Preparation And Properties Of Graphene-based Flexible Sensing Materials

As the basis of flexible electronic devices,flexible sensing materials have been paid increasingly attention with the rise of artificial intelligence and Internet of Things in recent years,which has triggered a research boom.Two-dimensional materials represented by graphene have become the preferred raw materials due to their ultra-thin thickness of single atomic layer and unique electrical properties.Flexible sensing materials and devices can be constructed by composite with flexible matrix.To accurately construct the microstructure of complex and to achieve high sensitivity,stable and repeatable response are still the focus and difficulties of the current research on graphene-based flexible sensing materials.In this paper,GO solution prepared by modified Hummers’method was combined with methylcellulose and natural rubber respectively to prepare graphene-based aerogels and graphene films.By controlling the conditions,the microstructure of wrinkles and orientation was introduced into the graphene-based complex,and the flexible graphene-based sensing material with high sensitivity and extremely stable performance was obtained.This paper describes the response properties of various flexible sensing materials and explores their applications in piezoresistive sensors,strain sensors and stretchable batteries.The specific works are as follows:（1）Methylcellulose reinforced graphene-based aerogel（MC/GA）was designed and constructed,and its piezoresistive sensing performance was studied.MC and GO composite aerogel prepared by directional-freezing and frozen-drying has excellent orientation structure.To maintain the flexibility and structural integrity of the aerogel,GO was gently reduced by water vapor at 120 ^oC,while holes and wrinkles were introduced.The finite element analysis shows that the porous wrinkled lamellar structure is beneficial to stress dispersion.The piezoresistance sensor based on MC/GA has high sensitivity(9.38 k Pa^-1),low detection limit（4.4 Pa）,good linearity and wide linear range（0-17 k Pa,R²>0.997）,short response and recovery time（<40 ms）,and good cycle stability（more than 20,000 times）.It overcomes the limitations of low linearity and instability of traditional GA-based sensors.（2）Grade-orienting wrinkled graphene films（WG@R）were prepared using rubber as substrate by step shrinkage method,and their strain sensing properties were studied.GO is sprayed onto a pre-stretched rubber substrate and progressively contracted to form pleats with graded orientation.After hydrazine vapor reduction,the wrinkled r GO films obtained are anisotropic.The gauge factor（GF）of WG@R-5-60 along the direction of primary wrinkles and secondary wrinkles are 0.15 and 28.3,respectively.Further application of patterning on the basis of hierarchical wrinkles shows that the design of fringe lines can significantly increase the strain sensing performance.After patterning,the GF of PWG@R-5-60 further increases to 49.5.The strain sensor based on PWG@R can monitor vital signs of throat and wrist and sense big movements of fingers,which has great application potential in the field of health and movement monitoring.（3）The structure of GO-CNT-GO-based sandwich wrinkles（GCG@R）and its flexible electrode properties were explored.Using carbon nanotubes as the main conductor and GO as adhesive and protect layer,a stretchable wrinkled sandwich structure electrode material was constructed and assembled into zinc-ion battery,which has stable voltage and power output under tensile state.It can provide stable voltage output for wearable integrated motion detection equipment.