Rapid Self-Recoverable Hydrogels with High Toughness and Excellent Conductivity

Hydrogels as soft and wet materials have attracted much attention in sensing and flexible electronics. However, traditional hydrogels are fragile or have unsatisfactory recovery capability, which largely limit their applications. Here, a novel hydrogen bond based sulfuric acid–poly­(acrylic acid) (PAA)/poly­(vinyl alcohol) physical hydrogel is developed for addressing the above drawbacks. Sulfuric acid serves two functions: one is to inhibit the ionization of carboxyl groups from PAA chains to form more hydrogen bonds and the other is to provide conductive ions to promote conductivity of hydrogel. Consequently, the hydrogel obtains comprehensive mechanical properties, including extremely rapid self-recovery (strain = 1, instantly self-recover; strain = 20, self-recover within 10 min), high fracture strength (3.1 MPa), and high toughness (18.7 MJ m^–3). In addition, we demonstrate this hydrogel as a stretchable ionic cable and pressure sensor to exhibit stable operation after repeated loadings. This work provides a new concept to synthesize physical hydrogels, which will hopefully expand applications of hydrogel in stretchable electronics

Rapid Self-Recoverable Hydrogels with High Toughness and Excellent Conductivity

Hydrogels as soft and wet materials have attracted much attention in sensing and flexible electronics. However, traditional hydrogels are fragile or have unsatisfactory recovery capability, which largely limit their applications. Here, a novel hydrogen bond based sulfuric acid–poly­(acrylic acid) (PAA)/poly­(vinyl alcohol) physical hydrogel is developed for addressing the above drawbacks. Sulfuric acid serves two functions: one is to inhibit the ionization of carboxyl groups from PAA chains to form more hydrogen bonds and the other is to provide conductive ions to promote conductivity of hydrogel. Consequently, the hydrogel obtains comprehensive mechanical properties, including extremely rapid self-recovery (strain = 1, instantly self-recover; strain = 20, self-recover within 10 min), high fracture strength (3.1 MPa), and high toughness (18.7 MJ m^–3). In addition, we demonstrate this hydrogel as a stretchable ionic cable and pressure sensor to exhibit stable operation after repeated loadings. This work provides a new concept to synthesize physical hydrogels, which will hopefully expand applications of hydrogel in stretchable electronics

Biocompatible Photoluminescent Silk Fibers with Stability and Durability

Exploring photoluminescent silk fibers, possessing biocompatibility as well as stable and durable fluorescent properties, is a requirement for the development of novel photoluminescent biomaterials. Herein, we fabricate photoluminescent silk fibers, TPCA@SF, via modifying an organic fluorescent molecule (5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid, TPCA) onto silk fibers, along with using quaternary ammonium salt didodecyldimethylammonium bromide (DDAB) as a color-fixing agent. The hydrogen bonds and electrostatic association among silk fibers, TPCA and DDAB, ensure the stable modification. The facile and green fabrication process is achieved in water under mild conditions without using any toxic substances. The TPCA@SF manifests the combining features of high quantum yield, fluorescence water-fastness, antiphotobleaching, good mechanical property, and biocompatibility. The strategy holds great potential for exploring various biocompatible photoluminescent substances with stability and durability

Strengthening Alginate/Polyacrylamide Hydrogels Using Various Multivalent Cations

We successfully synthesized a family of alginate/polyacrylamide hydrogels using various multivalent cations. These hydrogels exhibit exceptional mechanical properties. In particular, we discovered that the hydrogels cross-linked by trivalent cations are much stronger than those cross-linked by divalent cations. We demonstrate stretchability and toughness of the hydrogels by inflating a hydrogel sheet into a large balloon, and the elasticity by using a hydrogel block as a vibration isolator in a forced vibration test. The excellent mechanical properties of these hydrogels may open up applications for hydrogels