Development Of Flexible Strain Sensor And Its System Based On Electrical-Double Layer Effect

Somatosensory human-computer interaction,as a new type of human-computer interaction technologies,has broad applications in fields of medical health,cultural entertainment,and industrial control.The core components of a somatosensory human-computer interaction system are various functional sensors,of which strain sensors that can detect strains caused by human behavior are particularly critical.However,a majority of traditional strain sensors have some disadvantages such as hard structure,small strain detection range and low sensitivity.In this work,we utilized synthesized flexible and highly stretchable hydrogel as the substrate of the strain sensor and proposed to incorporate high-conductivity silver nanowires into the hydrogel.Hence,we successfully developed a flexible,wearable and high-performance capacitive-type strain sensor,which was based on the electrical-double layer large-capacitance effect formed at the hydrogel/metal interface.The device presents a wide strain detection range,high sensitivity and good biocompatibility.The main contents of this work are involved of the following three parts:1.We proposed the use of biocompatible hydrogel as the elastic material of the flexible and wearable strain sensor.The hydrogel material was synthesized by blending sodium alginate electrolyte and acrylamide polymer to form a crosslink network.It exhibits ultra-high stretchability and large stretching range up to 1000%.2.We successfully developed a flexible and wearable capacitive-type strain sensor based on biocompatible hydrogel materials.According to the electrical-double layer effect at the electrolyte/metal interface,we established an equivalent circuit model at the hydrogel/metal interface,and deeply investigated the electrical-double layer effect at the interface.Based on theoretical studies,we proposed to incorporate highly conductive silver nanowire networks into the hydrogel to construct a hydrogel/silver nanowire nanocomposite structure.The experimental results show that the device with silver nanowires has much better performance than that without silver nanowires;also,the electrical-double layer capacitance and the strain sensitivity are enhanced by 200 times and 1000 times,respectively.3.We constructed a somatosensory human-computer interaction system based on flexible and wearable capacitive-type strain sensor,and we successfully used it to realize dynamic and real-time monitoring on physiological signals of human body such as pulse,ECG,limb movement,speech and blinking.Finally,we used time-to-digital conversion technology to design and develop an capacitive-type signal acquisition system based on PS021 integrated chip,providing foundations for realizing practical somatosensory interactive systems that contain flexible and wearable capacitive-type strain sensors in the future.