CN111253751B

CN111253751B - Carbon nanotube polydimethylsiloxane composite material and preparation method and application thereof

Info

Publication number: CN111253751B
Application number: CN202010071030.7A
Authority: CN
Inventors: 王力; 陈俊; 杜健; 史岩彬; 许崇海
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2020-01-21
Filing date: 2020-01-21
Publication date: 2021-09-24
Anticipated expiration: 2040-01-21
Also published as: CN111253751A

Abstract

The invention relates to a carbon nano tube polydimethylsiloxane composite material and a preparation method and application thereof, wherein the carbon nano tube polydimethylsiloxane composite material is prepared from multi-walled carbon nano tubes (MWCNTs) and PDMS, and the mass fraction of the multi-walled carbon nano tubes in the composite material is 8-10%. The mass fraction of the multi-wall carbon nano-tube is 8 wt%, and the multi-wall carbon nano-tube has the maximum elongation and linear piezoresistive range. The method is suitable for being applied to motion detection equipment. The method has the advantages of good sensitivity, good tensile strength and capability of adapting to tensile deformation in the motion detection process.

Description

Carbon nanotube polydimethylsiloxane composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electronic composite materials, and particularly relates to a carbon nano tube polydimethylsiloxane composite material and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

With the arrival of the age of the 5G Internet of things and the increasing importance of people on physical health, portable and wearable equipment capable of realizing real-time health and motion detection is increasingly concerned by people. They exist in the form of flexible skin, portable wristband, wearable electrodes, etc. These devices require detection of physical activity at different sites, from finger motion in the small strain range (< 5% strain) to knee and elbow motion in the large strain range (> 40% strain); different stresses from a gentle human touch (<10kpa) to an operation weight (>100kpa) need to be detected, and therefore, a sensor is required to have new characteristics such as high sensitivity, linearity, a wide stress-strain detection range, simultaneous detection of a plurality of body signals, and the like. Whereas common metal or semiconductor sensors are less sensitive and have poor tensile properties (< 5% strain) and are therefore limited in application. Due to the advantages of excellent mechanical and electrical properties, biocompatibility, low cost and the like, the CNT-PDMS composite material has attracted extensive attention in the aspects of medical diagnosis, health detection, motion detection and the like. The body shadow of the CNT-PDMS can be seen in various types of sensors, such as piezoresistive, capacitive, and piezoelectric sensors.

The principle that the resistance value of the piezoresistive stress sensor of the CNT-PDMS composite material changes in proportion along with strain is utilized, and researches show that the mechanical property and the resistivity of the composite material are influenced by different CNT contents in the CNT-PDMS composite material, so that the piezoresistive property of the sensor is influenced. The sensor is widely researched, and sensors with different shapes and thicknesses can be manufactured by photoetching, casting molding, silk-screen printing, micro-contact printing (transfer printing), spraying, vacuum filtration (vacuum filtration) and other process methods so as to meet different application scenes. Piezoelectric transducers are typically made of a CNT-PDMS composite material on one electrode and a metal or other material on the other, and are capable of generating a voltage when subjected to pressure to achieve different power outputs. However, the sensitivity and tensile strength of the existing CNT-PDMS composite material as a sensor of an electronic device are low, and the CNT-PDMS composite material cannot be well used for a strain sensor for testing the local motion radian of a human body.

Disclosure of Invention

In view of the problems in the prior art, the present invention aims to provide a carbon nanotube polydimethylsiloxane composite material, a preparation method and an application thereof. The ratio of CNT to PDMS directly affects the mechanical and electrical properties of the composite material, and further affects the performance of the sensor. But also influences the physical properties of the composite material, such as viscosity, and the like, so that the composite material is different in applicable processing technology. In our previous studies, it was also found that the properties of CNT-PDMS composites with different mass fractions of CNTs are very different, and in combination with the results of the previous studies, generally speaking, the resistivity of the composite changes most with it and the sensitivity of the sensor is also the greatest near the percolation threshold, but the noise caused by the nonlinearity and high resistance of the response is also the greatest.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a carbon nano tube polydimethylsiloxane composite material (CNT-PDMS) is prepared from multi-wall carbon nano tubes (MWCNTs) and PDMS, wherein the mass fraction of the multi-wall carbon nano tubes in the composite material is 8-10%.

