Preparation method of flexible sensor based on metal-doped vertical graphene

Abstract

The invention provides a preparation method of a flexible sensor based on metal-doped vertical graphene, the sensitivity of the sensor is improved by utilizing a graphene microstructure, meanwhile, a metal layer is introduced into a vertical graphene structure, preparation of a composite structure material is realized through the synergistic effect of EBEs / PECVD, and PDMS is adopted to assist in stripping VGNs, so that the flexibility of the flexible sensor is improved. The flexible pressure sensor with the metal particle doped graphene structure is constructed, the sensitivity of the VGNs flexible pressure sensor is improved to 40.15 kPa <-1 >, and the requirement for high sensitivity is met. And meanwhile, the flexible pressure sensor with the structure also has excellent cycle life and stability.

Description

Technical Field

[0001] This invention belongs to the field of wearable flexible sensor applications and relates to a method for fabricating a flexible sensor based on metal-doped vertical graphene. Background Technology

[0002] With the development of technology, many innovative technologies have emerged in fields such as intelligent robots, electronic skin, and human-computer interaction. Among them, flexible pressure sensors play an important role in the field of wearable electronics due to their efficient and rapid conversion between electrical and pressure signals. In the field of flexible pressure sensors, the most commonly used polymer composite materials include polydimethylsiloxane (PDMS) and polyimide (PI), while the most commonly used conductive nanomaterials are nanowires, carbon nanotubes, and graphene. For example, a flexible piezoelectric sensor based on a PbTiO3 nanowire / graphene heterostructure can achieve pressures as high as 9.4 × 10⁻³ kPa. -1 The sensitivity of the sensor for measuring static pressure was improved. Furthermore, researchers developed a flexible graphene / GaN / PDMS sensor based on the piezoelectric effect, which is extremely sensitive to compressive strain of 0.1% with a strain coefficient of 13.48. However, developing low-cost, simple-structured, tensile-resistant, and stable piezoresistive pressure sensors remains a significant challenge.

[0003] Sensitivity is one of the most important performance parameters in evaluating flexible pressure sensors. To improve this sensitivity, numerous researchers have proposed innovative ideas in materials and microstructure. Despite the significant efforts made by researchers to enhance sensor performance, fabricating low-cost, high-sensitivity flexible pressure sensors remains a challenge. Vapor nanosheets (VGNs) have been proven to possess excellent piezoresistive properties. Furthermore, due to their unique VGNs nanosheet structure, high conductivity, and stable chemical properties, VGNs are frequently used in various flexible sensors. However, reports on the application of VGNs in flexible pressure sensors are relatively limited. Therefore, studying the piezoresistive properties of VGNs is crucial for expanding their applications.

[0004] Metal-doped vertical graphene has significant application value in wearable flexible sensors. It is primarily fabricated using the PECVD method, typically at temperatures between 650-1050℃. In current reports, most flexible sensors based on metal-doped vertical graphene are first fabricated on a metal substrate, and then the metal-doped vertical graphene is transferred to a flexible polymer substrate using various methods. Therefore, the three-dimensional structure of the metal-doped vertical graphene prepared by this method is inevitably damaged during the transfer process, and metal residues are produced, thus affecting the sensor's performance. Furthermore, the reproducibility of flexible sensors based on metal-doped vertical graphene prepared by this method is low, and the etching solutions and other chemicals used in the transfer process can pollute the environment and harm human health. Summary of the Invention

[0005] This invention provides a method for fabricating a flexible sensor based on metal-doped vertical graphene. On a high-temperature resistant substrate, PDMS flexible material is bonded to metal-doped vertical graphene using inductively coupled plasma chemical vapor deposition (ICP-CVD). Subsequently, a flexible sensor based on metal-doped vertical graphene is fabricated by exfoliation.

[0006] The technical solution of this invention is as follows: a metal layer is introduced into a vertical graphene structure, and then the prepared metal substrate is placed in an inductively coupled plasma chemical vapor deposition (ICP-CVD) apparatus to deposit a 10 μm thick layer of vertical graphene. Through the synergistic effect of EBE / PECVD, a composite structural material is prepared, and PDMS-assisted exfoliation of VGNs is used to construct a flexible pressure sensor with a metal particle-doped graphene structure.

