Multi-layer regulation and control amorphous carbon film for flexible piezoresistive sensing and preparation method of multi-layer regulation and control amorphous carbon film

Abstract

A multilayer regulation amorphous carbon film for flexible piezoresistive sensing comprises a flexible substrate, the flexible substrate is provided with an amorphous carbon film, the amorphous carbon film is formed by alternately overlapping sp2-rich hybrid carbon layers and sp3-rich hybrid carbon layers, the thickness of each sp2-rich hybrid carbon layer and the thickness of each sp3-rich hybrid carbon layer are 50-150 nm, the thickness of each sp3-rich hybrid carbon layer is 50-150 nm, and the thickness of each sp2-rich hybrid carbon layer and the thickness of each sp3-rich hybrid carbon layer are 50-150 nm. And the total thickness of the amorphous carbon film formed by alternately overlapping the sp2-rich hybrid carbon layer and the sp3-rich hybrid carbon layer is 400-500 nm. A metal doping layer or a metal intermediate layer does not need to be introduced, the interface bonding force, the structural compactness and the mechanical flexibility are remarkably improved, and the piezoresistive sensitivity and the environmental stability are optimized. The amorphous carbon film is particularly suitable for flexible electronic skin, wearable equipment and other scenes, and has industrial feasibility.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible electronic materials, in particular to a multilayer regulated amorphous carbon film for flexible piezoresistive sensing and a preparation method thereof. BACKGROUND

[0002] Amorphous carbon film is a low-cost, high-performance pressure-sensitive material. The rich sp 2 hybridization in the structure of amorphous carbon film endows it with high piezoresistive sensitivity, corrosion resistance and scratch resistance. Amorphous carbon film has various morphologies and is easy to prepare. The piezoresistive effect of amorphous carbon film mainly comes from the dynamic change of sp 3 hybridized carbon conductive network caused by external mechanical stress, which has great application potential in the field of flexible piezoresistive sensing. 2 Generally, the carbon atoms in amorphous carbon film are mainly connected by sp 2 hybridization and sp 3 hybridization to form irregular space network structures, so that amorphous carbon film has both sp 3 and sp 2 hybridization of two carbon atoms, wherein sp 3 hybridization makes the material harder and more chemically inert, and sp 2 hybridization forms a conductive network, making the material conductive.

[0003] Currently, common preparation processes of amorphous carbon film include ion beam assisted deposition (IBAD) and direct current magnetron sputtering deposition (DCMS). These methods have problems such as loose film layer, high internal stress, poor adhesion, etc. caused by insufficient ion energy. Moreover, these methods are difficult to directly prepare high-quality amorphous carbon film on a flexible substrate. If amorphous carbon film is directly deposited on a flexible substrate, high internal stress and mechanical mismatch with the substrate can easily induce wrinkles and cracks, making it difficult to control the conductive performance and strain response mechanism. Therefore, the existing methods basically deposit amorphous carbon film on a rigid substrate, then dissolve the rigid substrate by chemical method, retain the amorphous carbon film (amorphous carbon film is corrosion-resistant and very stable), and then transfer the amorphous carbon film to a flexible substrate and bond it with the flexible substrate. However, there are problems of film layer damage and interface adhesion reduction in the process of transferring amorphous carbon film. To solve these problems, the existing technology usually locally improves adhesion by metal doping or introducing a metal intermediate layer, but metal doping or introducing a metal intermediate layer can increase the interface instability and thermal expansion mismatch problem, affecting long-term stability.

[0004] In the invention patent with the authorization announcement number CN114440757B, an amorphous carbon film material is prepared by optimizing three core process parameters of substrate pulse bias, gas flow and sputtering power under the condition of direct current magnetron sputtering. The carbon film is controlled through complex regulation of the three process parameters to have different stress and initial resistance characteristics. However, the change of the sp 2 , sp 3 content in the amorphous carbon film is realized by changing multiple process parameters, the irregular space network structure formed by sp 2 hybridization and sp 3 hybridization is still irregular, and the process is complex and requires a large number of verification experiments as a development basis. SUMMARY

[0005] The present application provides a multi-layer regulated amorphous carbon film for flexible piezoresistive sensing, which avoids the problems of interface instability and thermal expansion failure caused by setting metal doping or metal intermediate layer in the traditional way by regulating the hybridization of carbon bonds at different levels. The response sensitivity, linearity and environmental stability of the piezoresistive effect are optimized, and it is particularly suitable for the sensitive layer material requirements of flexible electronic skin, wearable devices and flexible sensors, and has excellent preparation controllability, industrial adaptability and long-term service stability.