Preferably, the mass fraction of the multi-walled carbon nanotubes is 8%.

Compared with the existing CNT-PDMS composite material, the carbon nanotube polydimethylsiloxane composite material has better sensitivity and tensile strength and is suitable for detecting movement. The linear range of detection is improved.

As the mass fraction of MWCNTs increases, the conductivity increases. The capacitive sensor utilizes less than 3 wt% of the CNT-PDMS composite. The MWCNTs have 8 wt% -10 wt% of mass fraction, high conductivity and high conductivity

The MWCNTs have different mass fraction ranges of flowability and viscosity, and 8 wt% -10 wt% of no flowability is suitable for being used as a solid sensor.

The composite material with the MWCNTs mass fraction of 8 wt% has higher tensile strength and higher elongation. Therefore, the composite material with the MWCNTs mass fraction of 8 wt% has a great advantage in detecting movement with larger strain.

The composite material with the MWCNTs mass fraction of 8 wt% -10 wt% has extremely linearity (R) under the strain range of 0% -40%²>0.99), 8 wt% composites have higher sensitivity and higher tensile strength than 9 wt%, 10 wt% composites, and thus the MWCNTs mass fraction 8 wt% composites of the present invention have a wider stress-strain linearity range.

Motion detection requires not only better sensitivity but also better tensile strength and strain range.

The preparation method of the carbon nano tube polydimethylsiloxane composite material is a dry mixing method or an organic solvent mixing method.

The dry mixing process comprises the following steps: mixing and stirring multi-wall carbon nanotubes (MWCNTs) and PDMS to obtain the carbon nanotube polydimethylsiloxane composite material (CNT-PDMS). The dry blending method does not allow the mixing of the CNTs and PDMS at a molecular level, but allows the CNTs to form many aggregates which are uniformly dispersed in the PDMS.

Preferably, the dry blending temperature is normal temperature, and the temperature range is 22-28 ℃.

The CNT-PDMS capacitive sensor generally requires a sugar template to manufacture a CNT-PDMS composite material with a certain porosity, and different porosities and different CNT concentrations may have different influences on the total impedance, phase angle, dielectric constant, and the like of the composite material.

In a second aspect, the invention provides an application of the carbon nanotube polydimethylsiloxane composite material as a sensor in motion detection equipment.

Preferably, the motion detection device is a bending degree or contraction motion detection device. Further preferably, the motion monitoring bracelet, the motion monitoring glove, the flexible wearable electrode and the like. The composite material of the present invention has a better advantage in the detection of sports equipment. Can adapt to the tensile deformation in the motion detection process.

The preparation method of the carbon nano tube polydimethylsiloxane composite sensor comprises the steps of mixing the CNT-PDMS composite material with a curing agent, then placing the mixture into a mold, and curing to obtain the sensor.

Preferably, the curing temperature is 60-80 ℃, and the curing time is 4-6 h.

The invention has the beneficial effects that:

the carbon nano tube polydimethylsiloxane composite material (CNT-PDMS) provided by the invention can be used for monitoring the movement of different parts of a human body, and has better linearity, sensitivity and stability in detection. The preparation method of the CNT-PDMS composite material is simple and convenient to apply.

The conductivity of the composite material with the MWCNTs mass fraction of 8 wt% -10 wt% is 0.88-2.28S/m.

