Humidity-strain dual-response amorphous carbon-based flexible sensor and preparation method thereof

Abstract

The invention relates to the technical field of flexible sensors, and provides a humidity and strain dual-response amorphous carbon-based flexible sensor and a preparation method thereof, the flexible sensor comprises a flexible substrate, a sensing sensitive layer arranged on the flexible substrate, and a sensing electrode electrically connected with the sensing sensitive layer; wherein the sensing sensitive layer is an amorphous carbon film and is used for collecting external signals and transmitting the signals through the sensing electrodes, the strain sensing range epsilon of the humidity and strain dual-response amorphous carbon-based flexible sensor is larger than 0 and smaller than 210%, and the humidity sensing range is 45%-95% RH. The sensor is easy and simple to prepare, can give consideration to high sensitivity and wide sensing range, has good stability and reversibility in the aspects of strain and humidity response, and can be applied to the fields of intelligent wearing, health detection and the like.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to a humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method. Background Technology

[0002] Flexible sensors, as emerging intelligent devices, are mainly formed by integrating sensitive units on flexible substrates, possessing characteristics such as flexibility, lightweight, and high sensitivity. With the surge in demand from the Internet of Things, wearable devices, and healthcare fields, they are widely used in scenarios such as electronic skin, motion monitoring, and human-computer interaction. In particular, relying on breakthroughs in materials science and micro-nano manufacturing technologies, they are accelerating their transition from the laboratory to industrialization, becoming a core technological support for the sensing layer in the era of the Internet of Everything.

[0003] With the rapid development of wearable devices, smart health electronic products, and mobile healthcare applications, sensing technologies such as real-time acquisition, wireless transmission, and precise identification of multi-parameter information have become important development directions. Currently, integrating multiple sensors is one of the main ways to achieve multi-parameter and modal information sensing. However, multifunctional sensor systems have different sizes, shape parameters, detection principles, signal types, and acquisition methods for each sensing unit, making sensor integration and data processing difficult. In particular, most existing humidity sensors are usually incompatible with flexible substrates (or substrates) and rely on traditional inorganic rigid materials and complex manufacturing processes, making it difficult to develop flexible strain and multi-parameter humidity sensors.

[0004] Existing amorphous carbon-based flexible sensors primarily utilize the difference in mechanical properties between amorphous carbon and flexible substrates to create cracks and wrinkles, enabling efficient sensing of varying strains. Furthermore, the surface cracks, wrinkles, and conductive junctions—these micro- and nano-textures—can alter surface wetting behavior and conductivity, thus affecting the sensor's electrical performance and sensitivity under different strain and humidity conditions. However, the high internal stress of the amorphous carbon film leads to highly random and disordered wrinkle morphology and microstructure on the flexible substrate surface, significantly reducing device conductivity. Achieving ordered and regular fabrication of the amorphous carbon film's micro-sensitive structure, along with excellent electrical performance, is one of the key challenges in fabricating humidity-strain dual-response amorphous carbon-based flexible sensors. Summary of the Invention

[0005] This invention provides a humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method to address the shortcomings of existing flexible sensors.

[0006] To achieve the above objectives, the present invention provides a humidity-strain dual-response amorphous carbon-based flexible sensor, comprising a flexible substrate, a sensing layer disposed on the flexible substrate, and a sensing electrode electrically connected to the sensing layer; wherein, The sensing layer is an amorphous carbon film, used to collect external signals and transmit them through the sensing electrodes. The strain sensing range of the humidity-strain dual-response amorphous carbon-based flexible sensor is 0 < ε < 210%, and the humidity sensing range is 45% to 95% RH.

[0007] In addition, an optional technical solution is that the strain sensing range is 80% < ε < 210%, and the humidity sensing range is 35% ~ 45%RH.

[0008] In addition, an optional technical solution is that the thickness of the sensing layer ranges from 60 to 1500 nm.

[0009] Furthermore, an optional technical solution is that the flexible matrix material includes elastomers and polymers; wherein, The elastomer includes at least one of butyl rubber, natural rubber, and Ecoflex. The polymer includes at least one of polydimethylsiloxane, polyimide, polyester, and thermoplastic polyurethane.

