Superhydrophobic Strain Sensor Based On Rubber Matrix/silver Conductive Coating

With the advent of the era of intelligence,the demand for flexible wearable electronic devices continues to grow.As a part of wearable electronic devices,strain sensors are widely used in the fields of human health monitoring,electronic skin,human-machine interface,etc.Conductive polymer composite(CPC)has become an ideal material for strain sensor due to its excellent merits of light weight,easy processing,adjustable conductive network structure.In recent years,various CPC strain sensors have developed rapidly.However,it is still a challenge to develop multifunctional strain sensors with high conductivity,excellent sensing performance and durability,and strong environmental applicability.In this paper,the interaction between silver precursor and double bond and aromatic ring in rubber is used to construct silver conductive network.A series of conductive rubber composites with strong interfacial interactions are prepared by interface design and regulation(including bonding of silver nanoparticles to small molecules with low surface energy,introducing silicon rubber molecules with crosslinking network structure or swelling and phase separation of matrix molecules).The high electrical conductivity and superhydrophobic(oleophobic)properties of the material can be achieved simultaneously without sacrificing its flexibility.When used as a strain sensor,its special conductive network gives the material high sensitivity.Superhydrophobic properties broaden the application range of the sensor,allowing the sensor to work in high humidity,corrosion and cold environment.In addition,the sensing mechanism is clarified based on the evolution of conductive network during stretching-releasing process.This paper provides a new idea for developing high-performance and functional flexible strain sensing materials.The research content of this paper mainly includes the following five parts:1.Preparation and sensing performance of superhydrophobic RB/AgNPs/OCA composite.In this chapter,a fluorine-free superhydrophobic rubber/silver nanoparticles/stearic acid(RB/AgNPs/OCA)composite is prepared by one-step impregnation method.The interaction between conductive particles and low surface energy materials is analyzed.The sensing performance of the composite strain sensor is tested and it can be used for human motion monitoring.The sensing mechanism of the composite is revealed by data fitting and observation of the microstructure evolution of the composite under different strains.2.Preparation and sensing performance of superhydrophobic RB/PDA/AgNPs/PFDT composites.Rubber/polydopamine/silver nanoparticles/1H,1H,2H,2H-perfluoro-decyl mercaptan(RB/PDA/AgNPs/PFDT)composites are prepared by multi-step impregnation method.In order to improve the interfacial interaction between AgNPs and RB,a "universal adhesive"PDA is introduced on the RB surface,and the PDA layer provides a fixed site to anchor AgNPs on the matrix surface.At the same time,in order to further improve the superhydrophobic properties of the composite,a fluorinated long-chain molecule(PFDT)with lower surface energy is selected to modify the surface of silver nanoparticles.The influence of PFDT on the hydrophobicity of the material surface is studied.The strain sensing performance of the sensor is tested.The sensing mechanism is investigated by data fitting and observation of the microstructure of the composite under different strains.3.Preparation and sensing performance of superhydrophobic RB/AgNPs/PDMS composites.In order to further enhance the interfacial interaction between conductive particles and RB,silicone rubber molecules with crosslinking network structure are introduced between Ag nanoparticles.The cured silicone rubber coating not only greatly improves the interfacial interaction,but also acts as a low surface energy material to give the composite superhydrophobic properties.Finally,a conductive superhydrophobic RB/AgNPs/PDMS composite with multiple core-shell structure is prepared.The interfacial stability of composites is studied.The strain sensing behavior of the sensor under different strains is tested.The feasibility of applying the sensor to human body movement monitoring is explored,and the sensing mechanism of the sensor is analyzed.4.Preparation and sensing performance of superhydrophobic RF/AgNPs composites.On the basis of the research contents of the first three parts,in order to simplify the material preparation proces,the self-derived superhydrophobic conductive rubber sponge(RF)/AgNPs composite is prepared by the method of "metal ion reduction and synchronous polymer phase separation".The mechanism of self-derived superhydrophobicity and interface enhancement is analyzed.The response behavior and durability of the sensor under different tensile and compression strains are tested.The feasibility of sensors as wearable devices to monitor human movement in different forms(tensile and compressive deformation)is explored.The sensor behavior in different stages is analyzed.5.Preparation and sensing performance of superamphiphobic RF/F-AgNPs composites.On the basis of the research content in the fourth part,in order to further broaden the application scope of the material,the surface of the RF/AgNPs composites is modified with long-chain molecules with low surface energy:triethoxy-1H,1H,2H,2H-tridecafluoro-Noctylsilane.The silanoxy functional groups in the molecular chain can release low molecular alcohols after hydrolysis,and the resulting active silanol can chemically bond with silver nanoparticles and oxygen-containing groups in the matrix,so as to obtain superamphiphobic RF/F-AgNPs composites.The microstructure and chemical composition of the composites are observed.The stability of superamphiphobicity and conductive properties of the composite is tested.The sensing behavior and durability of the sensor under tensile or compressive strain are tested.The sensor is applied to human body motion detection to monitor different forms of human body motion,and the influence of material microstructure on sensing behavior is analyzed.