CN108489375B

CN108489375B - Manufacturing method of two-dimensional sensor based on carbon nano tube

Info

Publication number: CN108489375B
Application number: CN201810114695.4A
Authority: CN
Inventors: 刘遵峰; 李俊
Original assignee: Changzhou University
Current assignee: Changzhou University
Priority date: 2018-02-06
Filing date: 2018-02-06
Publication date: 2022-10-28
Anticipated expiration: 2038-02-06
Also published as: CN108489375A

Abstract

The invention provides a method for manufacturing a two-dimensional sensor based on carbon nano tubes, which comprises the following steps of firstly, preparing the carbon nano tubes by a chemical vapor deposition method; and preparing the carbon nano tube into a uniaxial sample and a biaxial sample, thereby preparing the uniaxial two-dimensional sensor and the biaxial two-dimensional sensor. The two-dimensional sensor manufactured by the method has good resistance change rate in the horizontal direction and the vertical direction which are perpendicular to each other, and the sensor has good sensitivity.

Description

Manufacturing method of two-dimensional sensor based on carbon nano tube

Technical Field

The invention relates to the technical field of sensors, in particular to a manufacturing method of a two-dimensional sensor based on carbon nano tubes.

Background

The sensor, as the name implies, is an instrument that transmits a "sensation"; the so-called "sensation" is reflected in the field of natural science in various physical and chemical signals. The sensor may convert some physical signal into another observable or measurable (electrical, optical) signal. Common sensors include temperature sensors (thermistors, thermocouples), pressure sensors, displacement sensors, strain sensors (strain gauges), optical sensors (photodiodes), chemical sensors, and biosensors.

Strain sensors, also known as strain gauges, which convert strain into an electrical signal output, are based on measuring the strain of an object caused by a force applied to the object. The method has wide application in the fields of mechanics, medicine, material science, construction and the like.

Electronic devices that are stretchable, foldable, or otherwise deformed into complex curvilinear shapes may be provided with many new functions that previously have not been possible with rigid electronic components. These electronic devices can function well on displays, cameras for electronic eyes and skin sensors. One method that has been developed in recent years for the development of flexible conductors is to create a layer of corrugated or mesh-like conductive structure and place it on a pre-stretched elastomeric substrate. For different elastic conductors, such as metal-coated mesh plates, corrugated metal wires or two-dimensional metal films, have been disclosed in the prior art.

Carbon nanotubes have a large aspect ratio, good electrical conductivity, high thermal and mechanical strength. Theoretical calculations indicate that the tensile strength and elastic modulus of carbon nanotubes are high, on the order of Tpa, and experimentally confirmed. The carbon nano tube has very obvious elastic response to deformation, and the theoretical calculation method shows that the breaking strain of the carbon nano tube is between 15% and 18%. Which makes them promising for retractable conductors. Although carbon nanotubes have been studied deeply in the aspect of flexible transparent electrodes, there is a great deal of research space in the aspect of stretchability. Recently, a composite sheet composed of carbon nanotubes, an ionic liquid and a fluorinated copolymer, which exhibits excellent conductivity when stretched as an elastic conductor, has been proposed. The elastic conductor can maintain good conductivity even when stretched by 700%. However, their electrical conductivity will still decrease linearly with strain.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: in order to overcome the defects in the prior art, the invention provides a method for manufacturing a two-dimensional sensor based on carbon nano tubes, which adopts a flexible conductor to manufacture a two-dimensional strain sensor through resistance changes generated by different stretching conditions of the flexible conductor in the horizontal direction and the vertical direction.