[0010] On the other hand, the present invention also provides a method for fabricating a humidity-strain dual-response amorphous carbon-based flexible sensor, used to fabricate the aforementioned humidity-strain dual-response amorphous carbon-based flexible sensor; the method includes: A flexible substrate is obtained, and the flexible substrate is pretreated using plasma modification technology to obtain a non-damaging micro / nano structure flexible substrate; A graphite target is sputtered using DC magnetron sputtering technology to deposit an amorphous carbon film on the surface of the micro / nano structure flexible substrate, forming a sensing layer. Sensing electrodes are attached to both ends of the sensing layer to form the humidity-strain dual-response amorphous carbon-based flexible sensor.

[0011] In addition, an optional technical solution is that the acquisition of a non-damaging micro-nano structure flexible substrate includes: placing the flexible substrate in the chamber of a plasma processing device, growing a metal mask on the surface, and performing a vacuum operation. When the vacuum level of the chamber of the plasma processing equipment reaches 1×10 -5 ~3×10 -5 After the Torr is introduced, the target gas is introduced, and the gas is ionized by the radio frequency power supply to obtain plasma; Based on the region selectivity of the metal mask, the flexible substrate is subjected to plasma modification to obtain the micro / nano structure flexible substrate.

[0012] In addition, an optional technical solution is that the material of the metal mask includes at least one of iron, aluminum, copper, and stainless steel; The metal mask has a planar structure, including any one or more combinations of circular, rectangular, rhomboid, elliptical, polygonal, strip, linear, mesh, and array shapes.

[0013] In addition, an optional technical solution is that the target gas includes argon, oxygen or nitrogen, and the flow rate of the target gas is 50~120 sccm; The working gas pressure of the plasma processing equipment chamber is 15~200mTorr, the working voltage is -500~-250V, the radio frequency power supply frequency is 350kHz, the pulse width is 1.1μs, and the modification time is 30s~10min.

[0014] In addition, an alternative technical solution is to deposit an amorphous carbon film on the surface of the micro / nano structure flexible substrate, including: After placing the micro / nano structured flexible substrate in the chamber of the magnetron sputtering equipment, a vacuum operation was performed, and when the vacuum level reached 8×10⁻⁶... -6 ~1×10 -5 Argon gas is introduced and an electric current is applied during the Torr process to sputter a graphite target with a purity of 99.9% to deposit an amorphous carbon film on the surface of the micro / nano structure flexible substrate.

[0015] In addition, an optional technical solution is that the micro-nano structure flexible substrate is placed on a rotating frame in the chamber of the magnetron sputtering equipment, and the rotation frequency range of the rotating frame is 100~120Hz; The working gas pressure of the magnetron sputtering equipment chamber is 2.5~3.2 mTorr, the sputtering current is 2.5~3A, the deposition temperature is 20~30℃, the sputtering time is 10~240min, and no bias voltage is applied.

[0016] Compared with the prior art, the humidity-strain dual-response amorphous carbon-based flexible sensor and its preparation method provided by the present invention have an amorphous carbon film as the sensing layer, a strain sensing range of 0 < ε < 210%, a humidity sensing range of 45% to 95%RH, and can have ultra-high sensitivity and wide sensing range. It has dual-function response sensing and high temperature resistance, can be attached to the surface of various products or equipment, and has high stability and reversibility.

[0017] To achieve the foregoing and related objectives, one or more aspects of the invention include the features which will be described in detail below and specifically pointed out in the claims. The following description and accompanying drawings illustrate certain exemplary aspects of the invention. However, these aspects indicate only a few of the various ways in which the principles of the invention can be used. Furthermore, the invention is intended to include all such aspects and their equivalents. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the humidity-strain dual-response amorphous carbon-based flexible sensor according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the fabrication method of a humidity-strain dual-response amorphous carbon-based flexible sensor according to an embodiment of the present invention. Figure 3 This is a SEM image of the humidity-strain dual-response amorphous carbon-based flexible sensor in Embodiment 1 of the present invention. Figure 4 The diagram shows the contact angle of deionized water with and without a mesh-like microstructure on the PDMS substrate in Example 1 of this invention. Figure 5 The graph shows the test results of sensor sensitivity and strain range in Embodiment 1 of the present invention; Figure 6 The diagram shows the dynamic response of the sensor in Embodiment 1 of the present invention at 45%-75%RH and the sensing stability at 95%RH. Figure 7 The graph shows the test results of the sensor's elongation at break and thermal decomposition temperature in Embodiment 1 of the present invention. Figure 8 This is a diagram illustrating the application of the sensor in human motion detection in Embodiment 1 of the present invention; Figure 9 The image shows the test results of the sensor surface morphology, sensitivity, and strain range in Embodiment 2 of the present invention. Figure 10 This is a graph showing the test results of the sensor surface morphology, sensitivity, and strain range in Embodiment 3 of the present invention; Figure 11 This is a graph showing the test results of the sensor sensitivity and strain range in Comparative Example 1 of this invention.

