Peixin He

Flexible and conductive hydrogel sensors have great potential for applications in wearable and implantable devices, electronic skin and healthcare diagnosis. However, it remains a great challenge to develop an integrated tough hydrogel sensor combining stretchability, adhesiveness, self-healing ability and high sensitivity via a simple, fast and economical approach for multi-field applications. In this work, we designed a multifunctional composite self-adhesive conductive hydrogel by using chitosan (CS), tannic acid (TA) and polyacrylic acid (PAA), and ionic cross-linker Al³⁺. The synergistic multiple and reversible coordination bonds and hydrogen bonds in the matrix lead to a combination of high stretchability, rapid self-recovery, great anti-fatigue and rapid self-healing properties of the tough hydrogel. Additionally, the ionic gels displayed durable and repeatable adhesiveness ascribed to the presence of catechol groups from TA, which can adhere directly on human skin without residuals and inflammatory responses. Furthermore, our ionic hydrogel sensors exhibited a broad strain window (0–1400%) and demonstrated brilliant stretching sensitivity (gauge factor as high as 12.2), and it displayed stable sensing performance for repeated real-time monitoring of both large and subtle deformation (e.g. knee joint motions, breathing modes, and even the slight pulse changes in different motion states). This work provides a feasible method to construct self-adhesive and self-healing hydrogel sensors with high sensitivity and a large-range detection capacity and paves a way for versatile applications in electronic skin, healthcare monitoring and medical electrodes.

In this study, a novel KGM-based superabsorbent polymer KGM-g-poly-(acrylic acid-co-acrylamide-co-N,N'-dimethyl-N-ethylmethacryloxylethylammoniumbromide) (KAAD) was prepared, which was obtained by the free radical grafting solution polymerization of acrylamide (AM), acrylic acid (AA) and N,N'-dimethyl-N-ethylethacryloxylethylammonium bromide (DMAEA-EB) onto konjac glucomannan (KGM) with of potassium persulfate (K₂S₂O₈) as initiator and N,N'-methylenebisacrylamide (MBA) as crosslinker. The groups of AA, AM and DMAEA-EB grafted on KGM were detected by infrared spectroscopy (FTIR). The effects of the reaction conditions (including an initiator dosage, AA and AM mass ratio, and a reaction temperature, etc.) on the grafting degree and grafting efficiency were investigated by a gravimetric method. The maximum grafting degree and grafting efficiency of the obtained graft polymer in the experiment were 71.51 and 89.90%, respectively. The effects of crosslinking agent and GD on water absorption were explored. And all of the experimental data show that the water absorption ratio of the KAAD resin exceeds 527.00 g/g under each optimal reaction conditions. Therefore, KAAD can be widely used as a functional material in pharmaceutics, textiles, construction and other fields due to its excellent superabsorbent properties.

Lack of sufficient tumor penetration of the current nanomedicines is a major reason limiting their clinical success in cancer therapy. In this work, we aimed at the development of a novel biodegradable nanoplatform for the selective and controlled delivery of anticancer agents, with improved tumor permeability and the ability to release ultrasmall nanovesicles in the tumor microenvironment. To this end, positively charged nanogels were obtained through the double-crosslinking of chitosan with an ionic physical gelator and a disulfide-containing chemical crosslinker. After conjugation to an anionic oligomer, the cationic nanogels were transformed into negatively charged nanocarriers (CTCP), enabling effective encapsulation of the cationic anticancer agent doxorubicin (DOX) to generate a biodegradable nanomedicine (DOX@CTCP). DOX@CTCP could maintain sustained DOX release and decreased DOX toxicity. Upon arrival at the tumor tissue, the reductive and lysozyme-high microenvironment drives the cleavage of the nanomedicine to release DOX-carrying nanoblocks of smaller size, which together with their acidic-protonable feature achieves an effective therapeutic delivery into cancer cells. The nanomedicine described here showed excellent biocompatibility/biosafety and enhanced in vivo antitumor efficacy.

To date, various hydrogels have been manufactured for wearable sensors, but the simultaneous realization of optical transparency, remarkable mechanical properties, excellent sensing properties and anti-freezing features by using cheap raw materials and an easy synthesis process remains challenging. Here, high performance PVA/glycerol/NaCl (PGN) ionic hydrogel sensors were facilely manufactured to overcome these challenges. The proposed hydrogel sensors were fabricated by physically mixing the biocompatible poly(vinyl alcohol) and nontoxic glycerol in water as the gel matrix followed by soaking in saturated NaCl aqueous solution. The resulting PVA/glycerol/NaCl hydrogels exhibited good transparency (>88%), favorable stretchability (570.7%), outstanding mechanical strength (3.1 MPa), and high toughness (8.65 MJ m⁻³). Meanwhile, the PGN ionic hydrogel sensors displayed excellent stretching sensitivity with a gauge factor of 4.01, and it could repeatedly and stably detect accurate electrical signals under both large strains and subtle strains. Furthermore, our hydrogel sensors were endowed with anti-freezing features on account of the presence of both glycerol and NaCl, and the sensors could still maintain good mechanical and strain-sensitive performance at a low temperature (−20 °C). Based on the above characteristics, the biocompatible PGN hydrogel sensors could be employed as wearable devices to detect various human motions (e.g. finger, wrist, elbow, and knee joints) at room temperature and low temperature. Therefore, the as-prepared hydrogels show promising potential as high-performance wearable strain sensors for practical applications in biomimetic prostheses and human activity monitoring systems.

Creating load‐bearing hydrogels with superior mechanical strength and toughness is of vital importance for promoting the development of polymer hydrogels toward practical applications. Herein, a type of composite hydrogel is facilely fabricated employing simple and effective UV irradiation one‐pot method by introducing cheap and available nanosilica sol into hydrophobic association poly(acrylamide–lauryl methacrylate) (HAPAM gels). Composite hydrogels exhibit enhanced mechanical strength (compression stress reaching 4.4 MPa) and toughness (compression hysteresis energy achieved is 151.15 kJ m⁻³) compared to HAPAM gels. Composite hydrogels also demonstrate rapid self‐recovery behavior (95.91% stress recovery and 92.19% hysteresis energy recovery after restoration for 15 min, respectively) and favorable fatigue‐resistant ability without the help of external stimuli at room temperature based on the cyclic loading–unloading compression measurements. The simple and effective design strategy may help the development of hydrogel materials toward practical applications for soft sensors, tissue engineering, and actuators.