# US 11,897,162 B2 · Piezoresistive sensor material and preparation method and use thereof

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- Number: US 11,897,162 B2
- Document ID: US11897162B2
- Status: Granted
- Kind: B2
- Application number: 17/094,685
- Filed: 2020-11-10
- Published: 2021-05-13
- Granted: 2024-02-13
- Earliest claimed: 2019-11-11
- Assignees: Zhejiang A & Funiversity
- Applicants: Zhejiang A&F University
- Inventors: Xiaoping Shen; Qingfeng Sun; Kangchen Nie; Li Zheng
- Web page: https://patentgrep.com/patent/US11897162B2

## CPC

- B27N 3/02: from particles
- B27N 3/04: from fibres
- B01J 13/0052: {Preparation of gels}
- B27K 3/0207: {Pretreatment of wood before impregnation}
- B27K 3/15: Impregnating involving polymerisation {including use of polymer-containing impregnating agents (macromolecular compounds derived from lignocellulosic materials C08H; compositions of lignin-containing materials C08L97/02)}
- B27K 3/16: Inorganic impregnating agents
- B27N 3/18: Auxiliary operations, e.g. preheating, humidifying, cutting-off
- B27N 5/00: Manufacture of non-flat articles
- B01J 13/0065: {containing an organic phase}
- B01J 13/0091: {Preparation of aerogels, e.g. xerogels}
- B27K 2200/10: Articles made of particles or fibres consisting of wood or other lignocellulosic material
- B27K 2240/00: Purpose of the treatment
- B27N: MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL (containing cementitious material B28B; shaping of substances in a plastic state B29C; fibreboards made from fibrous suspensions D21J; drying F26B17/00)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B27K: PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR (applying liquids or other fluent materials to surfaces in general B05; coating wood or similar material B44D); CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS

## Abstract

The present disclosure provides a method for preparing a piezoresistive sensor material, including: preparing a wood fiber aerogel; conducting dopamine self-polymerization on the surface of the aerogel to obtain a wood fiber-based hydrogel; soaking the wood fiber-based hydrogel in a nano conductive phase suspension or a nano conductive phase precursor to form a conductive phase-loaded wood fiber-based hydrogel; subjecting the conductive phase-loaded wood fiber-based hydrogel to reaction with an aqueous solution including a polyelectrolyte monomer, a crosslinker, an initiator and a catalyst to form a conductive phase-wood fiber-based hydrogel composite; and complexing the composite with metal ions. The present disclosure further discloses a piezoresistive sensor including the sensor material, and a preparation method thereof. The sensor material prepared by the method of the present disclosure has excellent mechanical strength and ionic conductivity, and a sensor further prepared has extremely-high sensitivity.

## Claims

### Claim 1

A method for preparing a piezoresistive sensor material, comprising:
a first step of treating a wood powder with an ionic liquid, and subjecting a resulting wood powder to solation, chemical crosslinking-gelation, and lyophilization to obtain a wood fiber aerogel;
a second step of soaking the aerogel in an alkaline buffer of dopamine hydrochloride to conduct self-polymerization on the surface of the aerogel for 10 hours to 14 hours to obtain a wood fiber-based hydrogel deposited with polydopamine;
a third step of soaking the wood fiber-based hydrogel in a nano conductive phase suspension or a nano conductive phase precursor for 10 hours to 24 hours, and compressing the liquid in the wood fiber-based hydrogel, and repeating the step operations 3 to 5 times to form a conductive phase-loaded wood fiber-based hydrogel;
a fourth step of subjecting the conductive phase-loaded wood fiber-based hydrogel to reaction with an aqueous solution comprising a polyelectrolyte monomer, a crosslinker, an initiator and a catalyst at 40° C. to 60° C. for 12 hours to 24 hours to form a conductive phase-wood fiber-based hydrogel composite; and
a fifth step of soaking the conductive phase-wood fiber-based hydrogel composite in an aqueous solution of a metal ionic compound for 6 hours to 24 hours of complexation to form the piezoresistive sensor material.

### Claim 2 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, wherein the first step further comprises:
adding the wood powder to an ionic liquid of 1-Ethyl-3-methylimidazolium acetate ([EMIM][Ac]) at an amount that is 4% to 6% of the mass fraction of the ionic liquid, and heating and stirring a resulting mixture at 110° C. to 185° C. for 30 min to 24 hours to form a suspension; transferring the above suspension into an acetone aqueous solution with a volume 8 to 10 times that of the suspension and a concentration of 40% to 60% (v/v), and stirring a resulting mixture for 1 hours to 3 hours, subjecting the mixture to suction filtration to obtain a filter cake, and washing the filter cake, and drying the filter cake at 100° C. to 110° C. to obtain a wood fiber;
adding the wood fiber to an aqueous solution comprising 4 wt NaOH and 4 wt % urea to form a suspension, freezing the suspension at −40° C. to −20° C. for 3 hours to 9 hours and thawing at room temperature, and repeating the freezing and thawing treatment 3 to 5 times to obtain a solated wood fiber, wherein the wood fiber and the aqueous solution are mixed at a mass ratio of (0.8-1.5):100;
adding epichlorohydrin (ECH) to the solated wood fiber at a mass 8 to 20 times that of the solated wood fiber, heating and reacting at 40° C. to 60° C. for 1 hours to 6 hours, and washing with water to obtain a chemical crosslinking-gelled wood fiber;
adding 100 mL to 500 mL of a 30% to 90% (v/v) ethanol aqueous solution to the chemical crosslinking-gelled wood fiber, standing for 10 h to 16 h, washing with water, and lyophilizing to obtain a wood fiber aerogel with a density of 0.016 g cm−3 to 0.025 g cm−3.