[0019] Figure reference numerals: 1. Flexible substrate; 2. Sensing layer; 3. Sensing electrode.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B; the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone.

[0022] In the embodiments of this application, unless otherwise stated, "multiple" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. Furthermore, to facilitate a clear description of the technical solutions of the embodiments of this application, the terms "first," "second," etc., are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first," "second," etc., do not limit the quantity or execution order, and that "first," "second," etc., do not necessarily imply differences.

[0023] In this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being better or more advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner to facilitate understanding.

[0024] In view of the shortcomings of existing technologies, this invention provides a humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method. This sensor features a unique design, utilizing plasma modification technology to obtain a non-destructive micro / nanostructure flexible substrate, combined with DC magnetron sputtering technology for sensor fabrication. Through the synergy of the micro / nanostructure and the amorphous carbon film, accurate measurement of humidity and strain signals is achieved. It can also be used as a wearable sensor for human motion and health monitoring. The sensor has a simple fabrication process, exhibits both high sensitivity and a wide sensing range in strain response, and high repeatability. In terms of humidity response, it demonstrates good stability and reversibility, showing potential applications in smart wearables and health monitoring.

[0025] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Figure 1 A schematic structure of a humidity-strain dual-response amorphous carbon-based flexible sensor according to an embodiment of the present invention is shown.

[0027] like Figure 1As shown, the humidity-strain dual-response amorphous carbon-based flexible sensor of this invention includes: a flexible substrate 1, a sensing layer 2 disposed on the flexible substrate 1, and a sensing electrode 3 electrically connected to the sensing layer 2; wherein, the sensing layer 2 is an amorphous carbon film, used to collect external signals and transmit signals through the sensing electrode 3, wherein the external signals include humidity and strain, etc., and the strain sensing range of the humidity-strain dual-response amorphous carbon-based flexible sensor is 0 < ε < 210%, and the humidity sensing range is 45%~95%RH.

[0028] The preferred strain sensing range is 0 < ε < 50%. When the ambient humidity is 35% to 45% RH, the sensitivity coefficient is 13325.45. In addition, the strain sensing range can also be set to 80% < ε < 210% and the humidity sensing range to 35% to 45% RH, so as to ensure the detection sensitivity while achieving dual response of humidity and strain.

[0029] Furthermore, the humidity-strain dual-response amorphous carbon-based flexible sensor of this invention has a temperature range of T < 280℃, exhibiting high temperature tolerance and is suitable for surface mounting applications in high-temperature scenarios.

[0030] In some optional embodiments, the thickness of the sensing layer 2 ranges from 60 to 1500 nm, and the flexible substrate 1 is made of elastomers and polymers; wherein, the elastomer includes at least one of butyl rubber, natural rubber and Ecoflex; the polymer includes at least one of polydimethylsiloxane, polyimide, polyester, thermoplastic polyurethane, etc., and the sensing electrode 3 can be a rectangular conductive copper foil. The specific placement and number of sensing electrodes are not limited to the specific structure shown in the figure, and the sensing electrodes can be flexibly set according to application requirements.

[0031] Corresponding to the above-mentioned humidity-strain dual-response amorphous carbon-based flexible sensor, the present invention also provides a method for preparing the humidity-strain dual-response amorphous carbon-based flexible sensor, for preparing the above-mentioned humidity-strain dual-response amorphous carbon-based flexible sensor.

[0032] Specifically, Figure 2 A schematic flow diagram of the fabrication method of a humidity-strain dual-response amorphous carbon-based flexible sensor according to an embodiment of the present invention is shown. Figure 2 As shown, the fabrication method of the humidity-strain dual-response amorphous carbon-based flexible sensor according to an embodiment of the present invention includes at least the following steps: S100: Obtain a flexible substrate and pretreat it using plasma modification technology to obtain a non-damaging micro / nano structure flexible substrate.

