Preparation Of Graphene-based Strain Sensors And Their Applications

Wearable flexible strain sensors have recently attracted extensive attention because of their conformal attachment on the human body and long-term monitoring capabilities.They can be used in a variety of fields including heath-monitoring,electronic skin,human motion detection,and human-machine interfaces.However,the development of strain sensors with wide sensing ranges and high sensitivity is still a big challenge.Although much effort has devoted to improving their sensing performance,strain sensors capable of measuring multiple deformations for full-range detection of human motions have not yet been reported.Graphene has excellent mechanical,electrical,and optical properties;this it has been explored as sensing layers of strain sensors.In this thesis,the preparation and application of graphene-based strain sensor with large stretchability,high sensitivity and wide sensing range are investigated.Hydrazine hydrate reduced graphene oxide was used as the conductive sensing layer and the elastic tape as the stretchable substrate.This strain sensor with a fish scale-like graphene sensing layer can be fabricated via a simple pre-stretching/releasing the composite films of rGO and elastic tape.This preparation method does not require expensive manufacturing equipment,complicated chemical vapor deposition of graphene and toxic organic solvents,making the process to be simple,cheap,energy-saving,and scalable.The strain sensor has excellent overall performance;it can be used to detect stretching and bending deformation with a wide sensing range(> 82% strain),high sensitivity(gauge factor of 16.2 to 150),ultra-low detection limit(< 0.1% strain),excellent reliability and stability(> 5000 cycles).More importantly,this strain sensor can commendably monitor the fullrange human motions,from pulse and phonation of slight deformation to the joint bending of substantial movement.This is the first strain sensor based on the fish scale-like graphene sensing layer.Its unique microstructure allows the adjacent overlapped graphene sheets to be easily changed via reversible slippage,thereby changing their contact resistance.