Conductive hydrogels have become one of the most promising materials for skin-like sensors because of their excellent biocompatibility and mechanical flexibility. However, the limited stretchability, low toughness, and fatigue resistance lead to a narrow sensing region and insufficient durability of the hydrogelbased sensors. In this work, an extremely stretchable, highly tough, and anti-fatigue conductive nanocomposite hydrogel is prepared by integrating hydrophobic carbon nanotubes (CNTs) into hydrophobically associated polyacrylamide (HAPAAm) hydrogel. In this conductive hydrogel, amphiphilic sodium dodecyl sulfate was used to ensure uniform dispersion of CNTs in the hydrogel network, and hydrophobic interactions between the hydrogel matrix and the CNT surface formed, greatly improving the mechanical properties of the hydrogel. The obtained CNTs/HAPAAm hydrogel showed excellent stretchability (ca. 3000%), toughness (3.42 MJ m −3 ), and great anti-fatigue property. Moreover, it exhibits both high tensile strain sensitivity in the wide strain ranges (gauge factor = 4.32, up to 1000%) and high linear sensitivity (0.127 kPa −1 ) in a large-pressure region within 0−50 kPa. The CNTs/HAPAAm hydrogelbased sensors can sensitively and stably detect full-range human activities (e.g., elbow rotation, finger bending, swallowing motion, and pronouncing) and handwriting, demonstrating the CNTs/HAPAAm hydrogel's potential as the wearable strain and pressure sensors for flexible devices.

Hydrogels based on supramolecular noncovalent interactions have attracted great research interest but are still limited by relatively low mechanical strength and performance deterioration at subzero temperatures because of the formation of ice crystallization. In this study, an antifreezing and mechanically strong gelatin supramolecular organohydrogel is prepared via a simple strategy of immersing a gelatin pre-hydrogel in the citrate (Cit) water/glycerol mixture solution. In the organohydrogel, a part of water molecules are replaced by glycerol, which inhibits the formation of ice crystallization even at extremely low temperature. In addition, the formation of noncovalent interactions such as the hydrophobic aggregation induced by the salting-out effect, ionic interactions between the −NH 3 + of gelatin and Cit 3− anions, and hydrogen bonding between gelatin chains and glycerol endows the organohydrogels with high mechanical strength and toughness. The supramolecular organohydrogel can maintain its mechanical flexibility even at −80 °C or be stored for a long time. Moreover, the nature of noncovalent interactions endows the organohydrogel with intriguing thermoplasticity, good healable ability, and excellent adhesive behavior at various substrate surfaces.

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Zwitterionic hydrogels exhibit eminent nonfouling and hemocompatibility. Several key challenges hinder their application as coating materials for blood-contacting biomedical devices, including weak mechanical strength and low adhesion to the substrate. Here, we report a poly(carboxybetaine) microgel reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel with excellent mechanical robustness and anti-swelling properties. The pCBM/pSB hydrogel coating was bonded to the PVC substrate via the entanglement network between the pSB and PVC chain. Moreover, the pCBM/pSB hydrogel coating can maintain favorable stability even after 21 d PBS shearing, 0.5 h strong water flushing, 1000 underwater bends, and 100 sandpaper abrasions. Notably, the pCBM/pSB hydrogel coated PVC tubing can not only mitigate the foreign body response but also prevent thrombus formation ex vivo in rats and rabbits blood circulation without anticoagulants. This work provides new insights to guide the design of pure zwitterionic hydrogel coatings for biomedical devices.

Intraperitoneal adhesions are common and serious complications after surgery. Deposition of proteins and inflammatory response on an injured cecum are the main factors resulting in the formation of adhesion. In this study, purely zwitterionic hydrogels (Z-hydrogels) are developed using thiolated poly­(sulfobetaine methacrylate-co-2-((2-hydroxyethyl)­disulfanyl)­ethyl methacrylate) [poly­(SBMA-co-HDSMA)] as the network backbone and divinyl-functionalized sulfobetaine (BMSAB) as the zwitterionic cross-linker via the thiol–ene click reaction. To improve the anti-inflammatory activity, cefoxitin sodium is loaded into Z-hydrogels (Z/C-hydrogel) to construct the physical barrier/drug system. The gelation time, mechanical behavior, and swelling ratio of the prepared Z-hydrogel can be modulated via adjusting the SBMA/HDSMA ratio in the copolymer. Moreover, they not only exhibit excellent resistance to protein and fibroblast adhesion but also show good biocompatibility and hemocompatibility. To assess its anti-adhesion effects in vivo, the Z-hydrogel is injected on the injured cecum surface using a rat model of sidewall defect-cecum abrasion. The results show that the Z-hydrogel can completely cover the irregular cecum surface and effectively suppress the formation of postoperative adhesion via reducing protein deposition and resisting fibroblast adhesion. Moreover, the introduction of cefoxitin sodium decreases the inflammatory response after surgery, thus further improving the anti-adhesion effect. Overall, we suggest that the Z-hydrogel is a promising candidate for the prevention of a postsurgical peritoneal adhesion.