A Flexible Ultra-thin Pressure And Strain Sensor Based On Silk Fibroin

With the explosive development of mobile terminals and the Internet of Things in recent years,wearable electronic devices have also shown an extremely broad prospect of commercial application,gradually penetrating into all aspects of people’s daily life,including portable household human health physiological signal monitoring,VR multi-mode human-computer interaction,robotic skin and exoskeleton,medical rehabilitation and other fields.It has brought great convenience and profound changes to the future social life.The global market has also put forward a higher demand for wearable devices,such as wearing comfort,non-invasive monitoring,zero-loss body perception function,and more functional integration of a single device.Flexible sensor components are the key breakthrough point of wearable technologies.Pressure and stretch,as important physiological signals of human activities,can reflect human health conditions to some extent,such as blood pressure,heartbeat,pulse,intraocular pressure,joint activity,etc.,and have important guiding significance for scar stress therapy.Therefore,the development of flexible ultra-thin non-invasive stress-strain intelligent wearable electronic devices that do not compromise the skin sensing function of the human body has an important strategic significance for promoting the implementation of personalized medical health monitoring system.This thesis is mainly divided into the following three aspects:Firstly,a flexible ultra-thin stress-strain sensor is proposed based on the non-invasive wearable electronics.Silk fibroin and hydrogel with good biocompatibility and mechanical stability is used as the substrate and functional layer,and the micro-structure is introduced through the gas-liquid interface self-assembly PS colloidal microspheres,so as to optimize the structure and improve the performance of the device.Moreover,the patterned Ag NWs flexible interdigitated electrode is prepared by mask spraying.The structure of interdigitated capacitor is fabricated and PU film with high transparency is used as encapsulation layer.Secondly,the measurement and characterization are completed,the overall thickness of the sensor is around～100μm,with good light transmittance（>80%）.Under the pressure mode,the maximum sensitivity can reach 0.87 k Pa^-1 and still have good durability and stability after working for more than 2000 times.As for the tensile strain mode strain mode,it can be stretched up to a maximum of 70%,with good resilience.At the same time,due to the property of sensing humidity of silk fibroin,it can also be used as humidity sensing function,with the maximum sensitivity up to 0.27%RH^-1,realizing the integration of a single device with three multi-sensing modes.Finally,the platform for facial expression,knuckle and elbow joint movement and upper respiratory physiological activity monitoring are established to verify the feasibility of its application in human health physiological signal monitoring.This thesis also demonstrates the grip and relaxation experiments of the intelligent manipulator,which provides the possibility for its application in the field of prosthetics.In order to expand its application scope,a data acquisition and display system based on LabVIEW is designed to realize a human-computer friendly display interface,including real-time waveform acquisition and pressure mapping of array devices,so as to build a distributed human health monitoring platform.