Hydrogel-based sensors serve as an ideal platform for developing personalized wearable electronics due to their high flexibility and conformability. However, the weak stretchability and inferior conductivity of hydrogels have severely restricted their large-scale application. Herein, a natural polymer-based conductive hydrogel integrated with favorable mechanical properties, good adhesive performance, and excellent fatigue resistance was fabricated via interpenetrating tannic acid (TA) into a chitosan (CS) cross-linked network in an acidic aqueous solution. The hydrogel was composed of a regular hierarchical porous structure, which was built by the hydrogen bonding between TA and CS. In addition, the hydrogels exhibited adjustable mechanical properties (maximum yield stress of 7000 Pa) and good stretchability (strain up to 320%). Benefiting from the abundant catechol groups of TA, the proposed hydrogels could repeatedly adhere to various material surfaces and could be easily peeled off without residue. Moreover, the hydrogel exhibited stable conductivity, high stretching sensitivity (gauge factor of 2.956), rapid response time (930 ms), and excellent durability (>300 cycles), which can be assembled as a strain sensor to attach to the human body for precise monitoring of human exercise behavior, distinguishing physiological signals, and recognizing speech. Furthermore, the prepared hydrogels also exhibited stable sensing performance to temperature. As a result, the hydrogels exhibited dual sensory performance for both temperature and strain deformation. It is anticipated that the incorporation of strain sensors and thermal sensors will provide theoretical guidance for developing multifunctional conductive hydrogels and pave a way for the versatile application of hydrogel-based flexible sensors in wearable devices and soft actuators.

Due to the unique flexibility and modifiability of hydrogels, hydrogel-based wearable sensors have drawn tremendous attention. However, traditional hydrogels rigidify or dehydrate at extreme temperatures because their included water freezes or evaporates, which greatly impedes the development and practical application of the hydrogel-based wearable sensor. Herein, a temperature-tolerant organohydrogel with self-healing properties, adhesiveness, plasticity, and high stretchability was designed by introducing the specific base pairs, adenine (A) and thymine (T), into the polyacrylamide network in a water–glycerol (Gly) binary solvent. The gelation process was mainly driven by the covalent cross-linking and the complementary base pairing of the double helix structure of DNA. The prepared organohydrogels exhibited a tensile strength of 35 kPa, a toughness of 667 kJ m–3, and were highly flexibile with a rupture elongation of 3870%. Moreover, the organohydrogel demonstrated an excellent adhesive performance toward diverse organic and inorganic substrates. The organohydrogel displayed a maximum peeling force and adhesion strength of organohydrogel to filter paper of 149 and 122 kPa, respectively. In addition, the organohydrogel presented a rapid self-healing efficiency, long-term moisture retention, and good conductivity, even at subzero temperatures (−20 °C), and can be assembled as a dual strain and thermal sensor to realize the dual-sensing. The organohydrogel strain sensor exhibited a higher sensing sensitivity [gauge factor (GF) = 11.99] over a broad strain range (∼660%) and long-term durability (>135 cycles) and can be attached to the human body to monitor human motion in real-time. Significantly, the organohydrogel still maintained its high strain sensitivity (GF = 9.76) even at a lower temperature. We envisage that this study will provide a theoretical guidance for the design and development of multifunctional conductive hydrogels with antifreezing and antidrying properties and extend the application of the hydrogel-based sensor in electronic skin, flexible control panel, wearable devices, and health monitoring in extreme environments.