| With the rapid development of electronic information technology,flexible electronic device has attracted widely attention for its flexibility and portability.Conductive silicon rubber(CSR)is a unique flexible conductive composite with unique electrical conductivity and biocompatibility and has been widely used in electromagnetic shielding,sensing and flexible device.The rapid development of production and analysis technology provides new opportunities to CSR.This paper focuses on the formulation of CSR to be 3D-printed(3DP)and fabrication of flexible sensor based upon it.Dispersion coefficient has been established to character the dispersion degree of fillers in the CSR.Formulation of CSR and parameters of 3DP process has been determined.Key property of flexible array capacitive sensor(FACS)and flexible screw resistance sensor(FSRS)based on 3DP process are further studied.The FSRS with excellent stable resistance response has been eventually applied to identify a superimposed load and detect joint motion.Dispersion coefficient based on gray extraction of microscopic picture was effectively to character the dispersion degree of fillers in CSR.The projection of the filler at some spacial depth could be obtained by the extraction of the gray value of its two-dimensional microscopic picture.Larger filling amount of filler in CSR resulted in better dispersion condition.Dispersion coefficients of three samples in uniform,uneven and extremely uneven dispersion states were 76.65%,50.28% and 8.09% respectively,which verified the Characterization significance of the dispersion coefficient.Formulation of CSR based on silver-coated glass fiber(AGF)and carbon fiber(CF)exhibited excellent electrical property.Synergistic effect of CF and 1,2 propanediol,matching with printing parameters improved the shape retention and the corresponding accuracy of 3DPed CSR.An introduced embedded 3DP(e-3DP)process provided an integrated forming way with high production efficiency comparing to traditional layer-by-layer(ll-)3DP process.FACS and FSRS were fabricated with ll-and e-3DP processes,respectively.The FACS was featured with five-layer structure with layers of encapsulative,top electrode(e-),middle dielectric(d-),bottom electrode,and bottom support in turn.Capacitance change of sensing unit in FACS array was about 10% to compressive load of 10 N,while about half interference response occurred in the adjacent units,which could cut half more by reducing the width of the electrode connecting wire from 8 cm to 1 cm.The FSRS was composed of an internal screw CSR wire and external PDMS encapsule.It was sensitive to tensile strain load at different loading rate with a stable sensitivity of 8-12.The FSRS recoveried its resistance exponentially as the load released.FSRS showed stable resistance response to load in 600 cycles.With aids of fast fourie transition analysis,the FSRS was capable to distighish the frequency and intensity of a superimposed load with frequencies of 1/12 Hz and 1/36 Hz.In addition,the sensor was sensitive enough to response to human motions including wrist bending with angles of 15 °,30 ° and 60 °,stepping at frequency of 1Hz and two-finger bending at frequency of 0.4Hz and 1.2Hz,simultaneously. |