[0006] The present application also provides a preparation method of a multi-layer regulated amorphous carbon film for flexible piezoresistive sensing. The amorphous carbon film is prepared by a high-power pulsed magnetron sputtering method. By adjusting the process parameters of the ion beam composite magnetron sputtering coating deposition equipment during the preparation of the amorphous carbon film, a multi-layer all-carbon structure amorphous carbon film is accurately constructed on the flexible substrate, and an alternating layered design of sp 2 hybridization-rich carbon layer and sp 3 hybridization-rich carbon layer is formed, so that the amorphous carbon film forms a tunable conductive network and mechanical support distribution. The problems of interface instability and thermal expansion failure caused by introducing metal doping or intermediate metal layer in the traditional way are avoided.

[0007] The technical scheme of the present application is: a multi-layer regulated amorphous carbon film for flexible piezoresistive sensing, comprising a flexible substrate, an amorphous carbon film disposed on the flexible substrate, the amorphous carbon film being formed by alternating overlapping of sp 2 hybridization-rich carbon layers and sp 3 hybridization-rich carbon layers, each sp 2 hybridization-rich carbon layer and each sp 3 hybridization-rich carbon layer having a layer thickness of 50-150nm, so that the amorphous carbon film formed by the sp 2 hybridization-rich carbon layers and the sp 3The total thickness of the amorphous carbon film formed by the alternating overlapping of hybrid carbon layers is 400–500 nm.

[0008] Preferably, the flexible matrix is ​​formed from any one or more combinations of polydimethylsiloxane, polyvinylidene fluoride, polyethylene terephthalate, polypropylene, polyimide, polymethyl methacrylate, natural rubber, styrene-butadiene rubber, epoxy resin, Ecoflex, and thermoplastic elastomers.

[0009] A method for preparing a multilayer modulated amorphous carbon thin film for flexible piezoresistive sensing includes the following steps:

[0010] 1) Install a high-purity graphite target on the planar sputtering cathode of the ion beam composite magnetron sputtering coating deposition equipment, and fix the cleaned flexible substrate on the sample holder in the vacuum chamber of the ion beam composite magnetron sputtering coating deposition equipment;

[0011] 2) Close the vacuum chamber door and evacuate until the vacuum level in the vacuum chamber reaches 5×10⁻⁶. -4 Pa;

[0012] 3) The sample holder is rotated to the front of the ion source through the orbital suspension of the vacuum chamber, oxygen is introduced, the ion source current is set to 1A, and the ion source voltage is maintained at 1200V by dynamically adjusting the oxygen flow rate, and the substrate DC bias voltage is -500V. The flexible substrate is etched. During the etching process, the sample holder rotates at 30rpm and the etching takes 20 minutes.

[0013] 4) After etching, turn off the ion source, rotate the sample holder to the front of the graphite target, and use a high-power pulsed magnetron sputtering deposition method. By adjusting the process parameters, alternately overlapping sp-rich deposits are formed on the flexible substrate surface. 2 Hybrid carbon layers and sp-rich 3 Hybridized carbon layers form a multilayered amorphous carbon thin film.

[0014] Preferably, in step 1), the flexible substrate is ultrasonically cleaned in deionized water and anhydrous ethanol for 15 minutes in sequence.

[0015] Preferably, in step 2), the mechanical pump and molecular pump of the ion beam composite magnetron sputtering coating deposition equipment are turned on in sequence to perform vacuuming.

[0016] Preferably, in step 3), the oxygen flow rate is 28–45 sccm.

