CN111084975A

CN111084975A - Leather-based pressure sensor for recording walking track, preparation method and application

Info

Publication number: CN111084975A
Application number: CN201911357853.XA
Authority: CN
Inventors: 罗晓民; 蒋雯; 张鹏; 冯见艳; 秦荣; 刘丽成
Original assignee: Shaanxi University of Science and Technology
Current assignee: Shaanxi University of Science and Technology
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2020-05-01
Anticipated expiration: 2039-12-25
Also published as: CN111084975B

Abstract

The invention discloses a preparation method of a leather-based pressure sensor for recording a walking track. The method comprises the following specific steps: (1) preparing the complex three-dimensional conductive leather with coordination bonding; (2) manufacturing the double-layer conductive leather into a piezoresistive sensor through a high polymer material bonding layer; (3) the single-point pressure sensors are assembled into a dense array type pressure sensor to construct a uniform micro-nano structure conductive network; (4) the dense array type sensors are arranged on the soles, and applied and released pressure is converted into electric signals to detect the walking rule of the human body, so that the reasonable movement and fitness planning are realized. The preparation method of the pressure sensor for recording the walking track based on the conductive leather improves the compression stress, enhances the rebound resilience, improves the stability, is comfortable to wear, is moisture permeable and breathable, and can monitor the motion rule of the human body in real time and plan reasonable body-building motion.

Description

Leather-based pressure sensor for recording walking track, preparation method and application

Technical Field

The invention belongs to the technical field of conductive leather, and discloses a preparation method of a leather-based pressure sensor for recording a walking track.

Background

As an important branch of wearable electronics, flexible pressure sensors have been investigated for a wide range of applications, such as human-machine interfaces, electronic skins, health monitoring, and certain application-driven functions. Especially, people pay more and more attention to health, and reasonable monitoring of motion rules has important significance for guiding the health of people. Running and walking are necessary exercises for people every day, reasonable exercise, tumbling and postoperative recovery conditions of the human body are guided and detected through running and walking data, and the method has epoch-spanning significance for the development of human healthy life.

Conventional pressure sensors monitor signal flow by regulating the contact resistance between conductive materials as the substrate deforms. However, the sensor has small compression rebound deformation, poor stability and low sensitivity. Because the contact resistance between the conductive substances at the local complicated pressure distribution condition cannot be uniformly controlled, no linear relation exists between the pressure and the relative resistance, and high sensitivity and high pressure monitoring range cannot be simultaneously obtained. Moreover, after the pressure is removed, the indirect contact resistance of the conductive substance is recovered slowly, so that a large hysteresis loop exists between the devices, and the accuracy of the devices is influenced. The construction of a conductive network with a uniform micro-nano structure is often used to improve the performance of the device and to detect the change of mechanical signals in different complex environments.

Leather is a traditional wearable material, the wearing comfort level is high, the air permeability is good, the biocompatibility is good, the inherent three-dimensional heterostructure of the leather and the abundant functional groups of the collagen fibers of the leather enable the leather to be more easily loaded and combined with a conductive material, and therefore the dead skin has the possibility of recovering the sensing capability. In the prior art, a method for detecting and guiding human body healthy movement by a pressure sensor prepared by coordinative bonding of a conductive carbon material and leather collagen fibers is not available for a while.

Disclosure of Invention

The pressure sensor for recording the walking track based on the conductive leather is prepared by using raw materials such as graphene, reduced graphene oxide, single-walled or multi-walled carbon nanotubes, transition metal ions, natural leather and the like, using the conductive leather as a conductive layer and using a high polymer material as an adhesive layer. The invention solves one or more of the problems, the preparation method is quick, simple and environment-friendly, and the obtained leather-based pressure sensor can sensitively obtain related data and ensure the comfort of the flexible sensor during wearing.

