| In recent years,with the booming development of flexible electronic technology,flexible wearable strain sensors have shown great promise in various fields such as medical,environmental protection,smart home and robotics.However,it is still challenging to fabricate flexible sensors with high sensitivity,wide operating range,excellent durability and antibacterial properties.In this study,with the aim of improving the sensitivity,sensing range and durability of flexible strain sensors,two types of flexible strain sensors for different strain directions were prepared using thermoplastic polyurethane(TPU)polymer elastomer with excellent elasticity and wear resistance as the substrate material,combined with the synergy of multiple conductive networks between carbon nanotubes(CNTs)and silver nanoparticles(Ag NPs).The two strain sensors were tested for their mechanical,electrical and sensing properties.The details of the study are as follows:(1)TPU nanofibre films with uniform fibre diameter were prepared using an electrostatic spinning process.Subsequently,the TPU membranes were immersed in different concentrations of carbon nanotube aqueous dispersion(CNAD)by adsorbing CNT on the fibre surface in order to form conductive pathways.The TPU/3CNT stretching type flexible strain sensor was prepared by characterising by scanning electron microscopy that the fibrous membrane was best immersed in 3 wt.%concentration of CNAD.The strain sensor was then tested for sensitivity and cyclic loading.The results showed that the strain sensor was sensitive up to 134 and had a wide operating range(10%-500%),was stable under repeated cyclic loading(1000cycles of cyclic stretching at 200%strain)and was able to differentiate between different levels of strain.(2)A TPU/3CNT@Ag NPs tensile flexible strain sensor with a dual conductive network was prepared by in situ growth of Ag NPs on the surface of TPU/3CNT fibres by a simple reduction process after immersion in silver nitrate solution(SNS).The experimental results show that the prepared strain sensor has excellent stability and durability(1400 cycles at 200%strain),while the dual-conducting network structure significantly improves the sensitivity of the sensor(GF=930)and broadens the sensing range(0.1%-500%).In addition,the sensor has a fast response(100 ms at 1%strain)and a very high dynamic monitoring rate(2400 mm/min),can be used in acidic and alkaline environments,is bacteriostatic against common strains of bacteria(Staphylococcus aureus and E.coli)and has potential for use in health monitoring and voice recognition devices.(3)Vc-TPU foam with a three-dimensional through-hole structure was prepared using a salt template vacuum casting process,and Vc-TPU/0.1CNT@Ag NPs compressive strain sensors were successfully prepared by a simple soak-adsorption and reduction process.The sensor sensitivity curve has excellent linearity(0-70%strain,R~2=0.99875),ultra-fast response and recovery times(both 20 ms),excellent rebound range(70%),good stability and durability(500 cycles at 50%strain),wide sensing range(5%-70%)and detection of microstrain(tendon,blow)and large strain The ability to detect micro-strains(tendon,blow)and large strains(foot pedal)has shown promise in areas such as human movement monitoring. |