The technical scheme adopted for solving the technical problems is as follows: a manufacturing method of a two-dimensional sensor based on carbon nano tubes comprises the following steps:

step 1: preparing carbon nanotubes by a chemical vapor deposition method;

step 1.1: taking iron (1 nm)/aluminum oxide (10 nm) placed on a silicon wafer as a catalyst, taking ethylene as a carbon source, taking a mixed gas of argon and hydrogen as a carrier gas, maintaining the environment at 750 ℃, forming multi-wall carbon nano-tube CNT on the surface of the catalyst, and synthesizing the CNT array on a quartz tube furnace through chemical vapor deposition;

step 1.2: scraping the CNT thin slice from the CNT array by a blade; adhering the stretched CNT to the edge part of the CNT array by using a blade, and continuously extracting to form a CNT sheet;

step 2: sample preparation, including uniaxial sample preparation or biaxial sample preparation;

SEBS rubber is used as the flexible substrate of the CNT in the preparation of the sample, and preferably, the SEBS rubber is manufactured by Komatsu corporation, G-1651H. The shape of the SEBS rubber can be any shape and size, the SEBS rubber can be selected according to user requirements, square SEBS rubber is selected according to the invention for facilitating comparison of transverse and longitudinal characteristics, the stretching ratio depends on the stretching performance of the SEBS, the stretching ratio is preferably 4 times, and the size requirement of the CNT sheet is that the SEBS serving as the flexible substrate is larger than the size of the carbon nanotubes.

A uniaxial sample was prepared and,

taking a square SEBS rubber (50 mm multiplied by 50 mm), and stretching the SEBS rubber by 4 times in the transverse direction and the longitudinal direction respectively; two sections of CNT (carbon nanotube) sheets (50 mm multiplied by 40 mm) are transversely placed on the SEBS rubber to obtain a single-axis two-dimensional sensor, and the manufacture of a single-axis sample is completed; when the CNT is taken down from the silicon wafer, alcohol is generally dripped on the SEBS, the CNT is fully connected with the SEBS, and the alcohol is volatilized, so that the test is not influenced.

The preparation of a biaxial sample was carried out,

a square block of SEBS rubber (50 mm. Times.50 mm) was taken and stretched 4 times each in the transverse and longitudinal directions. And (3) transversely placing a section of CNT sheet (50 mm multiplied by 40 mm) on the SEBS rubber, and longitudinally placing a section of CNT sheet (50 mm multiplied by 40 mm) on the SEBS rubber to obtain the biaxial two-dimensional sensor, thereby completing the preparation of the biaxial sample. Two CNT sheets are stacked perpendicular to each other.

The invention has the beneficial effects that: according to the manufacturing method of the two-dimensional sensor based on the carbon nano tube, the two-dimensional sensor manufactured by the method has good resistance change rate in the mutually vertical horizontal direction and vertical direction, and the sensor is more sensitive when the change rate is larger.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a flow chart of the fabrication of a two-dimensional carbon nanotube-based sensor according to the present invention;

FIG. 2 (a) is an SEM image of uniaxial sample surface CNT flakes at low magnification;

FIG. 2 (b) is an SEM image of uniaxial sample surface CNT flakes at high magnification;

FIG. 2 (c) is an SEM image of biaxial sample surface CNT flakes at low magnification;

FIG. 2 (d) is an SEM image of biaxial sample surface CNT flakes at high magnification;

FIG. 3 (a) is a schematic of a uniaxial sample stretched in the horizontal direction;

FIG. 3 (b) is a graph of the horizontal direction stretch of a uniaxial sample as a function of the rate of change of resistance;

FIG. 3 (c) is a schematic of the vertical direction stretching of a uniaxial sample;

FIG. 3 (d) is a graph showing the relationship between the vertical direction elongation and the rate of change in resistance of a uniaxial sample;

FIG. 4 (a) is a schematic of a biaxial sample stretched in the vertical direction;

FIG. 4 (b) is a graph showing the relationship between the perpendicular direction stretching and the rate of change in resistance of a biaxial sample;

Detailed Description

The present invention will now be described in detail with reference to the accompanying drawings. This figure is a simplified schematic diagram, and merely illustrates the basic structure of the present invention in a schematic manner, and therefore it shows only the constitution related to the present invention.