In order to achieve the purpose, the invention adopts the technical scheme that:

the preparation method of the leather-based pressure sensor for recording the walking track comprises the following steps:

1) preparing the complex three-dimensional conductive leather with coordination bonding;

the three-dimensional conductive leather with coordination bonding composite comprises a bridging agent which is transition metal ions and is obtained by firmly combining conductive carbon materials such as graphene and carbon nano tubes with leather collagen fibers through coordination bonding.

The three-dimensional conductive leather with coordination bonding composite comprises one or more transition metal ions of iron, aluminum, chromium, zirconium and titanium, a conductive carbon material of graphene, reduced graphene oxide and multi-wall or single-wall carbon nano tubes, and a leather body of cowhide, pigskin, donkey skin, rabbit skin and sheepskin.

2) Manufacturing the double-layer conductive leather into a piezoresistive sensor through a high polymer material bonding layer;

the piezoresistive sensor is obtained by manufacturing a double-layer sandwich structure by using conductive leather as a surface layer and polymer materials as an adhesive layer, wherein the conductive leather is first leather and second leather respectively.

The piezoresistive sensor comprises a high polymer material which is one of polyurethane, polyvinyl alcohol, polyvinyl chloride, polyacrylic acid, polystyrene and polycarbonate.

The leather comprises a first leather body and a conductive carbon material, wherein the first leather body is compounded with the conductive carbon material, the range of the resistivity of the first leather is 0.96 omega-cm-1.28 k omega-cm, the second leather comprises the leather body and the conductive carbon material, the second leather body is compounded with the conductive carbon material, and the range of the resistivity of the second leather is 0.96 omega-cm-1.28 k omega-cm.

3) The single-point pressure sensors are assembled into a dense array type pressure sensor to construct a uniform micro-nano structure conductive network;

the pressure sensor is arranged on the sole in a single unit, different multiple unit array, multiple unit dense array or integral attachment mode.

The pressure sensor comprises one or more of a circular array, a rectangular array, a triangular array and an irregular array in a single unit, a plurality of unit arrays and a plurality of unit dense arrays.

4) The dense array type sensors are arranged on the soles, and applied and released pressure is converted into electric signals to detect the walking rule of the human body, so that the reasonable movement and fitness planning are realized.

The pressure generated by running postures, walking postures and frequency thereof is converted into an electric signal to judge the walking step number, the walking rule and the posture standardization degree, and reasonably plan and guide the exercise health index.

Specifically, the method comprises the following steps:

(1) preparation of composite three-dimensional conductive leather with coordination bonding

Reduced graphene oxide, acidified carbon nanotubes and a transition metal ion solution are mixed. Taking MWCNT/RGO mass ratios as 3:0, 3:1, 3:2 and 3:3 respectively, ultrasonically dispersing in NMP to prepare 0.2 mg/mL dispersion, and mixing with transition metal ion solutions with different ratios, wherein M isⁿ⁺And the/C is 0.01, 0.02, 0.03, 0.04, 0.08 and 0.16 mmol/mg respectively, stirring and reacting for 2-3h at room temperature, soaking leather with a certain area in a mixed solution for 1 h under the assistance of ultrasonic waves at a certain pH, then carrying out half-drying treatment at 50 ℃, and carrying out hot pressing for 10-30 min to enable the surface of the collagen to be assembled for the second time.

(2) Preparation of pressure sensor

Two pieces of conductive leather with different sizes are cut out and respectively used as a first leather and a second leather, and a high polymer material is used as a bonding layer to manufacture the sandwich structure pressure sensor.

(3) Preparation of dense array type pressure sensor

The pressure sensors of the single unit array are assembled into a dense array type pressure sensor in a circular/rectangular/triangular/irregular shape array. The dense array type pressure sensor is arranged at the sole, and the walking rule is recorded by applying and releasing a current signal generated by pressure deformation to the dense array type pressure sensor.