[0007] The beneficial effects of this invention are: it uses a high-temperature resistant flexible material as a substrate to fabricate flexible sensors by growing metal-doped vertical graphene without transfer. This avoids the damage to the metal-doped vertical graphene caused by the transfer process, as well as the environmental pollution and harm to human health caused by the etching solution used in the transfer process. Furthermore, by combining interdigital electrodes with metal-doped vertical graphene, it achieves the reproducible and large-scale fabrication of high-performance flexible sensors based on metal-doped vertical graphene, which can promote their commercial application. Attached Figure Description

[0008] Figure 1 Optical microscope image of the interface between the metal thin film and the vertical graphene on the substrate.

[0009] Figure 2 Transmission electron microscope image of metal-doped vertical graphene grown on a substrate.

[0010] Figure 3 Vertical graphene scanning electron microscope image.

[0011] Figure 4 A schematic diagram of a sensor packaged in PDMS.

[0012] Figure 5 Performance curves of vertical graphene pressure sensor. Detailed Implementation

[0013] The implementation steps of the present invention are further illustrated below through specific embodiments.

[0014] Step 1. Clean the substrate with SPM solution (hydrogen peroxide: concentrated sulfuric acid = 1: 4), acetone, isopropanol, and deionized water by ultrasonic cleaning to remove metal and organic matter from the substrate surface. Then, clean the substrate with nitrogen gas. Place the pre-cleaned stainless steel mask on the flexible substrate and put it into the magnetron sputtering instrument to sputter a metal layer with a thickness of 800nm.

[0015] Step 2. Place the grown metal substrate into a tube furnace at 500°C and atmospheric pressure, and introduce a 5% (by volume) H2 / Ar mixed gas for annealing for 1 hour to improve the adhesion of the electrode to the substrate.

[0016] Step 3. The substrate was then cleaned with acetone and isopropanol and purged with nitrogen. The substrate, with the electrode side facing up, was placed in a plasma chemical vapor deposition apparatus. A mixed gas of methane:hydrogen:argon = 2 sccm:40 sccm:50 sccm was introduced. The substrate was grown for 2 hours at a pressure of 20 Pa, an RF source power of 300 W, and a temperature of 700 °C to obtain metal-doped vertical graphene with a thickness of approximately 10 μm.

[0017] Step 4. A 200-300 nm metal layer is deposited on the surface of the graphene nanowall using techniques such as electron beam evaporation and magnetron sputtering. The substrate is then placed in a tube furnace, and an H2 / Ar mixed gas is introduced. The metal-grown sample is then annealed under normal pressure.

[0018] Step 5. Finally, encapsulate it with PDMS and peel the metal-doped graphene nanowalls encapsulated with PDMS off the substrate surface. Attach tin-plated copper wires to the electrode leads of the removed sample using conductive silver paste. Then, place the sample in a mold, uniformly drop-coat PDMS onto the device surface to completely encapsulate the device, and heat-cur the PDMS to complete the device encapsulation.

[0019] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for fabricating a flexible sensor based on metal-doped vertical graphene, characterized in that, Includes the following steps: (1) Place the substrate in a magnetron sputtering apparatus to grow a metal layer; (2) The substrate is placed in an inductively coupled plasma chemical vapor deposition device, and a CH4 / H2 / Ar mixed gas is introduced to grow metal-doped vertical graphene. (3) A metal layer is deposited on the surface of the graphene nanowall using techniques such as electron beam evaporation and magnetron sputtering; (4) Place the substrate in a tube furnace, introduce H2 / Ar mixed gas, and anneal the grown metal sample under normal pressure; (5) Finally, it is encapsulated with PDMS and the PDMS-encapsulated metal-doped graphene nanowalls are peeled off the substrate surface.

2. The method for fabricating a flexible sensor based on metal-doped vertical graphene according to claim 1, characterized in that, In step (1), the metal layer can be a conductive metal such as Cu, Ni, or Co.

3. The method for fabricating a flexible sensor based on metal-doped vertical graphene according to claim 1, characterized in that, In step (2), the annealing conditions are: H2:Ar flow ratio of 25 sccm: 500 sccm, atmospheric pressure, temperature of 500℃, and time of 1h.

4. The method for fabricating a flexible sensor based on metal-doped vertical graphene according to claim 1, characterized in that, In step (3), the growth conditions for metal-doped vertical graphene are: the flow ratio of H2:Ar is 4 sccm:5 sccm, the pressure is 20 Pa, the temperature is 300 ℃, and the metal layer can be conductive metals such as Cu, Ni, and Co.

5. The method for fabricating a flexible sensor based on metal-doped vertical graphene according to claim 1, characterized in that, In step (4), the specific encapsulation content is as follows: a PDMS encapsulation with a basic component to curing agent ratio of 19:1 is used, and the thickness of the encapsulated device is 2mm.

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