### Claim 3 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, wherein, the second step further comprises soaking the aerogel in an alkaline tris-hydroxymethylaminomethane-hydrochloric acid buffer of dopamine hydrochloride to obtain the wood fiber-based hydrogel deposited with polydopamine, further wherein the buffer has a dopamine hydrochloride concentration of 1 mg/mL to 3 mg/mL, a tris-hydroxymethylaminomethane concentration of 0.01 mol/L to 0.1 mol/L, and a pH of 8 to 10.5.

### Claim 4 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, further wherein, in the third step, the nano conductive phase suspension is a reduced graphene oxide (rGO) suspension, wherein the rGO suspension is prepared by the following steps:
adding 2 g of graphite powder to 45 mL of concentrated sulfuric acid with a mass fraction of 98% under a 0° C. ice water bath and mechanical stirring, and adding 10 g of potassium permanganate at a rate of about 0.5 g/min to form a suspension;
transferring the above suspension to a 35° C. water bath, and stirring vigorously for 24 h; heating to 90° C., and adding 250 mL of deionized water; stirring a resulting mixture vigorously for 30 min, and cooling to room temperature; adding 10 mL of a 30% (v/v) H2O2 aqueous solution, and thoroughly stirring a resulting mixture; centrifuging the resulting mixture at 10,000 rpm for 15 min, and removing a resulting supernatant; and washing a resulting precipitate with deionized water, and repeating the centrifuging and washing operations 5 times to obtain a graphene oxide (GO) concentrate;
diluting a portion of the GO concentrate to 20 mL with a concentration of 5 mg/mL, and adding 20 mL of 55% (v/v) HI aqueous solution, conducting reduction at room temperature for 6 hours, and conducting dialysis for one week to obtain an rGO suspension precursor; and
adjusting the concentration of rGO to 0.05 mg/mL, 0.1 mg/mL and 0.2 mg/mL, separately, and subjecting resulting solutions to ultrasonication for 15 min to obtain rGO suspensions with three different concentrations.

### Claim 5 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, further wherein, in the third step, the nano conductive phase precursor is a 25 mmol/L to 100 mmol/L silver nitrate aqueous solution.

### Claim 6 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, further wherein, in the fourth step, the polyelectrolyte monomer is a 2.8 mol/L to 3.5 mol/L acrylic acid aqueous solution; the crosslinker is N,N′-methylenebisacrylamide (MBAA), which is added at an amount that is 0.1% to 0.5% of the mass fraction of the polyelectrolyte monomer, the catalyst is tetramethylethylenediamine (TMEDA), added at an amount that is 0.05% to 0.15% of the volume fraction of the aqueous solution, and the initiator is a persulfate comprising ammonium persulfate (APS), added at an amount that is 0.5% to 1.5% of the mass fraction of the polyelectrolyte monomer.

### Claim 7 (depends on 1)

The method for preparing a piezoresistive sensor material according to claim 1, wherein, in the fifth step, the metal ion aqueous solution is an AlCl3 or FeCl3 aqueous solution with a concentration of 0.2 mol/L to 1.0 mol/L.

### Claim 8 (depends on 1)

Use of the piezoresistive sensor material produced by the methods of claim 1 in the preparation of a piezoresistive sensor.

### Claim 9 (depends on 2)

Use of the piezoresistive sensor material produced by the methods of claim 2 in the preparation of a piezoresistive sensor.

### Claim 10 (depends on 3)

Use of the piezoresistive sensor material produced by the methods of claim 3 in the preparation of a piezoresistive sensor.

### Claim 11 (depends on 4)

Use of the piezoresistive sensor material produced by the methods of claim 4 in the preparation of a piezoresistive sensor.

### Claim 12 (depends on 5)

Use of the piezoresistive sensor material produced by the methods of claim 5 in the preparation of a piezoresistive sensor.

### Claim 13 (depends on 6)

Use of the piezoresistive sensor material produced by the methods of claim 6 in the preparation of a piezoresistive sensor.

### Claim 14 (depends on 7)

Use of the piezoresistive sensor material produced by the methods of claim 7 in the preparation of a piezoresistive sensor.

### Claim 15 (depends on 1)

A piezoresistive sensor produced by the methods of claim 1, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode-hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.

### Claim 16 (depends on 2)

A piezoresistive sensor produced by the method of claim 2, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material according into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode-hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.

### Claim 17 (depends on 3)

A piezoresistive sensor produced by the method of claim 3, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.

### Claim 18 (depends on 4)

A piezoresistive sensor produced by the method of claim 4, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material according into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode-hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.

### Claim 19 (depends on 5)

A piezoresistive sensor produced by the method of claim 5, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode-hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.

### Claim 20 (depends on 6)

A piezoresistive sensor produced by the method of claim 6, wherein the method further comprises the steps of:
cutting the piezoresistive sensor material into a suitable size to obtain a hydrogel dielectric layer, comprising a sheet with a length of 1 cm to 3 cm, a width of 1 cm to 3 cm, and a thickness of 0.5 mm to 3 mm, or a sheet with a diameter of 1 cm to 3 cm and a thickness of 0.5 mm to 3 mm;
preparing an electrode-hydrogel dielectric layer-electrode sandwich structure by using the hydrogel dielectric layer and electrode sheets, and drawing out a copper or silver wire with a diameter of 0.1 mm to 0.2 mm and a length of 6 cm to 15 cm as a lead wire on each of the electrode sheets to form a sandwich structure with lead wires; and
encapsulating the sandwich structure with lead wires using polyimide film tape to obtain a piezoresistive sensor.