Research Of Preparation And Response Optimization Of Flexible Pressure Sensor Based On AgNWs

Recently, flexible and stretchable artificial electronic sensors have increasingly drawn much attention. Flexible pressure sensor with good flexibility, not only can be attached on the complex surface of object, but also can be attached to the body. Because of the strechability of the flexible sensor, the sensor has potential applications in robot,consumer electronics, wearable health care systems, human-machine interfacing devices,and artificial intelligence, display device, aerospace nondestructive testing. New-type flexible pressure sensor is similar to human skin which can be stretched and feel the awareness of the external force, can be used for bionic electronic skin and kinds of wearable electronic devices, which has caused wide attention of academia and industry in recent years.The results show that the design of flexible stress sensor is based on high molecular polymer materials such as polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), polyimide (PI), polyethylene terephthalate Glycol (PET) and conductive rubber. The carbon nanotubes (CNT), silver nanowires (AgNWs) and other materials are used as flexible electrode. High sensitivity, large area, flexibility, high elasticity, high spatial resolution and other performance indicators are the key characteristics of flexible pressure sensor application. Focusing on practical application prospects, the pressure sensor based on the development of excellent features, high sensitivity and simple production process, low cost of flexible materials, has important scientific and practical significance.According to the principle of operation, flexible pressure sensors are mainly divided into piezoresistive, capacitive and piezoelectric sensors. The flexible capacitive pressure sensor based on silver nanowires is mainly to improve the performance of the sensor by the optimization of sensitive materials and the structure of flexible substrate.In this thesis, we used polydimethylsiloxane (PDMS) as the flexible substrate, silver nanowires (AgNWs) as the sensitive material, polydimethylsiloxane (PDMS) as the dielectric layer, and using simple, low cost method to prepare a capacitive pressure sensor, and improved the performance of the sensor with optimize the structure of the device. Mainly research are as the following aspects:In this thesis, we improved the preparation method of silver nanowires, and studied the influence factors of silver nanowires. The factors affecting the growth of silver nanowires were studied from the aspects of relative molecular mass, molar ratio of AgNO3 and PVP, metal salt concentration and reaction temperature. And then the reaction conditions were optimumed to prepare pure, high aspect ratio silver nanowires.A thin film of silver nanowire electrode was fabricated by spray coating, dropping and spin coating method, respectively. We reported a simple and low-cost method to fabricate large-area PDMS conducting thin films with microstructures. The flexible substrate film with different structure was prepared by using micro-structured glass template and plane glass template. The electrode film and flexible substrate film were encapsulated into the capacitive pressure sensor with "Sandwich structure". The reported sensors with micro-structured electrodes demonstrate better performance with higher sensitivity (1.1 kPa-1), lower detection (IPa), a faster response time (<1s) and better stability than that of the sensors without microstructures.In our work, we combined the pressure device, device structure, signal acquisition device and oscillation circuit to build a flexible pressure sensor on-line detection system.The system effectively combined the sensor with the oscillation circuit, and can convert the capacitance value of the capacitive sensor to the opposite voltage and frequency signal, which can be directly collected by the computer and make the capacitive sensor test equipment simple. The measurement method has the advantages of low cost, high measurement precision, fast response time, stable operation and strong anti-interference ability.