As shown in fig. 1, a method for manufacturing a two-dimensional sensor based on carbon nanotubes according to the present invention comprises the following steps: the method comprises the following steps:

step 1: preparing carbon nanotubes by chemical vapor deposition;

The uniaxial sample preparation was carried out by,

taking a square SEBS rubber (50 mm multiplied by 50 mm), and stretching the SEBS rubber by 4 times in the transverse direction and the longitudinal direction respectively; taking two sections of CNT sheets (50 mm multiplied by 40 mm) to be transversely placed on the SEBS rubber, vertically stacking the two sections of CNT sheets in the same placing direction to obtain a single-axis two-dimensional sensor, and finishing the manufacture of a single-axis sample;

the preparation of a biaxial sample was carried out,

And (3) evaluating and testing the performance of the prepared two-dimensional sensor, wherein the test articles comprise silver colloid and a Keithley2400 multimeter.

(1) Characterization of carbon nanotubes

Carbon nanotubes were prepared by chemical vapor deposition, and they were fabricated as uniaxial and biaxial samples, respectively. SEM images of the obtained scanning electron microscope images were taken at different magnifications. Fig. 2 (a) and 2 (b) are SEM images at low magnification and high magnification, respectively, of a uniaxial sample. It can be seen from the figure that the uniaxial sample surface has a regular corrugation structure. Fig. 2 (c) and 2 (d) are SEM images at low magnification and high magnification, respectively, of a biaxial sample. It can be seen that the surface of the biaxial sample is different from the wrinkle structure of the uniaxial sample, and is a new wrinkle structure formed after combining the longitudinal wrinkles and the transverse wrinkles. CNT sheet width can be controlled in the millimeter to centimeter range by varying the width of the blade and CNT array contact, with CNT thickness typically tens of nanometers. The present invention is primarily concerned with CNT flakes having an average diameter of 7nm and a column thickness of approximately 300 μm.

(2) Tensile Property test of uniaxial samples

As shown in fig. 3 (a), three positions which do not overlap with each other are selected on the uniaxial sample and are numbered as 1, 2 and 3, and the conductive silver paste is coated on the three positions, and the three positions can be selected arbitrarily but cannot overlap with each other. Stretch 50%, 100%, 150%, 200%, 250% slowly in the 1 to 2 direction (i.e., horizontal direction). Measuring the resistance R between any two points of 1, 2 and 3 by using a Keithley2004 multimeter once each stretching ₁₂ 、R ₁₃ 、R ₂₃ . Then slowly retract 50%, 100%, 150%, 200%, 250% in the 21 direction. While the resistance R 'between any two

points

1, 2 and 3 was measured with a Keithley2004 multimeter at each retraction' ₁₂ 、R' ₁₃ 、R' ₂₃ . The rate of change of resistance can be calculated according to the formula Δ R = R-R0, where R is the resistance value measured using Keithley2004 and R0 is the resistance value before the non-stretching.

FIG. 3 (b) is a graph showing the relationship between the horizontal elongation and the rate of change in resistance. The resistance change rates in the 12-, 23-and 31-directions become larger as the stretching becomes larger and become smaller as the stretching becomes smaller. However, in the 12 direction, the rate of change in resistance under the same stretching conditions was relatively smaller than the rates of change in resistance in the 23 direction and the 13 direction. This is because the resistance is stretched and shortened in the direction of the wrinkle in the 12 direction, and the resistance change is relatively small.

As shown in fig. 3 (c), the stretching is slowly performed in the direction perpendicular to 12 by 50%, 100%, 150%, 200%, 250%. Measuring the resistance R between any two points of 1, 2 and 3 by Keithley2004 every time of stretching ₁₂ 、R ₁₃ 、R ₂₃ . Then slowly retracting 50%, 100%, 150%, 200%, 250% in the direction perpendicular to 21. While measuring the resistance R 'between any two

points

1, 2 and 3 by Keithley2004 at each retraction' ₁₂ 、R' ₁₃ 、R' ₂₃ The resistance change rate can be calculated according to the formula Δ R = R-R0.