[0017] Preferably, in step 4), the deposit is rich in sp. 2 When constructing the hybrid carbon layer, the process parameters of the ion beam composite magnetron sputtering coating deposition equipment are adjusted as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40~70sccm, chamber gas pressure maintained: 1×10 -2Pa, input signal duty cycle: 10%~15%, pulse width: 100us, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20~30min, and the target power density is 1kW / cm by adjusting the target power 2 .

[0018] Preferably, in step 4), the sp 3 hybrid carbon layer is deposited by adjusting the process parameters of the ion beam composite magnetron sputtering coating deposition device as follows: substrate direct current bias: -100V, cavity inlet argon: 40~70sccm, cavity gas pressure: 1x10 -2 Pa, input signal duty cycle: 2%~5%, pulse width: 100us, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20~30min, and the target power density is 3kW / cm by adjusting the target power 2 .

[0019] Preferably, each layer of sp 2 hybrid carbon layer is rich. 3 The thickness of the sp 3 hybrid carbon layer is the same.

[0020] Preferably, the amorphous carbon thin film is at least a four-layer structure.

[0021] The advantages of the present application are:

[0022] 1) The amorphous carbon thin film structure of the present application avoids the problems of interface instability and thermal expansion failure caused by the introduction of metal doping or intermediate metal layers, and improves the interface bonding strength and service stability.

[0023] 2) The present application uses a high-power pulsed magnetron sputtering deposition method, which can continuously and stably control the ratio of sp 2 , sp 3 in the amorphous carbon thin film by adjusting the input signal duty cycle and target power in the ion beam composite magnetron sputtering coating deposition device, simplifying the process flow and reducing production costs.

[0024] 3) The amorphous carbon thin film of the present application is a multi-layer regulated structure of alternating sp 2 hybrid carbon layer, sp 3 hybrid carbon layer, which takes into account high sensitivity, wide range, good linearity and mechanical flexibility, ensuring its stable operation in a complex deformation environment.

[0025] 4) The preparation method of the present application can be directly deposited on a flexible substrate at low temperature without the need for intermediate transfer process, significantly improving the reliability and consistency of flexible devices.

[0026] 5) The high-power pulsed magnetron sputtering deposition method adopted in the present application has excellent repeatability and a wide process window, and can be extended to roll-to-roll continuous production, meeting the needs of industrialization and amplification.

[0027] 6) The amorphous carbon film of the present application has good corrosion resistance and scratch resistance, and is suitable for various flexible electronic, wearable sensing and electronic skin applications, and has wide commercial prospects. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a structural schematic diagram of the present application;

[0029] Figure 2 is a front view (a) and a top view (b) of the arrangement of the target material, ion source and sample holder in the vacuum chamber when preparing an amorphous carbon film by high-power pulsed magnetron sputtering in the present application;

[0030] Figure 3 is a structural comparison schematic diagram of examples 1 and 2 of the present application,

[0031] Figure 4 is a schematic diagram of the amorphous carbon film on the PDMS substrate in an embodiment of the present application;

[0032] Figure 5 is the C1s test spectrum of the amorphous carbon film of example 1 and example 2 in the present application;

[0033] Figure 6 is a diagram showing the sp 2 , sp 3 proportion of different layers of amorphous carbon film in the alternating multilayer structure in the present application. DETAILED DESCRIPTION

[0034] Referring to Figure 1 , a multilayer regulated amorphous carbon film for flexible piezoresistive sensing includes a flexible substrate, and an amorphous carbon film disposed on the flexible substrate, the amorphous carbon film being formed by alternating and overlapping sp 2 -rich hybrid carbon layers and sp 3 -rich hybrid carbon layers, each sp 2 -rich hybrid carbon layer and each sp 3 -rich hybrid carbon layer having a layer thickness of 50-150 nm, so that the sp 2 -rich hybrid carbon layers and the sp 3The total thickness of the amorphous carbon film formed by alternating overlapping hybrid carbon layers is 400–500 nm. The flexible substrate is formed from any one or more combinations of polydimethylsiloxane, polyvinylidene fluoride, polyethylene terephthalate, polypropylene, polyimide, polymethyl methacrylate, natural rubber, styrene-butadiene rubber, epoxy resin, Ecoflex (biodegradable plastic), and thermoplastic elastomers, and is not limited thereto.