The MWCNTs mass fraction of 8 wt% has the largest elongation and linear piezoresistive range.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of a preparation process; (a) a sample object picture in the sample manufacturing process (b), wherein the right side is a schematic view of the circular tensile test of a sample (c) with two ends embedded with carbon fibers and a self-made tensile training instrument (d);

FIG. 2 is a graph showing electrical characteristics of CNT-PDMS, (a) V-I characteristic curves of CNT-PDMS composites with different mass fractions of CNT, (b) the conductivity of CNT-PDMS varies with the mass fraction of CNT, (c) impedance analysis of 2 wt% CNT-PDMS composite and its equivalent circuit, and (d) impedance analysis of 10 wt% CNT-PDMS composite;

FIG. 3 is an impedance analysis of CNT-PDMS composites of different CNT mass fractions; (a) 9%, (b) 8%, (c) 7%, (d) 6%, (e) 5%, (f) 4%;

FIG. 4 is a SEM image of a section of a CNT-PDMS composite and a macro-morphology image of the CNT-PDMS composite; (a) SEM image of PDMS cross section. (b) Sectional SEM images of CNT-PDMS composites of 2 wt%, 6 wt% and 10 wt%, respectively. (e) - (h) 2 wt%, 6 wt%, 7 wt%, 10 wt% of the CNT-PDMS composite, respectively;

FIG. 5 is a graph of the mechanical and piezoresistive properties of a CNT-PDMS material; (a-d) are respectively the stress-strain curve, Young's modulus, maximum tensile strength and elongation at break. (e) A resistance change curve of a 6 wt% CNT-PDMS sample when stretched, (f) a resistance change of 6 wt% under 10% cyclic strain, (g) resistance change values under different stresses, and (h) response delay of part of the sample.

FIG. 6 is a graph of the resistance change for various CNT mass fraction CNT-PDMS samples during stretching; (a) 10%, (b) 9%, (c) 8%, (d) 7%, (e) 5%, (f) 4%;

FIG. 7 is a test chart of the CNT-PDMS material sensor prepared in example 1; (a) resistance change generated when an index finger presses the CNT-PDMS composite, (b-c) resistance change generated by bending fingers to different degrees, (d) motion of biceps brachii muscle is detected by using the CNT-PDMS composite material, and (e-f) resistance change during running and walking.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The invention will be further illustrated by the following examples

Example 1

The multiwalled carbon nanotubes (MWCNTs) used are from Suzhou carbonfeng (Suzhou Tanfengchina), with a purity of > 95%, an outer diameter of 8-15nm, a length of 10-20 μm (purity > 95%, outdiameter:8-15nm, length:10-20 μm). PDMS was used as sylgard 184 from Dow Corning (DOW CORNING).

First, 0.8g of CNT is added into 9.9g of PDMS, and then the mixture is stirred by a stirrer at a low speed for 24 hours, thus obtaining 8 wt% of CNT-PDMS composite material.

Example 2

1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 9 wt%, 10 wt% of the CNT-PDMS composite was prepared by the same procedure as in example 1.

Example 3

Standard samples of the same dimensions were cast separately from the composite materials described above with different CNT mass fractions. Before use, the mixed CNT-PDMS composite material is prepared according to the mass ratio of the composite material to a curing agent of 10: 1 adding a curing agent. The composite was then placed in a 3mm x 3mm x 30mm mould with carbon fibres embedded at both ends, and then cured in an oven at 70 ℃ for 5 hours. In the same manner, a standard sample without carbon fiber embedding was prepared, as shown in FIGS. 1(a) (b).

The curing agent is sylgard 184silicone current agent, Chinese translation name: sylgard 184silicone curative. Purchased from Dow Corning, USA, model number sylgard 184.

Test methods of the following experimental examples:

the voltammetry characteristics of the standard samples were measured at 0v to 4v using cyclic voltammetry at an electrochemical workstation (Wanton, Switzerland). And calculating the resistance of the sample according to the slope, and calculating the conductivity sigma of the composite material by the following formula:

wherein S is the cross-sectional area of the sample (m)²) L is the sample length (m), R₀Is the sample resistance (Ω) and σ is the sample conductivity (S/m). Each standard sample was measured 4 times using cyclic voltammetry, and 4 samples were measured for each mass fraction ratio. The impedance test also uses an electrochemical workstation (Switzerland), with a frequency range of 0.1Hz-10 KHz.

