Study On The Flexible Capacitive Strain Sensor And Its Effect Factors On Sensitiyity

Flexible strain sensor are emerging as important applications for futuresoft robotics, portable consumer electronics, touch-on flexible display andhealth diagnosis because their excellent flexibility allows them working withirregular or rigid objects. The sensitivity of sensor have received growingattentions, however, it is still quite challenging to achieve high sensitive andlarge area sensor with simple, low cost and low energy processes. In this work,the large area stretchable conductors were made by embedding retiform silvernanowires(AgNWs) films in poly(dimethylsiloxane)(PDMS) with low cost andlow energy processes. Besides, flexible capacitive pressure sensors andstretchable tension sensors based on flexible conductor were made. In orderto improve the sensitivity of flexible force sensor, the optimizing metheodsbased on materials and structure were proposed and studied. Spcific researchcontents and innovations are as follws:Pure and high draw ratio silver nanowires were successfully synthesizedby optimizing polyol process. The AgNWs were about80nm in diameter and20μm in length respectively.A novel, efficient, low-cost strategy was presented to fabricate large-areaelastic electrode. Different micro-structured electrode molded by micro-porousphoto paper. Besides, highly sensitive, flexible-elastic pressure sensors weredeveloped by optimizing package, micro-structure of electrode, conductivematerials, dielectric layer and substrate layer. The optimizing pressure sensordemonstrates a high sensitivity of1.15kPa-1and can detect tiny pressure aslow as20mg.The strechable conductor based on AgNWs percolation network wasachieved. The stretchable conductor kept relatively stable resistance afer50cycles of stretching/releasing in50%tensile strain. The capacitive tensionsensors was fabricated with two stretchable electrodes, which showedexcellent linearity under a very large strain range and the minimum detectable strain is0.89%.The flexible strain sensors with simple, low cost and low energy processespresented in the work can detect tiny pressure, it can be used in monitorsignals ranging from human heartbeats to vocal vibrations of throat in thefuture.