[0033] Step S100 further includes: S110: Place the flexible substrate in the cavity of the plasma processing equipment, grow a metal mask on the surface, and perform a vacuuming operation. S120: When the vacuum level of the plasma processing equipment chamber reaches 1×10 -5 ~3×10 -5 After the Torr is introduced, the target gas is introduced, and the gas is ionized by the radio frequency power supply to obtain plasma; S130: Based on the region selectivity of metal masks, plasma modification is performed on flexible substrates to obtain micro-nano structured flexible substrates.

[0034] The material of the metal mask may include at least one of iron, aluminum, copper, stainless steel, etc.; the metal mask adopts a planar structure, including any one or more combinations of circular, rectangular, rhomboid, elliptical, polygonal, strip, linear, mesh, and array shapes.

[0035] In addition, the target gas includes argon, oxygen or nitrogen, and the flow rate of the target gas is 50~120 sccm; the working pressure of the plasma processing equipment chamber is 15~200 mTorr, the working voltage is -500~-250V, the radio frequency power supply frequency is 350kHz, the pulse width is 1.1μs, and the modification time is 30s~10min.

[0036] S200: Utilizes DC magnetron sputtering technology to sputter graphite targets to deposit amorphous carbon films on the surface of a micro / nano structured flexible substrate, forming a sensing layer.

[0037] In this process, after placing the flexible micro / nano structure substrate in the chamber of the magnetron sputtering equipment, a vacuum operation is performed, and when the vacuum level reaches 8×10⁻⁶... -6 ~1×10 -5 Argon gas is introduced and an electric current is applied during the Torr process to sputter a graphite target with a purity of 99.9% to deposit an amorphous carbon film on the surface of a micro / nano structured flexible substrate.

[0038] Specifically, the flexible substrate of micro-nano structure can be placed on the rotating frame of the chamber of the magnetron sputtering equipment. The rotation frequency of the rotating frame is in the range of 100~120Hz. The working gas pressure of the chamber of the magnetron sputtering equipment is 2.5~3.2mTorr, the sputtering current is 2.5~3A, the deposition temperature is 20~30℃, the sputtering time is 10~240min, and no bias voltage is applied.

[0039] S300: Sensing electrodes are attached to both ends of the sensing layer to form a humidity-strain dual-response amorphous carbon-based flexible sensor.

[0040] The humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method provided by this invention are based on plasma modification treatment to obtain a non-damaging micro / nano-structured flexible substrate. Combined with a designable metal mask, it can realize the low-cost, rapid, and morphologically regular ordered microstructure fabrication. At the same time, the modification treatment does not affect the intrinsic properties of the flexible substrate, thereby further realizing the controllability of the sensor's sensitive morphology and thus optimizing the sensor's performance.

[0041] As can be seen, the humidity-strain dual-response amorphous carbon-based flexible sensor provided by this invention has a unique design. It utilizes DC magnetron sputtering technology to fabricate the sensor's carbon film sensitive layer. By adjusting the core process parameter of deposition vacuum, it effectively reduces the oxygen content of the amorphous carbon film impurities, thereby improving the electrical conductivity of the amorphous carbon film and obtaining an amorphous carbon sensitive layer with excellent electrical properties. The process control is simple, facilitating the large-area fabrication of highly conductive amorphous carbon films and improving the performance of amorphous carbon-based sensors. Through the synergy between the micro / nano-structured flexible substrate and the amorphous carbon film, accurate measurement of humidity and strain signals is achieved. Furthermore, it can be used as a wearable sensor in human motion detection.

[0042] Furthermore, based on the protective effect of the amorphous carbon film, the applicability of the sensor in high-temperature environments can be improved. Not only is the preparation process simple, but it also has high sensitivity and wide sensing range in terms of strain response, as well as high repeatability and good stability and reversibility in terms of humidity response. It has application potential in fields such as smart wearables and health monitoring.

[0043] As a specific example, the method for fabricating a humidity-strain dual-response amorphous carbon-based flexible sensor provided by the present invention may specifically include the following steps: Step 1: Select a flexible substrate (including polydimethylsiloxane) and place it in the chamber of the plasma processing equipment. Apply 1mm thick conductive tape to both sides of the flexible substrate and place a stainless steel wire mesh larger than the area of ​​the flexible substrate as a (metal) mask. The conductive tape here can control the surface spacing between the mask and the flexible substrate, thereby achieving flexible adjustment of the sensor's sensitive morphology without affecting the intrinsic performance of the flexible substrate.