The microscopic morphology of the composite material sections with different mass fractions of the CNTs was observed with a field emission scanning electron microscope (field emission scanning electron microscopy) (hitachi Regulus8220) to determine the distribution of the CNTs in the PDMS. The samples were treated by spraying gold before testing.

The standard sample without embedded carbon fibers was subjected to a tensile test using a universal tester (Shimadzu AGS-X5KN, Japan) to study the mechanical properties of the composite and determine the stroke-load curves of the composite with different CNT mass fractions. We focus on the strain sensitive (piezoresistive) properties of CNT-PDMS composites. A standard sample of embedded carbon fibers was clamped using a home-made mini-stretcher (fig. 1(c)), and a cyclic tensile strain of 0% → 5% was performed 15 times at a constant rate (180mm/min) (fig. 1(d)), while the sample resistance value was recorded with a multimeter (agilent 34972A). The same procedure was used for the susceptibility testing at 0 → 10%, 0 → 15%, 0 → 20%, 0 → 25%, 0 → 30%, 0 → 35%, 0 → 40% cyclic strain. 6 samples were tested per mass fraction of composite. The above experiments were all carried out in a constant temperature (26 ℃) room.

Experimental example 1 testing of electrical characteristics

The electrical conductivity of the composite material obtained by mixing CNT as the filler phase material and PDMS as the matrix phase material is the basis for the composite material to have good strain sensitive (piezoresistive) properties, and the composite material can be used for manufacturing sensors because of its excellent strain sensitive properties. To better understand the electrical properties of CNT-PDMS composites, we tested the different CNT mass fraction composites for the safety characteristic curve. As shown in fig. 2(a), we found that all samples exhibited a completely linear foann characteristic curve at voltages of 0-4V. This means that the resistance of the composite material measured using voltammetry is accurate at less large voltages (0-4 v). The multimeter (Agilent) used by us works at a voltage of 0-4v when measuring the resistance. Application of an excessively high voltage causes joule heat to be generated in the composite material and the temperature rises, resulting in reduction of the resistance. This change in resistance should be taken into account for applications requiring a relatively high electric field to be applied across the composite material. It should be noted that the resistance of the carbon fiber embedded in the composite material is only measured to be tens of ohms, and is negligible compared with the resistance of the composite material from hundreds of ohms to tens of mega ohms. Furthermore, we have found that the method of embedding carbon fibers has a lower contact resistance than the method of using conductive copper foil to join composite materials.

Since the electrical resistance of a composite material is related to its geometry, the electrical conductivity, which is independent of the geometry of the material, is more indicative of the electrical properties of the material. Electrical conductivity (electrical conductivity) is a physical quantity used to describe the ease with which charges flow in a substance. As can be seen from fig. 2(b), the electrical conductivity of the composite material shows a tendency to increase as the mass fraction of the CNTs increases, i.e., the electrical conductivity of the composite material is improved. As also apparent in fig. 2(b) and table 1, the conductivity of the CNT-PDMS composite increases by nearly 5 orders of magnitude at 3 wt% compared to 2 wt% and slowly increases and levels off after the CNT doping exceeds 6 wt%. The percolation threshold of the CNT-PDMS composite is therefore between 2 wt% and 3 wt%. Compared to carbon black, metal particles, CNT composites have the lowest percolation threshold. The low percolation threshold of the CNT-PDMS composite may be related to its large aspect ratio. In our tests, CNT-PDMS composites with CNT loadings below 3 wt% are due to too low conductivity (R) ((R))<10^-8S/m) cannot be inPiezoresistive effects were detected in subsequent tests.

Interestingly, impedance analysis (FIG. 2, (c), (d)) and FIG. 3 show that 2 wt% CNT-PDMS composite has not only a resistive but also a capacitive component. While as the mass fraction of the CNT increases, the composite changes from a capacitive and resistive response to a purely resistive response. Therefore, capacitive sensors typically use a low mass fraction of CNT-PDMS composite.

