodes, and the current between the source and drain is compressed as it is applied to the upper surface of the grid The change of the load is used to obtain the standard calibration curve of the sensing element. The calibration curve is used to obtain the load corresponding to the source and leakage current in the load sensitive range, and to obtain the measurement of the unknown load.

Example Embodiment

[0078] Example two

[0079] 1. Same as Example 1, 1;

[0080] 2. Same as Example 1, 2;

[0081] 3. A layer of semiconducting carbon nanotubes is positively coated on the polyurethane elastomer film by the spinning method. The carbon nanotubes are dispersed in toluene solution at a concentration of 0.02mg/ml. The thickness of the carbon nanotube film dispersed on the surface of the pyramid Not more than 10 nanometers, dry at 140°C for 1 hour;

[0082] 4. Same as Example 1, 8;

[0083] 5. Same as Example 1, 9;

[0084] 6. Same as Example 1, 10;

[0085] 7. Same as Example 1, 11.

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PUM

Property	Measurement	Unit
Thickness	500.0	nm
Thickness	<= 0.2	mm
tensile		MPa
Particle size		Pa
strength	10

Description & Claims & Application Information

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Classification and recommendation of technical efficacy words

High sensitivity

Three-dimensional carbon nano-material field effect flexible force sensing element and preparation method

A carbon nanomaterial and sensing element technology, applied in the field of electronic information, can solve the problems of environmental noise suppression, low signal-to-noise ratio, uncertainty of quantitative load measurement, etc., and achieve the effect of high sensitivity

AI-Extracted Technical Summary

Problems solved by technology

Method used

Abstract

Image

Examples

Example Embodiment

Example Embodiment

Example Embodiment

PUM

Description & Claims & Application Information

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