Interface Structure Design And Sensing Mechanism Of Polyvinyl Alcohol-based Multifunctional Flexible Sensing Materials

With the rapid development of intelligent electronic devices,the research work on flexible sensors has gained extensive attention.In general,conductivity and sensing signal stability,critical factors in sensing performance and signal capture applications,must be considered when developing flexible sensors.Constructing a conductive network by introducing conductive nanoparticles into polymer elastomers is one of the general strategies for preparing flexible sensors.Since the conductive particles are embedded in the flexible polymer matrix,firstly,the matrix material will block the conductive particles inside the polymer.Openly,the conductive network structure constructed will have certain defects.Secondly,the conductive particles are easy to agglomerate in the flexible polymer matrix,resulting in the uneven distribution of the conductive network and the lack of interaction between adjacent conductive particles.When the strain/release stimulus is applied,the agglomeration causes the relative position of the nanoparticles to change.As a result,the resistance of the conductive network changes irreversibly,resulting in poor stability of the sensing signal.Due to its limited structural design,the traditional flexible sensor restricts the improvement of the conductivity of the sensing material and the sensing stability.Moreover,it primarily uses a single-point monitoring sensor design.This significantly limits its application as a flexible sensor in human health monitoring and electronic skin.Therefore,the integrated innovative interface structure design and integrated multi-point sensing system meet the requirements of flexible sensors for high conductivity,high sensitivity,and multi-level monitoring.（Ⅰ）Highly sensitive flexible sensing material with microcrack structure and multiple signal capture:Using polyvinyl alcohol（PVA）as the matrix material,cellulose nanocrystalline-polyaniline hybrid material（CNC-PANI）was loaded on the surface by coating technology,Nafion was used as the binder to prepare a highly conductive and highly sensitive flexible sensing material with a micro-crack structure.The signal responses to external stimuli such as strain,temperature,and humidity were explored in detail.Thanks to the introduction of the adhesive Nafion for the first time,strong interfacial interaction and a complete conductive network structure are formed between the conductive unit and the flexible PVA substrate material,which endows the flexible sensing material with excellent electrical conductivity,sensing stability,Mechanical properties and solve the problems of friction resistance and durability that have always existed in sensing materials.As a multi-functional sensor,the composite film can monitor signal changes such as stretching,temperature,and humidity in real-time and provides a basis for developing flexible sensing materials with multiple signal responsiveness,excellent sensing stability,and super wear resistance.（Ⅱ）Exploration on construction of flexible sensing materials and multi-point sensing system based on interfacial self-assembly of Marangoni effect:Based on alternate spraying technology,a flexible and high-strength PVA/CP₄₀ sensing material with multiple conductive networks was constructed by using CNC-reinforced PVA composite film as the matrix material and self-assembly using the Marangoni effect.The real-time monitoring and self-healing properties of flexible sensing materials in human physiological signals are deeply explored.An integrated multi-point sensing system has been developed to monitor in real-time whether strength training actions comply with safety regulations,and an innovative non-overlapping Morse code system for sensors has been defined to achieve effective Morse code communication for groups of people.Due to its super mechanical properties,excellent sensing stability,and fast response,this flexible sensing material has broad applications in emerging flexible electronics and various intelligent applications such as human health monitoring.