Experimental example 2 surface morphology and macroscopic morphology

The CNT-PDMS composite is capable of conducting electricity due to the conductive pathways formed by the interconnections between the CNTs and due to the quantum tunneling effect that occurs when the CNTs are in close proximity (<10nm), which together determine the conductivity of the CNT-PDMS composite. Fig. 4(a-d) shows SEM photographs of different CNT mass fraction composite sections. It can be seen that the dry blending method does not allow the mixing of the CNTs and PDMS at a molecular level, but allows the CNTs to form many aggregates which are uniformly dispersed in the PDMS. As the mass fraction of CNTs increased, more CNT agglomerates were observed to be dispersed in the PDMS matrix. When the mass fraction of the CNT is lower than the percolation threshold, almost no completely connected conductive network is formed inside the CNT-PDMS composite, or the distance between adjacent CNTs is larger than the minimum distance of quantum tunneling effect, so that the CNT-PDMS composite has the insulation property similar to PDMS. When the mass fraction of CNTs exceeds the percolation threshold, a higher proportion of CNTs in the composite interconnect to form a conductive network and the distance between adjacent CNTs becomes smaller, resulting in a sharp increase in the conductivity of the composite. This explains, on a microscopic scale, the phenomenon of increasing conductivity of the composite as the mass fraction of CNTs increases.

Macroscopically (fig. 4e-f), 1 wt% to 4 wt% of the CNT-PDMS composite material has mobility similar to that of PDMS, and can naturally drop under the action of gravity, and the CNT-PDMS composite material in this state is suitable for most processing technologies, and is generally manufactured into CNT-PDMS sensors in the forms of conductive sponge, aerosol, thin film, and the like. The CNT-PDMS composite material with the weight percent of 5-7 percent is still in a liquid state, but has high viscosity, and cannot generate a uniform film during spin coating, and the CNT-PDMS composite material with the weight percent of 8-10 percent has no fluidity at all, but can be used for processes such as screen printing, casting and the like. Since the viscosity of the composite materials varies greatly for different CNT mass ratios, the applicable process is also different. Therefore, the macroscopic state of the CNT-PDMS composite is also one of the references for selecting a suitable mass fraction of CNTs, and this difference should be considered when preparing the CNT-PDMS composite sensor.

EXAMPLE 3 testing of mechanical Properties

And after the universal testing machine measures a sample stroke-load curve, calculating to obtain a stress-strain curve. Fig. 5(a) is a stress-strain curve of CNT-PDMS composite materials with different mass fractions, and it can be seen that doping CNT into PDMS matrix can not only change its electrical properties, but also significantly change its mechanical properties. In the process of using a universal testing machine to stretch a sample until the sample is broken, the stress-strain curve of the sample better conforms to Hooke's law.

The slope of the stress-strain curve of the sample represents the Young's modulus of the composite, and as shown in FIG. 5(b), the Young's modulus of the CNT-PDMS composite increases significantly with increasing mass fraction of CNT, with the Young's modulus of the pure PDMS sample being 3.34MPa and the Young's modulus of the 10 wt% composite being 10MPa, which are approximately 3 times different. This is because CNTs themselves have great strength (young's modulus >1TPa) and aspect ratio, and as the mass fraction of CNTs increases, more and more CNTs in the composite entangle with each other, thus increasing the elastic modulus of the composite. The maximum tensile strength of the composite (fig. 5(c) and table 1) and young's modulus have a similar trend.

The elongation of the composite (fig. 5(d) and table 1) shows a trend of decreasing first and then increasing as the mass fraction of CNTs increases, with 8 wt% CNT-PDMS composite elongation being the largest. And the elongation of all samples we tested exceeded 40%, there was a good linear relationship of stress-strain for the samples in the 0% to 40% strain range we studied later. The 10 wt% CNT-PDMS composite has a greater tensile strength than the 8 wt% CNT-PDMS composite, but a smaller elongation, because although the 10 wt% composite has more CNTs interconnected inside to increase its tensile strength, it is more easily broken due to stress concentration at some CNT agglomeration places. This means that 8 wt% of the composite is suitable for higher strain applications and 10 wt% is suitable for higher stress applications.

