Research on the preparation and performance of fabric-based ionic skin for human-machine interaction
As interest in human-machine interaction and health monitoring continues to rise,the field of flexible electronics has accelerated its development,with flexible electronic skin becoming a focal point of research.Traditional rigid conductive materials used to construct electronic skin often fail to provide stable sensing under high deformation,presenting issues such as low biocompatibility and opacity.These limitations necessitate the urgent development of wearable flexible electronic skin that can meet user needs effectively.This study aims to address the problem of limited application scenarios for ionogel-based ionic skin by proposing a research strategy centered on the use of a soft and comfortable textile structure as the substrate for the ionogel.Inspired by the ion conduction function of human skin,we explored the potential of stretchable ionic conductors,which transmit electrical signals similarly to human skin.Recent years have witnessed the widespread application of ionic skin in flexible wearable technology,including robotics,medical monitoring,and human-machine interaction.The ionic skin can be categorized into several types,including organic gels,conductive hydrogels,and ionogels.However,organic gels often exhibit low conductivity and poor biocompatibility,making them unsuitable for wearable applications related to human interaction.Conductive hydrogels,on the other hand,are susceptible to environmental humidity and temperature changes,which adversely affect their mechanical properties and electrical signal stability.This variability severely impacts sensing performance and restricts the application of sensors in practical scenarios.In this context,ionic liquids represent a green electrolyte with outstanding thermal stability,chemical stability,ionic stability,conductivity,and interfacial capacitance.Ionogels composed of ionic liquids and polymers have been developed to overcome the water loss problem associated with ionic hydrogels.These gels serve as effective materials for capacitive pressure sensing,exhibiting high sensitivity and durability,along with excellent environmental stability.Despite these advantages,many polymers used to prepare ionic gels involve organic solvents,which conflict with sustainable development goals.To overcome this challenge,we selected waterborne polyurethane as an eco-friendly polymer matrix,utilizing water as the solvent to avoid the use of harmful organic solvents.This selection not only aligns with green chemistry principles but also enables structural design through the integration of ionic liquids,allowing us to modulate mechanical properties and elasticity to meet diverse application needs.An effective strategy to enhance the sensing performance of ionogels involves constructing microstructures on their surfaces,which can take various microstructures such as micro-pyramid arrays,wrinkles,and micro-column arrays.However,these microstructures typically respond only under low pressure,significantly limiting their potential applications.Therefore,the development of ionogel-based electronic skin suitable for multiple scenarios has become a crucial research direction.In this study,we synthesized waterborne polyurethane with excellent biocompatibility as an elastomer and selected ionic liquids as conductive materials.Using a template method,we created irregular protruding microstructures of varying heights on the ionogel's surface,exploring a simple,green approach to constructing microstructured ionogels.Knitted textiles,characterized by their unique loop structure,exhibit remarkable elasticity and stretchability.Their soft and breathable nature makes them well-suited for direct contact with the skin,allowing for a comfortable wearing experience that can adapt to various body types.Consequently,the integration of ionogels with knitted electrodes into a sandwich structure of textile-based ionic skin was achieved.We characterized its morphology and composition in detail,followed by an extensive study of its sensing performance.Testing revealed that the textile-based ionic skin maintained a high sensitivity of approximately 8.39 kPa-1 within a low-pressure range(0-20 kPa),with a low hysteresis of 2.2％.Importantly,even after more than 5 000 cycles of compressive testing,the capacitive signal variations remained stable,showcasing the ionic skin's excellent dynamic monitoring capabilities.This development allows for stable and reliable monitoring of dynamic human signals,highlighting significant application potential in fields such as sports training and human-machine interaction.
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