Search

Recently, soft electronics have attracted significant attention for various applications such as flexible devices, artificial electronic skins, and wearable devices. For practical applications, the key requirements are an appropriate electrical conductivity and excellent elastic properties. Herein, using the cyano-silver complexes resulting from coordination bonds between the nitrile group of poly(styrene-co-acrylonitrile) (SAN) and Ag ions, a self-healing elastomer demonstrating electrical conductivity is obtained. Because of these coordination complexes, the Ag-SAN elastomer possesses elasticity, compared with pristine SAN. The fracture strain of the Ag-SAN elastomers increased with the amount of added Ag ions, reaching up to 1000%. Additionally, owing to the presence of reversible coordination bonds, the elastomer exhibits self-healing properties at room temperature and electrical conductivity, thereby improving the possibility of its utilization in novel applications wherein elastic materials are generally exposed to external stimuli.

Multifunctional and thermoresponsive hydrogels can be used as soft materials in various medical applications, such as beauty devices, drug delivery, and near-infrared (NIR) lasers. In this study, methylcellulose (MC) composite hydrogels containing tannic acid (TA) and Fe3+ were prepared via a simple, fast process. The MC composite hydrogel contains hydrogen bonds between the MC polymer and TA and coordination bonds between TA and Fe3+, without losing the reversible thermogelation properties of the MC polymer. The gelation rates and mechanical properties of the MC composite hydrogel were controlled by varying its TA and Fe3+ contents. In particular, the hydrogel with a TA–Fe chelating complex showed an excellent photothermal effect, indicating its potential application in cosmetic beauty devices. It also exhibited UV-blocking, antioxidant, and antibacterial properties owing to the multifunctional TA. The facile processing of these MC/TA/Fe hydrogels provides new opportunities for biomedical applications and beauty devices employing NIR laser therapy.

Self-healing, thermo-responsive hydrogels have received increasing attention for tissue engineering, drug delivery, and cosmetic applications. Here, a thermo-responsive hydrogel with self-healing properties was prepared from methylcellulose (MC) and a water-soluble chitosan oligomer (CHI-O). First, dialdehyde methylcellulose (DAMC) derivative was synthesized from MC via periodate oxidation, and its rheological behavior was investigated according to the degree of oxidation. Next, dual-crosslinked DAMC/CHI-O copolymer hydrogels were obtained via Schiff base formation between the aldehyde group of DAMC and the amino group of CHI-O. These hydrogels were chemically linked by imine bonds and physically linked through hydrophobic interactions originating from MC. Based on rheological and compression tests, the gelation rate, mechanical properties, and self-healing properties of the copolymer hydrogels are compared with those of the MC hydrogel. Finally, the release of model compounds (adenosine and l-ascorbic acid) from the DAMC/CHI-O copolymer hydrogel was studied as a preliminary test for cosmetic applications.

Thermo-sensitive methylcellulose (MC) hydrogel has been widely used as a scaffold material for biomedical applications. However, due to its poor mechanical properties, the MC-based hydrogel has rarely been employed in 3D bioprinting for tissue engineering scaffolds. In this study, the dual crosslinkable tyramine-modified MC (MC-Tyr) conjugate was prepared via a two-step synthesis, and its hydrogel showed excellent mechanical properties and printability for 3D bioprinting applications. The MC-Tyr conjugate formed a dual-crosslinked hydrogel by modulating the temperature and/or visible light. A combination of reversible physical crosslinking (thermal crosslinking) and irreversible chemical crosslinking (photocrosslinking) was used in this dual crosslinked hydrogel. Also, the photocrosslinking of MC-Tyr solution was facilitated by visible light exposure in the presence of biocompatible photoinitiators (riboflavin, RF and riboflavin 5'-monophophate, RFp). The RF and RFp were used to compare the cytotoxicity and salting-out effect of MC-Tyr hydrogel, as well as the initiation ability, based on the difference in chemical structure. Also, the influence of the printing parameters on the printed MC hydrogel was investigated. Finally, the cell-laden MC-Tyr bioink was successfully extruded into stable 3D hydrogel constructs with high resolution via a dual crosslinking strategy. Furthermore, the MC-Tyr scaffolds showed excellent cell viability and proliferation.