Wavy Graphene-based Materials For Pressure Sensors And Moisture Actuators

Wavy graphene film with periodic structure is a stretchable material that transforms from 2D structures to 3D structures.In this paper,we explored and optimized the fabrication process of wavy graphene films on the basis of the wavy structural features.As the gradient structure was introduced into wavy graphene films,we studied the properties of these wavy graphene films with gradient nature for pressure sensors.And we also designed an asymmetric graphene oxide(AGO)film for moisture actuator.Specific work was carried out by the following parts.1.Based on the pre-strain method,we explored and optimized the fabrication process of wavy graphene films.In addition,several factors with the effects on the morphology of wavy graphene films were discussed.2.We for the first time fabricated a wavelength-gradient graphene oxide(WGGO)film and its reduced product,wavelength-gradient reduced graphene oxide(WGrGO)film.Then the WGrGO films were used for pressure sensors which exhibited different pressure-sensitive performances in the different areas.Furthermore,this novel type of pressure sensor exhibited a three-segment pressure response curve:a sensitivity of 46.2 kPa-1 below 400 Pa,a sensitivity of 69.6 kPa'1 at 400-1500 Pa,and a sensitivity of 60.6 kPa-1 at 1500-5000 Pa.Besides,a series of pressure-sensitive properties were also characterized,including I-V curves,minimum test pressure and its response time,reliability and repeatability.3.We simply used GO to fabricate a sole GO film with an asymmetric structure which consisted of a wavy layer and a smooth layer.Due to the asymmetric structure and excellent hygroscopicity of GO material,the asymmetric graphene oxide(AGO)film(2.5×0.5 cm2)was responsive to moisture that has a maximum bending angle change of?=1800°as the relative humidity(RH)changed from 35%to 85%.Compared with other reports about moisture actuators,the AGO film exhibited a superior bending capability.Furthermore,we propose a novel mechanism for moisture actuation of the AGO film based on our detailed observations,and a wavy structure has been introduced for a great potential in bending deformation.