[0044] Then, the plasma processing equipment chamber was shut down and a vacuum operation was performed. When the chamber vacuum reached 3 × 10⁻⁶... -5 After the Torr is applied, 100 sccm of oxygen is introduced, the working pressure is set to 20 mTorr, and the radio frequency power supply is set to -500V, frequency 350kHz and pulse width 1.1μs to generate oxygen plasma.

[0045] Step 2: Under the action of a metal mask, oxygen plasma selectively etches the surface of the flexible substrate for 10 minutes to achieve regional surface hardening treatment. The unmodified parts remain soft polydimethylsiloxane and exhibit the same mesh structure as the metal mask. The oxygen plasma in the chamber selectively modifies the surface of the flexible substrate for 10 minutes through a stainless steel wire mesh to achieve the preparation of regular micro-nano textures (micro-nano structures) on the surface of the flexible substrate. Step 3: Place the flexible substrate with regular micro / nano texture on a rotating gantry and place it in the deposition chamber of the magnetron sputtering equipment. Perform a vacuum operation until the vacuum in the magnetron sputtering equipment chamber reaches 1.0 × 10⁻⁶. -5 When the temperature is below Torr, argon gas is introduced.

[0046] Then, the rotation speed frequency of the rotating frame was set to 120Hz, the DC power supply was turned on, and a 3A current was applied to achieve sputtering of the graphite target.

[0047] Step 4: Adhere conductive copper foil to both ends of the sensing layer to complete the fabrication of the humidity-strain dual-response amorphous carbon-based flexible sensor.

[0048] In another aspect of the present invention, the application of the aforementioned humidity-strain dual-response amorphous carbon-based flexible sensor in the field of flexible sensors is also provided.

[0049] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0050] It should be noted that, unless otherwise specified, all experimental materials used in the following examples can be obtained from conventional biochemical reagent companies.

[0051] Example 1 This embodiment 1 provides a humidity-strain dual-response amorphous carbon-based flexible sensor, which consists of a PDMS (polydimethylsiloxane) matrix with micro-nano structure, an amorphous carbon film sensing layer, and a conductive copper foil sensing electrode.

[0052] The fabrication method of this humidity-strain dual-response amorphous carbon-based flexible sensor includes the following steps: (1) Place the PDMS substrate in the chamber. The substrate thickness is 200 μm, and the applicable temperature is -40℃ to 200℃. Place a 100-mesh stainless steel wire mesh as a metal mask on the surface of the flexible substrate. Perform a vacuum operation on the chamber. When the vacuum degree reaches 3×10 -5 During Torr, oxygen is introduced at a flow rate of 100 sccm and the working pressure in the chamber is set to 20 mTorr. (2) The RF power supply parameters were set to -500V, 350kHz and 1.1μs to generate oxygen plasma for selective surface modification of the PDMS substrate for 10min. (3) Remove the metal mask, attach the PDMS substrate with micro-nano texture to the rotating frame, and perform a vacuum operation on the chamber. When the vacuum degree reaches 1.0×10-5Torr, set the frame rotation speed frequency to 120Hz, introduce argon gas, set the working gas pressure of the chamber to 2.5mTorr, turn on the DC power supply to apply a 3A current to realize the sputtering of the graphite target, set the deposition time to 160min, do not apply pulse negative bias voltage, and the film thickness of the sensing layer is about 1μm; (4) The conductive copper foil is bonded to both ends of the sample obtained in the previous step as sensor electrodes to form a humidity-strain dual-response amorphous carbon-based flexible sensor.

[0053] Specifically, the sensor surface morphology prepared using a 100-mesh stainless steel wire mesh as a metal mask is as follows: Figure 3 As shown, the deposited amorphous carbon film possesses a regular, complete, and ordered mesh structure. The deionized water contact angle of amorphous carbon films with and without mesh microstructures on the PDMS substrate was tested, and the results are as follows: Figure 4 As shown, the introduction of the mesh-like microstructure transforms the hydrophobic amorphous carbon film into a hydrophilic one, thereby realizing the humidity sensing behavior of the amorphous carbon-based flexible sensor.

[0054] The strain sensing performance of the sensor prepared above was characterized. Figure 5 The test results show the sensor's sensitivity and strain range. The sensor has a sensitivity of up to 13325.54 within 50% of the strain range and a linear fit of up to 0.998, achieving a synergy between high sensitivity and wide sensing range.