FIG. 3 (d) is a graph showing the relationship between the elongation in the vertical direction and the rate of change in resistance. The resistance change rates in the 23 direction and the 31 direction become larger as the stretching becomes larger, and become smaller as the stretching becomes smaller, the resistance change rates show a change that approaches a straight line all the time. However, in the 12-direction, the rate of change in resistance hardly linearly changes with the stretching or shortening of the sample. This is because the folds of the carbon nanotubes are hardly pulled apart when the sample is stretched and shortened in a direction perpendicular to the direction of the folds, and thus, the resistance is hardly significantly changed.

(3) Biaxial specimen tensile Property test

The variation of a uniaxial sample in the direction perpendicular to the fold is not significant and is a significant disadvantage as a two-dimensional sensor. To solve the problem that the change of the sensor in the direction perpendicular to the wrinkles is not significant, a biaxial sample was made. As shown in fig. 4 (a), three positions are selected on the biaxial sample and numbered as 1, 2 and 3, and the conductive silver paste is applied to the three positions, which can be arbitrary but cannot be overlapped with each other. Stretching slowly along the direction perpendicular to 12 by 50%, 100%, 150%, 200%, 250%. Measuring the resistance R between any two points of 1, 2 and 3 by Keithley2004 every time of stretching ₁₂ 、R ₁₃ 、R ₂₃ . Then slowly retracting 50%, 100%, 150%, 200%, 250% along the direction perpendicular to 21. While measuring the resistance R 'between any two

points

1, 2 and 3 with Keithley2004 at each retraction' ₁₂ 、R' ₁₃ 、R' ₂₃ The resistance change rate can be calculated according to the formula Δ R = R-R0.

FIG. 4 (b) is a graph showing the relationship between the horizontal elongation and the rate of change in resistance. The resistance change rates in the 12-, 23-and 31-directions become larger as the stretching becomes larger and become smaller as the stretching becomes smaller. As can be seen from the figures, the biaxial sample successfully solved the problem that the change in the rate of resistance was not significant when the uniaxial sample was stretched and shortened perpendicular to the direction of wrinkles.

The arrows in the figure indicate the direction of stretching.

In light of the foregoing description of preferred embodiments in accordance with the invention, it is to be understood that numerous changes and modifications may be made by those skilled in the art without departing from the scope of the invention. The technical scope of the present invention is not limited to the contents of the specification, and must be determined according to the scope of the claims.

Claims

1. A manufacturing method of a two-dimensional sensor based on carbon nano tubes is characterized by comprising the following steps: the method comprises the following steps:

step 1: preparing carbon nanotubes by chemical vapor deposition;

step 1.1: 1nm iron/10 nm aluminum oxide placed on a silicon wafer is used as a catalyst, ethylene is used as a carbon source, a mixed gas of argon and hydrogen is used as a carrier gas, the ambient temperature of 750 ℃ is maintained, multi-wall carbon nano-tube CNT is formed on the surface of the catalyst, and a CNT array is synthesized on a quartz tube furnace through chemical vapor deposition;

step 2: sample preparation, including biaxial sample preparation;

the biaxial sample preparation comprises the following steps:

taking a piece of SEBS rubber, and respectively stretching the SEBS rubber in the transverse direction and the longitudinal direction by 4 times; and transversely placing a section of CNT sheet on the SEBS rubber, longitudinally placing a section of CNT sheet on the SEBS rubber, and superposing the two sections of CNT sheets in a mutually perpendicular mode to obtain the biaxial two-dimensional sensor with a fold structure, wherein the fold structure is formed by combining transverse folds and longitudinal folds.