[0035] A method for preparing a multilayer modulated amorphous carbon thin film for flexible piezoresistive sensing includes the following steps:

[0036] 1) The flexible substrate was ultrasonically cleaned in deionized water and anhydrous ethanol for 15 minutes in sequence to remove oil and other reabsorbed impurities from its surface. After cleaning, the surface residual liquid was dried with a hair dryer and then placed in a vacuum bag for later use.

[0037] See Figure 2 A high-purity graphite target is installed on the planar sputtering cathode of the ion beam composite magnetron sputtering coating deposition equipment, and the cleaned flexible substrate is fixed on the sample holder in the vacuum chamber of the ion beam composite magnetron sputtering coating deposition equipment.

[0038] 2) Close the vacuum chamber door and evacuate. Then, sequentially turn on the mechanical pump and molecular pump of the ion beam composite magnetron sputtering coating deposition equipment to evacuate until the vacuum level in the vacuum chamber reaches 5 × 10⁻⁶. -4 Pa;

[0039] 3) The sample holder is rotated to the front of the ion source via the orbital suspension of the vacuum chamber. Oxygen is introduced and the ion source current is set to 1A. The ion source voltage is maintained at 1200V and the substrate DC bias voltage is -500V by dynamically adjusting the oxygen flow rate. The flexible substrate is etched. During the etching process, the sample holder rotates at 30rpm and the etching takes 20 minutes. The oxygen flow rate is 28-45sccm.

[0040] 4) After etching, turn off the ion source, rotate the sample holder to the front of the graphite target, and use a high-power pulsed magnetron sputtering deposition method. By adjusting the process parameters, alternately overlapping sp-rich deposits are formed on the flexible substrate surface. 2 Hybrid carbon layers and sp-rich 3 Hybrid carbon layers, each rich in sp. 2 Hybrid carbon layers and sp-rich 3 The hybrid carbon layers are of equal thickness, forming an amorphous carbon thin film with at least four layers.

[0041] Deposits rich in sp 2 When constructing the hybrid carbon layer, the process parameters of the ion beam composite magnetron sputtering coating deposition equipment are adjusted as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40~70sccm, chamber gas pressure maintained: 1×10-2 Pa, input signal duty cycle: 10%~15%, pulse width: 100μs, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20~30 minutes, and the target power density is 1kW / cm by adjusting the target power 2 .

[0042] sp 3 rich hybrid carbon layer, the process parameters of the ion beam composite magnetron sputtering coating deposition device are adjusted as follows: substrate direct current bias: -100V, argon gas inlet: 40~70sccm, cavity gas pressure: 1×10 -2 Pa, input signal duty cycle: 2%~5%, pulse width: 100μs, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20~30 minutes, and the target power density is 3kW / cm by adjusting the target power 2 .

[0043] Example 1: Preparation of a four-layer amorphous carbon film structure with a sp 3 rich hybrid carbon layer as the outermost layer

[0044] 1) A flexible substrate made of polydimethylsiloxane with a size of 100mm×130mm×1mm is ultrasonically cleaned in deionized water and anhydrous ethanol for 15 minutes, respectively. After cleaning, the surface of the flexible substrate is dried by a hair dryer and then packaged in a vacuum bag for use;

[0045] 2) A high-purity graphite target is installed on the planar sputtering cathode of the ion beam composite magnetron sputtering coating deposition device, and the cleaned flexible substrate is fixed on the sample holder in the vacuum chamber of the ion beam composite magnetron sputtering coating deposition device;

[0046] 3) Close the vacuum chamber door and evacuate, and then sequentially start the mechanical pump and molecular pump of the ion beam composite magnetron sputtering coating deposition device for evacuation until the vacuum degree of the vacuum chamber reaches 5×10 -4 Pa;

[0047] 4) Rotate the sample holder to the front of the ion source through the revolution suspension of the vacuum chamber, introduce oxygen, set the ion source current to 1A, and dynamically adjust the oxygen flow to maintain the ion source voltage at 1200V, and the substrate direct current bias at -500V. Etch the flexible substrate, and the sample holder rotates at 30rpm at the same time during the etching process. Etch for 20 minutes; wherein the oxygen flow is 28~45sccm.