[0055] The humidity sensing performance of the sensor prepared above was characterized. Figure 6 Figures a and 6b show the dynamic response of the sensor in the range of 45%-75%RH and its sensing stability in the range of 95%RH. Using 45%RH as the baseline humidity, it was found that the device's response voltage gradually increases with the increase of relative humidity, and maintains a relatively stable voltage change in the range of 95%RH. Moreover, the waveform of the response voltage signal has good consistency, indicating that the sensor has good stability and reversibility, demonstrating the device's potential for humidity sensing applications.

[0056] The sensor was subjected to ultimate tensile testing and thermogravimetric testing. Figure 7The results of its elongation at break and thermal decomposition temperature tests are shown. The elongation at break of the amorphous carbon-based flexible sensor is 210%, indicating that the PDMS flexible substrate still has good deformation capacity after modification and amorphous carbon film deposition, and can perform strain detection exceeding 200%. The thermal decomposition temperature of the amorphous carbon-based flexible sensor is approximately 280℃, indicating that the sensor can withstand high temperatures up to 280℃. The applicable temperature range of the PDMS substrate is -40 to 200℃, demonstrating that the amorphous carbon film deposition enhances the temperature range of the PDMS flexible substrate, providing a certain degree of protection and offering a reference for the development of flexible sensors for extreme environments.

[0057] In addition, to explore the practical applications of the sensor, it was attached parallel to the finger in a natural state. Figure 8 The study demonstrated the real-time electrical signal changes in response to repeated finger bending. The results showed that the sensor's resistance increased as the finger bent and decreased rapidly as the finger extended, demonstrating the sensor's potential for human motion detection.

[0058] Example 2 This embodiment 2 provides a humidity-strain dual-response amorphous carbon-based flexible sensor, which consists of a PDMS substrate with micro-nano structure, an amorphous carbon film sensing layer, and a conductive copper foil sensing electrode.

[0059] The fabrication method of this humidity-strain dual-response amorphous carbon-based flexible sensor includes the following steps: (1) Place the PDMS substrate in the chamber. The substrate thickness is 200 μm, and the applicable temperature is -40℃ to 200℃. Place a 200-mesh stainless steel wire mesh on the substrate surface as a metal mask. Perform a vacuum operation on the chamber. When the vacuum degree reaches 3×10 -5 During Torr, oxygen is introduced at a flow rate of 100 sccm and the working pressure in the chamber is set to 20 mTorr. (2) The RF power supply parameters were set to -500V, 350kHz and 1.1μs to generate oxygen plasma for selective surface modification of the PDMS substrate for 10min. (3) Remove the metal mask, attach the PDMS substrate with micro-nano texture to the rotating frame, and perform a vacuum operation on the chamber. When the vacuum degree reaches 1.0 × 10 -5 After Torr, argon gas is introduced, the working pressure of the chamber is set to 2.5 mTorr, the rotation speed frequency of the rack is set to 120 Hz, the DC power supply is turned on to apply a 3A current to achieve sputtering of the graphite target, the deposition time is set to 160 min, no pulse negative bias is applied, and the thickness of the sensing film is about 1 μm. (4) Attach conductive copper foil to both ends of the sample obtained in the previous step as sensor electrodes.

[0060] Among them, the surface morphology and sensing performance of the sensor prepared under the 200-mesh mask are as follows: Figure 9 As shown, the deposited amorphous carbon film has a regular, complete, and ordered mesh structure. The sensor has a sensitivity of up to 11101.10 within a 50% strain range and a linear fit of up to 0.996.

[0061] Example 3 This embodiment provides a humidity-strain dual-response amorphous carbon-based flexible sensor, which consists of a PDMS substrate with micro-nano structure, an amorphous carbon film sensing layer, and a conductive copper foil sensing electrode.