Through optimizing experimental conditions, the preferable technical scheme is as follows: the conductive carbon material in the conductive leather has the mass ratio of MWCNT to RGO of 3:1, and the transition metal ion is Co²⁺The leather is a second layer leather;

through optimizing experimental conditions, the preferable technical scheme is as follows: the conductive leather contains Co²⁺The concentration of the catalyst is 0.08 mmol/mg;

through optimizing experimental conditions, the preferable technical scheme is as follows: the pH value of the conductive leather is 7, and the reaction time is 2.5 h;

through optimizing experimental conditions, the preferable technical scheme is as follows: the electric iron in the conductive leather is naturally dried after being hot-pressed for 20 min;

through optimizing experimental conditions, the preferable technical scheme is as follows: the polymer material in the pressure sensor is polyurethane;

through optimizing experimental conditions, the preferable technical scheme is as follows: the array type pressure sensor is irregular in shape;

through optimizing experimental conditions, the preferable technical scheme is as follows: the array type pressure sensor is a dense array type pressure sensor;

the invention has the beneficial effects that:

(1) according to the invention, the coordination bonding is used for preparing the conductive leather as the three-dimensional conductive flexible substrate, the conductivity and the tolerance are high, the high polymer material is used as the middle layer to combine with the conductive leather to construct the uniform micro-nano structure conductive network to prepare the dense array pressure sensor, the compression stress is improved, the rebound resilience is enhanced, and the stability is improved.

(2) The leather is used as the base material, the front-edge heat point is combined with the traditional material, the leather sensing capability is endowed for detecting the motion rule of the human body to guide the health of the human body, the multifunctional application of the leather is enriched, and the leather has practical significance for guiding the life health.

(3) The invention has simple preparation process, low cost of raw materials, high wearing comfort of air and moisture permeation and is beneficial to popularization and application.

Drawings

FIG. 1 is an SEM photograph of the natural leather and the conductive leather prepared in example 3, the conductivity being 1.36. omega. cm, and the sheet resistance being 9.87. omega./sq;

FIG. 2 is a diagram of a dense array pressure sensor prepared in example 3;

FIG. 3 is a graph of current versus time at 100G and 200G at 3V for a dense array pressure sensor prepared in example 3;

FIG. 4 is a schematic structural view of a pressure sensor made in accordance with the present invention; wherein: 1-a first conductive layer; 2-a tie layer; 3-a second conductive layer.

Detailed Description

The present invention will be further illustrated with reference to the following examples, but the present invention is not limited to the following examples.

Example 1

Step 1: taking the mass ratio of MWCNT to RGO as 3:0, ultrasonically dispersing in NMP to prepare 0.2 mg/mL solution, and then mixing with Al³⁺Mixing the solution, wherein Al³⁺Respectively adding 0.01mmol/mg of collagen C and pH of 3, stirring at room temperature for reaction for 2h, ultrasonically and auxiliarily soaking pigskin in 30mL of mixed solution, drying at 50 ℃ for half drying, and hot pressing with an electric iron for 10 min to perform secondary assembly on the surface of the collagen;

step 2: cutting two pieces of conductive leather with different sizes to respectively serve as a first leather and a second leather, and using polyvinyl alcohol as an adhesive layer to manufacture a sandwich structure pressure sensor;

and step 3: the pressure sensors of the single unit array are assembled into a dense array type pressure sensor in a circular array, the dense array type pressure sensor is arranged at the sole, and the walking rule is recorded through current signals generated by applying and releasing pressure deformation to the dense array type pressure sensor.

Example 2

Step 1: taking the mass ratio of MWCNT to RGO as 3:1, ultrasonically dispersing in NMP to prepare 0.2 mg/mL solution, and then mixing with Cr³⁺Mixing the solutions, wherein Cr³⁺the/C is 0.02 mmol/mg, the pH is 11, the reaction is carried out for 3 hours under the stirring at the room temperature, the sheepskin is soaked in 30mL of mixed solution under the ultrasonic assistance, the drying is semi-dried at the temperature of 50 ℃, and the secondary assembly is carried out on the surface of the collagen by the hot pressing of an electric iron for 30 minutes;

step 2: cutting two pieces of conductive leather with different sizes to respectively serve as a first leather and a second leather, and using polyvinyl chloride as a bonding layer to manufacture a sandwich structure pressure sensor;

and step 3: the pressure sensors of the single unit arrays are arranged at the soles of the feet, and the walking rule is recorded by applying and releasing current signals generated by pressure deformation to the pressure sensors of the single unit arrays.