[0048] 5) After etching, turn off the ion source and rotate the sample holder to the front of the graphite target. Using a high-power pulsed magnetron sputtering deposition method, adjust the process parameters of the ion beam composite magnetron sputtering coating deposition equipment as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40 sccm, chamber pressure maintained: 1×10⁻⁶. -2 Pa, target power: 1500W, input signal duty cycle: 10%, pulse width: 100μs, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20 minutes, to deposit a sp-rich layer with a thickness of approximately 100nm on the surface of the flexible material. 2 A hybrid carbon layer serves as the first layer;

[0049] 6) Adjust the process parameters of the ion beam composite magnetron sputtering coating deposition equipment as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40 sccm, chamber gas pressure maintained: 1×10 -2 Pa, target power: 4000W, input signal duty cycle: 2%, pulse width: 100μs, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20 minutes, to enrich the surface of the flexible material with sp. 2 A layer of sp2-rich material with a thickness of approximately 100 nm was deposited on the hybrid carbon layer. 3 A hybrid carbon layer serves as the second layer;

[0050] 7) Adjust the process parameters of the ion beam composite magnetron sputtering coating deposition equipment as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40 sccm, chamber gas pressure maintained: 1×10 -2 Pa, target power: 1500W, input signal duty cycle: 10%, pulse width: 100μs, frequency: 200Hz, target voltage: -710V, sputtering current: 2.7A, sample holder rotation speed: 30rpm, deposition time: 20 minutes, to deposit a sp-rich layer with a thickness of approximately 100nm on the second layer of the flexible material surface. 2 A hybrid carbon layer serves as the third layer;

[0051] 8) Adjust the process parameters of the ion beam composite magnetron sputtering coating deposition equipment as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40 sccm, chamber gas pressure maintained: 1×10 -2Pa, target power: 4000 W, input signal duty cycle: 2%, pulse width: 100 μs, frequency: 200 Hz, target voltage: -710 V, sputtering current: 2.7 A, sample holder rotation speed: 30 rpm, deposition time: 20 minutes, to deposit a layer of sp 3 hybrid carbon layer on the third layer of the flexible material surface, with a thickness of about 100 nm. 3 The fourth layer of the four-layer amorphous carbon film structure is an sp Figure 3 rich hybrid carbon layer.

[0052] Example 2: Preparation of a four-layer amorphous carbon film structure with the outermost layer being an sp 2 rich hybrid carbon layer

[0053] 1) A flexible substrate made of polydimethylsiloxane with a size of 100 mm x 130 mm x 1 mm was ultrasonically cleaned in deionized water and anhydrous ethanol for 15 minutes, respectively. After cleaning, the flexible substrate surface was dried by a hair dryer and then packaged in a vacuum bag for use.

[0054] 2) A high-purity graphite target was installed on the planar sputtering cathode of the ion beam composite magnetron sputtering coating deposition equipment, and the cleaned flexible substrate was fixed on the sample holder in the vacuum chamber of the ion beam composite magnetron sputtering coating deposition equipment.

[0055] 3) Close the vacuum chamber door and evacuate, then start the mechanical pump and molecular pump of the ion beam composite magnetron sputtering coating deposition equipment for evacuation, until the vacuum degree of the vacuum chamber reaches 5 x 10 -4 Pa.

[0056] 4) Rotate the sample holder to the front of the ion source through the revolution suspension of the vacuum chamber, introduce oxygen, set the ion source current to 1 A, and maintain the ion source voltage at 1200 V by dynamically adjusting the oxygen flow. The substrate DC bias is -500 V. Etch the flexible substrate. During the etching process, the sample holder rotates at 30 rpm. Etch for 20 minutes. The oxygen flow rate is 28-45 sccm.

