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A smart ionic skin patch with on-demand detachable adhesion has been developed as human-machine interface for physiological signal monitoring. In spite of the multifunctions demonstrated by existing ionic skin, it is still difficult to distinguish different signals simultaneously. Moreover, the secondary damages to the tissues are often overlooked when the adhesive materials are removing from the wound. Herein, a multifunctional biomimetic hydrogel with temperature, mechanical, electrical, and pH response is developed. This hydrogel is designed by in situ polymerizing of hydrophilic anion monomers in a natural cationic polysaccharide to construct multifunctional biomimetic ionic channel. Due to the reversible physical cross-linked network and thermosensitivity, the mechanical properties, adhesion, and visual effect of the hydrogel can be tuned by changing hydrogen bonding density via phase transition, thus making it an excellent biosafe material for wearable device. The hydrogel is utilized as skin patch intended for monitoring physiological signals stimulated by physical and chemical changes involving pressure, temperature, pH value, and electrocardiograph. Especially, this ionic skin patch can recognize temperature change signals precisely either in broad or extremely narrow temperature range. This smart skin patch can even recognize the pressure and temperature signals in real time and differentiate the signals simultaneously.
Shi et al. (Tue,) studied this question.