Stretchable, self‐healable, and breathable biomimetic iontronics with superior humidity‐sensing performance for wireless respiration monitoring

Abstract

Stretchable, self-healing, and breathable skin-biomimetic-sensing iontronics play an important role in human physiological signal monitoring and human-computer interaction. However, previous studies have focused on the mimicking of skin tactile sensing (pressure, strain, and temperature), and the development of more functionalities is necessary. To this end, a superior humidity-sensitive ionic skin is developed based on a self-healing, stretchable, breathable, and biocompatible polyvinyl alcohol-cellulose nanofibers organohydrogel film, showing a pronounced thickness-dependent humidity-sensing performance. The as-prepared 62.47-μm-thick organohydrogel film exhibits a high response (25,000%) to 98% RH, excellent repeatability, and long-term stability (120 days). Moreover, this ionic skin has excellent resistance to large mechanical deformation and damage, and the worn-out material can still retain its humidity-sensing capabilities after self-repair. Humidity-sensing mechanism studies show that the induced response is mainly related to the increase of proton mobility and interfacial charge transport efficiency after water adsorption. The superior humidity responsiveness is attributed to the reduced thickness and the increased specific surface area of the organohydrogel film, allowing real-time recording of physiological signals. Notably, by combining with a self-designed printed circuit board, a continuous and wireless respiration monitoring system is developed, presenting its great potential in wearable and biomedical electronics.

Multifunctional all hydrogel-based smart dressing system fabricated by a self-healing cross-linking strategy for real-time monitoring of wound temperature, strain and on-demand drug delivery

“…18,19 Among them, hydrogels are considered to be a promising material for promoting wound healing due to their similar flexibility to the native extracellular matrix (ECM), excellent biocompatibility compatible with the skin, good selfhealing and ability to provide a moist environment. [20][21][22][23][24][25][26][27][28][29][30] To date, many smart hydrogel dressings have been developed…”

“…18,19 Among them, hydrogels are considered to be a promising material for promoting wound healing due to their similar flexibility to the native extracellular matrix (ECM), excellent biocompatibility compatible with the skin, good self-healing and ability to provide a moist environment. 20–30 To date, many smart hydrogel dressings have been developed for wound management. 31,32 Various hydrogels with inherent or additional antibacterial properties have been used for inhibiting infection and preventing the chronic phase of the wound.…”

A κ-Carrageenan-Containing Organohydrogel with Adjustable Transmittance for an Antifreezing, Nondrying, and Solvent-Resistant Strain Sensor

“…Yu et al fabricated a highly ion-conductive and cellulose nanofibril (CNF)-reinforced organogel with extreme-temperature tolerance for flexible humidity sensors . Wu and co-workers successfully constructed a series of multifunctional soft gel polymers based on different biological macromolecules, which could serve as stretchable, highly sensitive, and environmentally-tolerant gas sensors with wireless operation. − Notably, κ-carrageenan (κ-CG) as a biomacromolecule is a linear sulfated polysaccharide extracted from natural seaweed and possesses superior biocompatibility, nontoxicity, and excellent gel-forming capabilities, which is also regarded as a promising material to improve the toughness of hydrogels. , For instance, Tao et al reported a tactile hydrogel sensor based on a micropyramid-patterned double-network ionic hydrogel consisting of carrageenan and PAM chains, which exhibited fascinating application prospects in flexible electronics . Additionally, previous studies have suggested that adding metal ions into hydrogels containing poly­(acrylic acid) chains is also an effective strategy to further enhance their mechanical properties. − The added metal ions can form strong coordination bond interactions with the carboxyl groups onto poly­(acrylic acid) chains, which remarkably increase the cross-linking densities of hydrogel networks and endow the resulting hydrogel with excellent stretchability and robustness.…”

3D Single‐Layer‐Dominated Graphene Foam for High‐Resolution Strain Sensing and Self‐Monitoring Shape Memory Composite

“…This significant thermoacoustic effect observed certifies that SLGF has an excellent ability to generate heat (Joule heat) and transfer heat. Compared to other types of strain or temperature sensors, such as highly-stretchable hydrogel sensors, [39][40][41][42][43] the SLGF sensors are crucially in applications that require both strain monitoring and thermal control.…”