Recently, self-healing hydrogel bioelectronic devices
have raised
enormous interest for their tissue-like mechanical compliance, desirable
biocompatibility, and tunable adhesiveness on bioartificial organs.
However, the practical applications of these hydrogel-based sensors
are generally limited by their poor fulfillment of stretchability
and sensitivity, brittleness under subzero temperature, and single
sensory function. Inspired by the fiber-reinforced microstructures
and mechano-transduction systems of human muscles, a self-healing
(90.8%), long-lasting thermal tolerant and dual-sensory hydrogel-based
sensor is proposed, with high gauge factor (18.28) within broad strain
range (268.9%), low limit of detection (5% strain), satisfactory thermosensation
(−0.016 °C–1), and highly discernible
temperature resolution (2.7 °C). Especially by introducing a
glycerol/water binary solvent system, desirable subzero-temperature
self-healing performance, high water-retaining, and durable adhesion
feature can be achieved, resulting from the ice crystallization inhibition
and highly dynamic bonding. On account of the advantageous mechanoreception
and thermosensitive capacities, a flexible touch keyboard for signature
identification and a “fever indicator” for human forehead’s
temperature detection can be realized by this hydrogel bioelectronic
device.
Electronic skin is driving the next generation of cutting-edge wearable electronic products due to its good wearability and high accuracy of information acquisition. However, it remains a challenge to fulfill the requirements on detecting full-range human activities with existing flexible strain sensors. Herein, highly stretchable, sensitive, and multifunctional flexible strain sensors based on MXene- (Ti3C2Tx-) composited poly(vinyl alcohol)/polyvinyl pyrrolidone double-network hydrogels were prepared. The uniformly distributed hydrophilic MXene nanosheets formed a three-dimensional conductive network throughout the hydrogel, endowing the flexible sensor with high sensitivity. The strong interaction between the double-network hydrogel matrix and MXene greatly improved the mechanical properties of the hydrogels. The resulting nanocomposited hydrogels featured great tensile performance (2400%), toughness, and resilience. Particularly, the as-prepared flexible pressure sensor revealed ultrahigh sensitivity (10.75 kPa-1) with a wide response range (0-61.5 kPa), fast response (33.5 ms), and low limit of detection (0.87 Pa). Moreover, the hydrogel-based flexible sensors, with high sensitivity and durability, could be employed to monitor full-range human motions and assembled into some aligned devices for subtle pressure detection, providing enormous potential in facial expression and phonation recognition, handwriting verification, healthy diagnosis, and wearable electronics.
To meet critical requirements on flexible electronic devices, multifunctionalized flexible sensors with excellent electromechanical performance and temperature perception are required. Herein, lignin-reinforced thermoresponsive poly(ionic liquid) hydrogel is prepared through an ultrasound-assisted synthesized method. Benefitting from the electrostatic interaction between lignin and ionic liquid, the hydrogel displays high stretchability (over 1425%), excellent toughness (over 132 kPa), and impressive stress loading-unloading cyclic stability. The hydrogel strain sensor presents excellent electromechanical performance with a high gauge factor (1.37) and rapid response rate (198 ms), which lays the foundation for human body movement detection and smart input. Moreover, owing to the thermal-sensitive feature of poly(ionic liquid), the as-prepared hydrogel displays remarkable thermal response sensitivity (0.217°C-1) in body temperature range and low limit of detection, which can be applied as a body shell temperature indicator. Particularly, the hydrogel can detect dual stimuli of strain and temperature and identify each signal individually, showing the specific application in human-machine interaction and artificial intelligence. By integrating the hydrogel strain sensor into a wireless sensation system, remote motion capture and gesture identification is realized in real-time.
Hydrogel is frequently used as a solid electrolyte for all solid‐state supercapacitors (SCs) because of its liquid‐like ion‐transport property and high conformability. However, due to the higher water content, the hydrogel electrolyte undergoes inevitable freezing and/or dehydration with climate change. Herein, polypyrrole/carbon all‐solid‐state SCs (PCSCs) were developed based on a hierarchical polypyrrole/carbon nanotube electrode and a highly stretchable double‐network polymer hydrogel electrolyte with LiCl/ethylene glycol as a mixed solvent. The PCSCs showed excellent electrochemical performance and cycle stability with a wide operating temperature. The specific capacitances could reach 202.2 and 112.3 mF cm−2 at current densities of 0.5 and 3.0 mA cm−2, respectively. Meanwhile, the PCSCs showed outstanding mechanical properties in maintaining a high areal capacitance under deformations of bending and tension. The excellent water retention of the device also ensured the stable electrochemical performance of PCSCs in a wide temperature range (30–80°C), which could potentially represent a reliable application in various harsh environments.
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