Example 3

Step 1: taking the mass ratio of MWCNT to RGO as 3:1, ultrasonically dispersing in NMP to prepare 0.2 mg/mL solution, and then mixing with Co²⁺Solution mixing of Co therein²⁺the/C is 0.08 mmol/mg, the pH is 7, the stirring reaction is carried out for 2.5 hours at room temperature, the bovine cortex II is soaked in 30mL of mixed solution with the assistance of ultrasound, the mixture is semi-dried at 50 ℃, and an electric iron is used for carrying out hot pressing for 20 min to carry out secondary assembly on the surface of the collagen;

step 2: cutting two pieces of conductive leather with different sizes to respectively serve as a first leather and a second leather, and using polyurethane as a bonding layer to manufacture a sandwich structure pressure sensor;

and step 3: the pressure sensors of the single unit array are assembled into a dense array type pressure sensor in an irregular array, the dense array type pressure sensor is arranged at the sole, and the walking rule is recorded through current signals generated by applying and releasing pressure deformation to the dense array type pressure sensor.

Fig. 1 is an SEM image of the natural leather and the conductive leather prepared in this example. Fig. 1(a) is a SEM image of natural leather, and fig. 1(b) is a SEM image of composite flexible conductive leather, and the results show that the composite flexible conductive leather prepared in the present example has an excellent three-dimensional conductive network;

FIG. 2 is a diagram of a dense array sensor fabricated in this example. Wherein the conductivity of the conductive leather is 1.36 omega cm, and the sheet resistance is 9.87 omega/sq;

FIG. 3 is a graph of current versus time at 100G and 200G at 3V for the dense array pressure sensor prepared in this example.

Example 4

Step 1: taking the mass ratio of MWCNT to RGO as 3:2, ultrasonically dispersing in NMP to prepare 0.2 mg/mL solution, and then Ti⁴⁺Solution mixing of Ti⁴⁺The concentration/C is 0.16 mmol/mg, the pH value is 7, the stirring reaction is carried out for 2 hours at room temperature, the bovine cortex II is soaked in 30mL of mixed solution with the assistance of ultrasound, the mixture is semi-dried at 50 ℃, and an electric iron is used for carrying out hot pressing for 30 min to carry out secondary assembly on the surface of the collagen;

step 2: cutting two pieces of conductive leather with different sizes to respectively serve as a first leather and a second leather, and using polyacrylic acid as an adhesive layer to manufacture a sandwich structure pressure sensor;

and step 3: the pressure sensors of the single unit array are assembled into a dense array type pressure sensor in a rectangular array, the dense array type pressure sensor is arranged at the sole, and the walking rule is recorded through current signals generated by applying and releasing pressure deformation to the dense array type pressure sensor.

Example 5

Step 1: taking the mass ratio of MWCNT to RGO as 3:3, ultrasonically dispersing in NMP to prepare 0.2 mg/mL solution, and then Fe³⁺Mixing the solution, wherein Fe³⁺the/C is 0.16 mmol/mg, the pH is 11, the reaction is carried out for 3 hours under the stirring at the room temperature, the sheepskin is soaked in 30mL of mixed solution under the ultrasonic assistance, the drying is carried out at the temperature of 50 ℃ for half drying, and the electric iron is used for carrying out hot pressing for 30 min so as to carry out secondary assembly on the surface of the collagen;

Claims

1. a leather-based pressure sensor for recording the walking track, comprising the first conductive layer and the second conductive layer, the first conductive layer and the second conductive layer are connected by an adhesive layer, it is characterized in that, the first conductive layer and At least one layer in the second conductive layer is conductive leather, and the conductive leather is obtained by a method comprising the following steps:

The transition metal ion Mn ⁺ is used as a bridging agent, and the conductive carbon material is firmly combined with the active groups in the leather through coordination bonding.