[0057] 5) After etching, turn off the ion source, rotate the sample holder to the front of the graphite target, and use high-power pulsed magnetron sputtering deposition method. Adjust the process parameters of the ion beam composite magnetron sputtering coating deposition equipment as follows: substrate DC bias: -100 V, cavity argon gas flow: 40 sccm, cavity gas pressure: 1 x 10 -2A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 3 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer.

[0058] 6) The process parameters of the ion beam composite magnetron sputtering coating deposition device are adjusted as follows: substrate direct current bias: -100 V, cavity connected to argon gas: 40 sccm, cavity gas pressure: 1 x 10 -2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 3 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer.

[0059] 7) The process parameters of the ion beam composite magnetron sputtering coating deposition device are adjusted as follows: substrate direct current bias: -100 V, cavity connected to argon gas: 40 sccm, cavity gas pressure: 1 x 10 -2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 3 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer.

[0060] 8) The process parameters of the ion beam composite magnetron sputtering coating deposition device are adjusted as follows: substrate direct current bias: -100 V, cavity connected to argon gas: 40 sccm, cavity gas pressure: 1 x 10 -2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. 2 A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer. Figure 3 ).

[0061] A sp3-rich carbon layer with a thickness of about 100 nm is deposited on the surface of the flexible material as the first layer.Figure 4 For the actual figure of the multilayer amorphous carbon film prepared on the PDMS substrate by the preparation method of the present application, the film has no peeling and cracking phenomenon, and has good bonding stability with the PDMS substrate material.

[0062] Referring to Figure 5 For the XPS test C1s test spectrum of the outermost layer of the four-layer amorphous carbon film prepared in Example 1 and Example 2, it is fitted and analyzed according to sp 2 , sp 3 and C-O, and it can be seen that the outermost layer prepared in Example 1 is a four-layer amorphous carbon film structure rich in sp 3 hybrid carbon layer, and the carbon bond peak area of sp 3 is obviously larger than that of sp 2 , and sp 3 is dominant; the outermost layer prepared in Example 2 is a four-layer amorphous carbon film structure rich in sp 2 hybrid carbon layer, and the carbon bond peak area of sp 2 is obviously larger than that of sp 3 , and sp 2 is dominant. The test results clearly show that the controllable adjustment of sp 2 , sp 3 carbon bond components in the amorphous carbon film can be realized, and the control of the film stress and resistance is realized.

[0063] Referring to Figure 6 For the carbon bond proportion quantitative test results of the four-layer amorphous carbon film prepared in Example 1 and Example 2, through fitting and quantitative analysis of the XPS test spectrum, it is found that in the four-layer amorphous carbon film structure rich in sp 3 hybrid carbon layer in the outermost layer prepared in Example 1, the proportion of sp 3 hybrid carbon reaches 69%, and in the four-layer amorphous carbon film structure rich in sp 2 hybrid carbon layer in the outermost layer prepared in Example 2, the proportion of sp 2 hybrid carbon reaches 46%, realizing the controllable design and preparation of different carbon bond components in the amorphous carbon film.

[0064] The initial resistance of the amorphous carbon film of Example 1 and Example 2 is tested by the four-probe method, and the results are shown in Table 1.

[0065] Sample Example 1 Example 2 Initial resistance 1.43 MΩ 1.21 MΩ 1.43 MΩ 1.21 MΩ

[0066] Table 1

[0067] From Table 1, it can be seen that the more sp 3 hybrid carbon, the greater the initial resistance of the amorphous carbon film, and the more sp 2The more the hybrid carbon is, the smaller the initial resistance of the amorphous carbon film is, so that the sp 3 hybrid carbon, sp 2 The regulation of the hybrid carbon, for example, needs to reduce the initial resistance of the amorphous carbon film, and the sp 2 hybrid carbon layer, needs to increase the initial resistance of the amorphous carbon film, and the sp 3 hybrid carbon layer, so as to realize the regulation of the initial resistance of the amorphous carbon film and the on-demand design of the amorphous carbon film.

