Study On The Construction And Performance Of PDMS-based Layered Flexible Strain-sensitive Conductive Polymer Composites

Flexible force-sensitive materials can withstand large strains and convert the strains into electrical signals that are easy to detect.They have important applications in wearable electronic devices,human sports health detection,and electronic skin.In view of the problems of high filler content,difficult compatibility of conductivity,stretchability,and sensitivity in polymer-based flexible force-sensitive conductive composite materials,this topic uses flexible polydimethylsiloxane(PDMS)as the matrix and adopts Strategies such as swelling penetration,natural settlement and magnetic field assist,adjust the distribution of fillers on the surface of the substrate,construct a layered highly flexible force-sensitive conductor with low filler content,and deeply explore the strain response mechanism and sensing performance of the material,and apply it to human motion Monitoring,as follows:(1)Firstly,using high elasticity polydimethylsiloxane(PDMS)as the flexible matrix and low-dimensional nano-CB(nCB)as the conductive filler were used,and a sandwich layered flexible force-sensitive material with gradient filler distribution was formed by swelling and percolation.nCB enters the surface and interior of PDMS swollen with hexane through diffusion.A few nCB diffuses into the inner area of PDMS,while most nCB remains in the surface layer,forming a gradient nCB distribution.The filler is enriched in the surface layer to ensure good conductivity,and the surface layer with high filler content is more sensitive to strain that is conducive to improving sensitivity.The filler content decreases with increasing depth,and the total filler content is low,which is beneficial to the stretchability of the composite material.PDMS/nCB flexible force-sensitive materials achieve an operating strain of 355%and a gauge factor(GF)of 343 at a content of only 6.2 wt%CB.Even at a high strain of 200%,the composite material also shows good cycling behavior.In addition,due to the rough surface,the surface of PDMS/nCB exhibits superhydrophobicity.(2)In order to improve the conductivity of flexible force-sensitive materials,nickel-coated graphite(NCG)with better conductivity has been introduced.The flexible force-sensitive material based on the layered structure PDMS was prepared by adopting a simple one-step sedimentation method of fillers.The high-density NCG settles and accumulates in low viscosity PDMS solution,and presents a two-dimensional conductive network at the bottom of the PDMS/NCG flexible force-sensitive material.Its percolation threshold(P_c)is only 2.52 vol%.When the NCG is 11.11 vol%,the conductivity of the flexible force-sensitive materials is up to 148 S/m.When stress is applied,the resistance of the composite material increases from 8~20Ωto 4×10~8Ω,and the GF is as high as 5.6×10~8.It exhibits excellent cycle performance in electromechanical cycling at 10%strain,and also shows excellent results in human application tests.(3)In order to further increase the operable strain of PDMS/NCG,a layered PDMS/NCG flexible force-sensitive material with oriented structure is induced by rubber magnetic paper.The rubber magnetic paper is composed of magnetic rubber strips with a width of about 2 mm and 1 mm of non-magnetic rubber alternately,where in the magnetic rubber strips sequentially show N、S、N、S、N、S···.Under the action of rubber magnetic paper,NCG exhibits two different structures.The NCG formed a horizontally oriented network overlap along the magnetic induction line above the magnetic stripe,and formed a vertically oriented discrete NCG island above the non-magnetic rubber.The high-quality NCG conductive network can significantly improve the working strain range of PDMS/NCG.When the NCG content is 0.04 g/cm~2,the conductivity is 23.10 S/m,the strain detection range is 196%,and the GF value is1.04×10~6,it is expected to be applied to flexible force-sensitive devices.