TABLE 1 mechanical Properties of the composites

Experimental example 4 piezoresistive Properties

When a certain tensile stress is applied to the CNT-PDMS composite material, the composite material deforms, which in turn causes a change in the conductivity value of the material, and thus the CNT-PDMS composite material can be used to fabricate a sensor, which utilizes the piezoresistive properties (fig. 5f, fig. 5 h). Due to different conductivities of CNT-PDMS composites with different CNT mass fractions, the initial resistance values of samples with different CNT mass fractions are different, and the initial resistance R of a 3 wt% composite sample₀35682 Ω, the initial resistance of the sample decreased with increasing mass fraction of CNT, 10 wt% composite initial resistance R₀344 Ω, which are 100 times different. We studied the relationship between the resistance change and tensile strain of the composite material under different tensile loads for CNT-PDMS composite materials with different CNT mass fractions. FIG. 5e is a graph of resistance versus time for a 6 wt% CNT-PDMS composite at 0 → 10% cyclic strain, 0 → 15% cyclic strain, 0 → 20% cyclic strain, 0 → 25% cyclic strain, 0 → 30% cyclic strain, 0 → 35% cyclic strain, 0 → 40% cyclic strain, and FIG. 6 is a graph of resistance versus time for a 4 wt%, 5 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% CNT-PDMS composite. A steady change in resistance value was observed over multiple stretching cycles at the same strain. In each stretching cycle, the resistance of the CNT-PDMS composite gradually increased with increasing tensile strain, and reached a maximum at maximum stress, after which the resistance value began to decrease with the shrinkage of the sample. This is because when the composite material is stretched, the distance between adjacent CNTs inside becomes large, and CNT conductive paths that have been formed are formedAnd (4) destroying. Furthermore, the elastic modulus difference between the PDMS matrix material and the CNT is large, and under the same tensile strain, the two strains are different, so that a shear force is generated between the CNT and the PDMS, and an interface between the CNT and the PDMS is damaged, so that the tensile strain increases the resistance of the CNT-PDMS composite material.

Since the internal conductive structure of the un-stretched CNT-PDMS composite is unstable, the initial resistance of the CNT-PDMS composite gradually decreases and eventually stabilizes as the cyclic stretching progresses (fig. 5 e). We calculated the resistance change (Δ R/R) of CNT-PDMS composites of different CNT mass fractions under different tensile strains₀) As shown in fig. 5(g) and table 2, the rate of change of resistance for the same CNT mass fraction of the composite increases with increasing tensile strain. For compounds with different CNT mass fractions, the low CNT mass fraction has large resistance change rate under the same strain, and the sensitivity GF energization reflects the strength of the piezoresistive response:

where GF is the sensitivity, Δ R is the CNT-PDMS composite resistance change value (Ω), R₀Is the initial resistance value (Ω) of the sample,. DELTA.l is the tensile length (mm), and l is the gauge length (mm) of the sample. Fig. 5g and S2 (resistance time plots) show that the resistance change and strain are not completely linear between different samples, so we count the range of linear strain versus resistance change rate for different CNT mass fraction composites, and the sensitivity in the linear piezoresistive response range is shown in table 2. In our assay, piezoresistive responses were not detected because the conductivity of the 1 wt% and 2 wt% composites was too low. Although the 3 wt% compound has high sensitivity in the linear piezoresistive range, the linear range is too narrow, and the resistance change rate is unstable under multiple cyclic stretching in the strain range of 0% -15%. The linear piezoresistive range of the composite with 4 wt% -7 wt% is increased from 0% -30% strain to 0% -35% strain with the mass fraction of the CNT. 8-10 wt% of the compound should be in the range of 0-40%Become extremely linear (R)²>0.99) piezoresistive response. Previous studies have demonstrated that CNT-PDMS composites are linear in stress-strain, so 8 wt% to 10 wt% of the composite has a linear stress-strain-resistance change relationship at 0% to 40% strain. In contrast, 8 wt% composite material has higher sensitivity and higher tensile strength than 9 wt% and 10 wt% composite material, so 8 wt% composite material was selected to detect body movement in subsequent experiments.