[0062] The fabrication method of this humidity-strain dual-response amorphous carbon-based flexible sensor includes the following steps: (1) Place the PDMS substrate in the chamber. The substrate thickness is 200 μm, and the applicable temperature is -40℃ to 200℃. Place a 300-mesh stainless steel wire mesh on the substrate surface as a metal mask. Perform a vacuum operation on the chamber. When the vacuum degree reaches 3×10 -5 During Torr, oxygen is introduced at a flow rate of 100 sccm and the working pressure in the chamber is set to 20 mTorr. (2) The RF power supply parameters were set to -500V, 350kHz and 1.1μs to generate oxygen plasma for selective surface modification of the PDMS substrate for 10min. (3) Remove the metal mask, attach the PDMS substrate with micro-nano texture to the rotating frame, and perform a vacuum operation on the chamber. When the vacuum degree reaches 1.0×10-5Torr, argon gas is introduced. The working gas pressure of the chamber is set to 2.5mTorr, the rotation speed frequency of the frame is set to 120Hz, and the DC power supply is turned on to apply a 3A current to realize the sputtering of the graphite target. The deposition time is set to 160min, no pulse negative bias is applied, and the film thickness is about 1μm. (4) The conductive copper foil is bonded to both ends of the sample obtained in the previous step as sensor electrodes.

[0063] Among them, the surface morphology and sensing performance of the sensor prepared under the 300-mesh mask are as follows: Figure 10 As shown, the deposited amorphous carbon film has a regular, complete, and ordered mesh structure. The sensor has a sensitivity of up to 11101.10 within a 50% strain range and a linear fit of up to 0.996.

[0064] Comparative Example 1 In Comparative Example 1, the amorphous carbon-based flexible sensor consists of a PDMS substrate with micro-nano structure, an amorphous carbon film sensing layer, and a conductive copper foil sensing electrode.

[0065] The sensor fabrication method includes the following steps: (1) Place the PDMS substrate in the chamber. The substrate thickness is 200 μm, and the applicable temperature is -40℃ to 200℃. Perform a vacuuming operation on the chamber until the vacuum level reaches 3×10⁻⁶. -5 During Torr, oxygen is introduced at a flow rate of 100 sccm and the working pressure in the chamber is set to 20 mTorr. (2) The RF power supply parameters were set to -500V, 350kHz and 1.1μs to generate oxygen plasma for selective surface modification of the PDMS substrate for 10min. (3) Remove the metal mask, attach the modified PDMS substrate to the rotating frame, and perform a vacuum operation on the chamber. When the vacuum degree reaches 3.0 × 10⁻⁶, the vacuum level is 3.0 × 10⁻⁶. -5 After Torr, argon gas is introduced, the working pressure of the chamber is set to 2.5 mTorr, the rotation speed frequency of the rack is set to 120 Hz, the DC power supply is turned on to apply a 3A current to achieve sputtering of the graphite target, the deposition time is set to 160 min, no pulse negative bias is applied, and the film thickness is about 1 μm. (4) The conductive copper foil is bonded to both ends of the sample as sensor electrodes.

[0066] In Comparative Example 1, the prepared sensor performance is as follows: Figure 11 As shown, compared to other embodiments, the sensor prepared in Comparative Example 1 has lower sensitivity, with a maximum sensitivity of only 38 within a 50% strain range.

[0067] Comparative Example 2 The only difference between this comparative example and Comparative Example 2 is that the sensor's sensitive layer was prepared using plasma-enhanced chemical vapor deposition with acetylene as the precursor gas, and the chamber vacuum reached 3 × 10⁻⁶. -5 When the Torr is below 100 sccm, acetylene is introduced and a pulsed negative bias voltage of 450V is applied to deposit a 1μm thick amorphous carbon film.

[0068] In Comparative Example 2, it was found through testing that the amorphous carbon film prepared by plasma-enhanced chemical vapor deposition had excessive resistance, making it impossible to characterize the sensing performance of the device.

[0069] The humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method provided by the present invention have the following beneficial effects: (1) The ordered micro-nano structure control method of micro-nano flexible body is simple. By introducing ordered micro-nano structure, good sensing performance can be achieved, and it has the advantage of low cost and large-scale preparation. (2) It has ultra-high sensitivity and wide sensing range, and can realize dual-function response sensing for humidity and strain; (3) It has high temperature resistance, can be attached to the surface of various objects, has high stability and repeatability, and can be applied to fields such as human-computer interaction, electronic skin, smart wearables, health monitoring or flexible sensing; (4) Based on highly conductive amorphous carbon film sensitive material and unique micro-nano structured design, excellent strain sensing performance and humidity strain dual response function are realized.

[0070] The humidity-strain dual-response amorphous carbon-based flexible sensor and its fabrication method according to the present invention have been described above by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various modifications can be made to the fabrication method of the humidity-strain dual-response amorphous carbon-based flexible sensor proposed in the present invention without departing from the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the contents of the appended claims.