[0068] It is understood that the above embodiments are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For ordinary skilled in the art to which the present application belongs, without departing from the concept of the present application, some simple deductions or substitutions can be made, and any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A multilayer regulated amorphous carbon thin film for flexible piezoresistive sensing, characterized by: A flexible substrate having an amorphous carbon film formed thereon, the amorphous carbon film being formed by alternately stacking sp 2 hybrid carbon layers and sp 3 enriched carbon layers, the amorphous carbon film having a total thickness of 400 to 500 nm. 2 hybrid carbon layers and sp 3 enriched carbon layers, the amorphous carbon film having a total thickness of 400 to 500 nm. 2 hybrid carbon layers and sp 3 enriched carbon layers, the amorphous carbon film having a total thickness of 400 to 500 nm.

2. The multilayer regulated amorphous carbon film for flexible piezoresistive sensing of claim 1, wherein: The flexible substrate is formed of any one or more combinations of polydimethylsiloxane, polyvinylidene fluoride, polyethylene terephthalate, polypropylene, polyimide, polymethyl methacrylate, natural rubber, styrene butadiene rubber, epoxy resin, Ecoflex, and thermoplastic elastomer.

3. A method for the preparation of a multilayer regulated amorphous carbon film for flexible piezoresistive sensing according to claim 1 or 2, characterized in that, The method comprises the following steps: 1) mounting a high-purity graphite target on a planar sputtering cathode of an ion beam composite magnetron sputtering coating deposition device, and fixing a cleaned flexible substrate on a sample holder in a vacuum chamber of the ion beam composite magnetron sputtering coating deposition device; 2) Close the vacuum chamber door and evacuate until the vacuum chamber reaches a vacuum of 5 x 10 -4 Pa; 3) rotating the sample holder to the front of the ion source through a revolution suspension of the vacuum chamber, introducing oxygen, setting the ion source current to 1 A, maintaining the ion source voltage at 1200 V by dynamically adjusting the oxygen flow, setting the substrate direct current bias to -500 V, etching the flexible substrate, and rotating the sample holder at 30 rpm during the etching process for 20 minutes; 4) After etching, turn off the ion source, and rotate the sample holder to the front of the graphite target. Using high-power pulsed magnetron sputtering deposition method, by adjusting the process parameters, the flexible substrate surface is deposited with alternating overlapping sp 2 hybrid carbon layer and sp 3 hybrid carbon layer, forming a multilayer structure of amorphous carbon film.

4. The method of claim 3, wherein: In step 1), the flexible substrate is sequentially ultrasonically cleaned in deionized water and anhydrous ethanol for 15 minutes.

5. The method of claim 3, wherein: In step 2), a mechanical pump and a molecular pump of the ion beam composite magnetron sputtering coating deposition device are sequentially started to perform vacuum pumping.

6. The method of claim 3, wherein: In step 3), the oxygen flow is 28-45 sccm.

7. The method of claim 3, wherein: In step 4), the sediment is rich in sp. 2 When constructing the hybrid carbon layer, the process parameters of the ion beam composite magnetron sputtering coating deposition equipment are adjusted as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40~70sccm, chamber gas pressure maintained: 1×10 -2 Pa, input signal duty cycle: 10%–15%, pulse width: 100 μs, frequency: 200 Hz, target voltage: -710 V, sputtering current: 2.7 A, sample holder rotation speed: 30 rpm, deposition time: 20–30 minutes, and the target power density is adjusted to 1 kW / cm³. 2 .

8. The method of claim 3, wherein: In step 4), the sediment is rich in sp. 3 When constructing the hybrid carbon layer, the process parameters of the ion beam composite magnetron sputtering coating deposition equipment are adjusted as follows: substrate DC bias: -100V, argon gas introduced into the chamber: 40~70sccm, chamber gas pressure maintained: 1×10 -2 Pa, input signal duty cycle: 2%–5%, pulse width: 100 μs, frequency: 200 Hz, target voltage: -710 V, sputtering current: 2.7 A, sample holder rotation speed: 30 rpm, deposition time: 20–30 minutes, and the target power density is adjusted to 3 kW / cm². 2 .

9. The method of claim 3, wherein: Each layer is rich in sp 2 The hybrid carbon layer and the sp 3 The thickness of the hybrid carbon layer is the same.

10. The method of claim 3, wherein: The amorphous carbon thin film is at least a four-layer structure.

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