TABLE 2 pressure sensitive Properties of CNT-PDMS composites

Experimental example 5 application

As described above, the CNT-PDMS material has an advantage of being remarkably thick in the field of motion detection. We performed simple tests on 8 wt% CNT-PDMS composites. A force (500g) of about 4.9N was applied to the sample at the center with the finger, and as shown in FIG. 7(a), all 7 presses were detected, and a significant resistance change was observed, as well as a difference in the duration of each press. We also examined different degrees of flexion of the finger and the contractile movement of the biceps brachii muscle, respectively, with CNT-PDMS samples. The resistance changes produced by different bending angles of the finger are different, and the strain and thus the resistance change is the greatest when the finger is bent 90 ° (fig. 7 b-c). The CNR-PDMS changes generated by the contraction of biceps brachii muscle can also detect obvious resistance change signals (FIG. 7d), which illustrates the excellent performance of CNT-PDMS as a sensor. Finally, we adhered the CNT-PDMS sample strip to the heel of the shoe and collected the resistance signals of the volunteers (60KG) when running and walking, as shown in FIG. 7(e-f), to clearly distinguish the frequency of running and walking.

And (4) conclusion:

we made CNT-PDMS composites of different mass fractions of CNTs (0 wt% to 10 wt%) by dry blending. And the sectional appearance, mechanical property, electrical property and piezoresistive property of the composite material are characterized. It was found that although the CNT-PDMS composite with a lower CNT mass fraction (3 wt%) had higher sensitivity, it only had a linear piezoresistive response in the 15% -25% strain range and the resistance background noise was large, which was not good for strain detection. With the increase of the mass fraction of the CNT, although the sensitivity of the CNT-PDMS composite material is reduced, the mechanical properties such as the maximum tensile strength and the like of the CNT-PDMS composite material are obviously improved, and the CNT-PDMS composite material shows stable resistance change in a cyclic tensile test under different strains. In summary, 8 wt% of the CNT-PDMS composite has high linear piezoresistive range (0-40% strain) and high sensitivity (1.2097), and is an excellent stress sensing material. In addition, the potential of the CNT-PDMS composite material in the aspect of motion detection is shown.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A carbon nano tube polydimethylsiloxane composite material is characterized in that: the raw materials are multi-wall carbon nano-tubes and PDMS, and the mass fraction of the multi-wall carbon nano-tubes in the composite material is 8%.

2. The method of preparing a carbon nanotube polydimethylsiloxane composite material of claim 1, wherein: dry blending or organic solvent blending.

3. The method of preparing a carbon nanotube polydimethylsiloxane composite material of claim 2, wherein: the dry mixing process comprises the following steps: and mixing and stirring the multi-wall carbon nano tube and the PDMS to obtain the carbon nano tube polydimethylsiloxane composite material.

4. The method of preparing a carbon nanotube polydimethylsiloxane composite material of claim 3, wherein: the dry mixing temperature is normal temperature, and the temperature range is 22-28 ℃.

5. Use of the carbon nanotube polydimethylsiloxane composite of claim 1 as a sensor in a motion detection device.

6. Use of the carbon nanotube polydimethylsiloxane composite of claim 5 as a sensor in a motion detection device, wherein: the motion detection device is a device for detecting a degree of bending or a contraction motion.

7. Use of the carbon nanotube polydimethylsiloxane composite of claim 6 as a sensor in a motion detection device, wherein: the motion detection equipment is a motion monitoring bracelet, a motion monitoring glove and a flexible wearable electrode.