Claims

1. A humidity-strain dual responsive amorphous carbon based flexible sensor, characterized in that, The humidity and strain dual-response amorphous carbon-based flexible sensor comprises a flexible substrate, a sensing sensitive layer arranged on the flexible substrate, and a sensing electrode electrically connected with the sensing sensitive layer. The sensing sensitive layer is an amorphous carbon film, which is used for collecting external signals and transmitting the signals through the sensing electrode.

2. The humidity and strain dual-responsive amorphous carbon-based flexible sensor of claim 1, wherein, The strain sensing range is 80%<ε<210%, and the humidity sensing range is 35%-45%RH.

3. The humidity and strain dual-responsive amorphous carbon-based flexible sensor of claim 1, wherein, The thickness of the sensing sensitive layer ranges from 60nm to 1500nm.

4. The humidity and strain dual-responsive amorphous carbon-based flexible sensor of claim 1, wherein, The flexible substrate material comprises an elastomer and a polymer. The elastomer comprises at least one of butyl rubber, natural rubber and Ecoflex. The polymer comprises at least one of polydimethylsiloxane, polyimide, polyester and thermoplastic polyurethane.

5. A method for preparing a humidity and strain dual-responsive amorphous carbon-based flexible sensor, characterized in that, The method for preparing the humidity and strain dual-response amorphous carbon-based flexible sensor comprises the following steps: A flexible substrate is obtained, and the flexible substrate is pretreated by using a plasma modification technology to obtain a flexible substrate with a micro-nano structure without damage; A graphite target is sputtered by using a direct-current magnetron sputtering technology to deposit an amorphous carbon film on the surface of the flexible substrate with the micro-nano structure to form a sensing sensitive layer; Sensing electrodes are attached to both ends of the sensing sensitive layer to form the humidity and strain dual-response amorphous carbon-based flexible sensor.

6. The method of claim 5, wherein the humidity-strain dual responsive amorphous carbon-based flexible sensor is prepared by the steps of: The flexible substrate is placed in a chamber of a plasma treatment device, and a metal mask is bred on the surface of the flexible substrate to perform a vacuum operation; The flexible substrate is subjected to plasma modification based on the area selectivity of the metal mask to obtain the flexible substrate with the micro-nano structure. When the vacuum degree of the chamber of the plasma processing equipment reaches 1x10 -5 3x10 -5 Torr, the target gas is introduced, the gas is ionized by using the radio frequency power source, and thus the plasma is obtained.

7. The method for preparing the humidity and strain dual-response amorphous carbon-based flexible sensor according to claim 6, wherein The metal mask is made of at least one of iron, aluminum, copper and stainless steel. The metal mask has a planar structure, and is any one or a combination of a plurality of circular, rectangular, rhombic, elliptical, polygonal, strip-shaped, linear, silk-screen-shaped and array-shaped structures.

8. The method for preparing the humidity and strain dual-response amorphous carbon-based flexible sensor according to claim 6, wherein The target gas comprises argon, oxygen or nitrogen, and the flow rate of the target gas is 50-120sccm. The working gas pressure of the chamber of the plasma treatment device is 15-200mTorr, the working voltage is-500--250V, the radio frequency power supply frequency is 350kHz, the pulse width is 1.1μs, and the modification time is 30s-10min.

10. The method for preparing the humidity and strain dual-response amorphous carbon-based flexible sensor according to claim 9, wherein 9. The method for fabricating a humidity-strain dual-response amorphous carbon-based flexible sensor as described in claim 5, characterized in that, The flexible substrate with the micro-nano structure is placed on a rotating frame of the chamber of the magnetron sputtering device, and the rotation frequency of the rotating frame ranges from 100Hz to 120Hz. After the micro-nano structure flexible substrate is placed in the chamber of the magnetron sputtering device, vacuumizing is performed, argon is introduced when the vacuum degree reaches 8x10 -6 Torr, and current is applied to sputter a graphite target with a purity of 99.9% to deposit amorphous carbon film on the surface of the micro-nano structure flexible substrate. -5 Torr, and current is applied to sputter a graphite target with a purity of 99.9% to deposit amorphous carbon film on the surface of the micro-nano structure flexible substrate. ​ ​ The working pressure of the chamber of the magnetron sputtering device is 2.5-3.2 mTorr, the sputtering current is 2.5-3 A, the deposition temperature is 20-30 DEG C, and the sputtering time is 10-240 min, without applying a bias voltage.

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