2. The sensor of claim 1, wherein the conductive leather is obtained by a method comprising the steps of:

The conductive carbon material adopts at least one of reduced graphene oxide rGO and acidified carbon nanotube MWCNT; the conductive carbon material is mixed into the transition metal ion solution and dispersed uniformly;

After the transition metal ions are fully adsorbed on the surface of the conductive carbon material, the transition metal ion-conductive carbon material dispersion is fully contacted with the leather by impregnation, ultrasonic-assisted impregnation, or the dispersion penetrates the leather to achieve transition metal ion-conductivity. Assembly of carbon material in leather.

3 . The sensor according to claim 1 or 2 , wherein the electrical resistivity of the conductive leather is 0.96 Ω·cm to 1.28 kΩ·cm. 4 .

4. the preparation method of the leather-based pressure sensor for recording the walking track, is characterized in that, comprises the following steps:

Using transition metal ions as bridging agent, through coordination bonding, the conductive carbon material is firmly combined with the active groups in the leather to obtain conductive leather;

The first conductive layer and the second conductive layer are bonded through an adhesive layer, and at least one of the first conductive layer and the second conductive layer is conductive leather.

5. The method of claim 4, wherein the conductive leather is obtained by a method comprising the following steps:

The conductive carbon material adopts at least one of reduced graphene oxide and acidified carbon nanotubes; the conductive carbon material is mixed into the transition metal ion solution to be uniformly dispersed;

After the transition metal ions are fully adsorbed on the surface of the conductive carbon material, the transition metal ion-conductive carbon material dispersion is fully contacted with the leather by means of dipping, ultrasonic-assisted dipping, and the dispersion penetrates the leather, so as to realize the transition metal ion-conductive carbon material. Assembly of materials in leather.

6. The method of claim 4, wherein the transition metal ion species is one or more of iron, aluminum, chromium, zirconium, and titanium; the conductive carbon material is graphene, reduced graphite oxide One or more of alkene, multi-walled or single-walled carbon nanotubes; the leather is one of cowhide, pigskin, donkey skin, rabbit skin, and sheepskin.

7. The method of claim 4, wherein the adhesive layer is obtained by curing a polymer binder, and the polymer binder is polyurethane, polyvinyl alcohol, polyvinyl chloride, polyacrylic acid, polystyrene, or polycarbonate.

8. The method of claim 4, comprising the steps of:

1) The reduced graphene oxide, acidified carbon nanotubes and transition metal ion solution were mixed with MWCNT/rGO mass ratio of 3:(0-3), ultrasonically dispersed in N-methylpyrrolidone NMP to prepare a 0.2 mg/mL solution, and then Mixed with transition metal ion solutions of different proportions, wherein the ratio of transition metal ions to carbon in reduced graphene oxide and acidified carbon nanotubes M ⁿ⁺ /C is 0.01-0.16 mmol/mg, and the reaction is stirred at room temperature for 2-3h; under a certain pH , the leather was immersed in the mixed solution with ultrasonic assistance for 1 h, dried at 50 °C for semi-drying, and hot-pressed with an electric iron for 10-30 min to assemble the collagen surface for the second time;

2) Cut two pieces of conductive leather with different shapes and sizes as the first conductive layer and the second conductive layer respectively, and the polymer material as the bonding layer to make a single-point pressure sensor; the single-point pressure sensor is assembled into a dense array pressure sensor Construct a uniform micro-nano structured conductive network.

9. The application of the conductive leather-based pressure sensor prepared by the method of any one of claims 4-8 in recording the walking track.

10. The application according to claim 9, wherein the single-point pressure sensor is made into a pressure sensor array and installed on the sole; when the local pressure in the pressure sensor array changes, the pressure sensor in the pressed part sends an electrical signal .