Study Of Flexible Mechanical Sensors Based On Carbon Nanomaterials

E-skin is an electronic device that simulates human skin to perceive subtle external stimulus signals.It is formed by integrating various high-performance functional sensors on a flexible substrate,and has important applications in artificial intelligence and artificial interactive health monitoring and motion detection.Flexible strain sensor play an important component of electronic skin,which can detect complex deformation caused by different parts of the body.The electrode system also is a factor determining the stability of the strain sensor.In recent years,with the development of flexible wearable electronic devices,the electrode system that is highly compatible with the main device has been put forward higher and higher requirements.It is required that the electrode can adapt to complex deformation conditions and maintain its stable performance to design an electrode system that is highly compatible with the main device has gradually become a focus of people’s attention.Here,we present a carbon nanotube integrated electrode(CNTIE)by wet-pulling the ends of a CNT film to form condensed thin fibers that resemble conventional conducting wire electrodes.A flexible strain sensor was constructed consisting of the middle CNT film as main functional part and the CNTIE as self-derived electrodes,with inherent CNT connection between the two parts.The sensor can be transferred to versatile substrates(e.g.balloon surface)or encapsulated in thermoplastic polymers(TPU),exhibiting a large linear response range(up to 1000% in tensile strain),excellent durability and repeatability over 5000 cycles,as well as the ability to detect small to large-degree human body motions.In addition,we simulated different application environments of flexible wearable devices in real life.CNTIE/TPU strain sensor not only maintained stable resistance changes in sweat environment,but also maintained stable operation under water and high temperature.In order to improve the sensitivity of CNT strain sensor,we prepared hybrid films(MXene/CNTIE and graphene /CNTIE composite films)based on CNTIE.The strain sensor was prepared by using CNTIE composite film encapsulated by TPU.The MXene/CNTIE/TPU strain sensor and the graphene /CNTIE/TPU strain sensor also shows superior linearity and stability at strain range of 0%-800%.As a result,the gauge factor of the strain sensos with graphene/CNTIE and MXene/CNTIE hybrid films are 0.527,and 1.43,respectively,which are 1.46 and 3.97 times of the CNTIE strain sensor.Based on the above results,compared with the sensors using traditional silver wire electrodes and separately fabricated CNT fiber electrodes,our CNTIE play an important role in achieving highly stable performance in the strain cycles.Our self-derived integrated electrodes provide a potential route to solve the in-compa tibility issues of conventional electrodes,and to develop high performance flexible and wearable systems based on carbon nanotubes and other nanomaterials.