Tough, Antifreezing, and Conductive Hydrogel Based on Gelatin and Oxidized Dextran

Abstract

Forming natural polymers‐based hydrogels with enhanced mechanical strength, outstanding antifreezing property and superior conductivity is still a challenge. Here, gelatin/oxidized dextran hydrogel is fabricated and it shows enhanced mechanical performance, antifreeze tolerance, and conductivity due to the synergistic interaction of ammonium sulfate and betaine. The resulting gelatin/oxidized dextran/(NH4)2SO4/betaine hydrogel exhibits high stretchability (570%), tough tensile (2.49 MPa) and compressive (46.41 MPa) fracture strength, favorable tensile (6.05 MJ m−3) and compressive (3.08 MJ m−3) toughness, antifreezing property (−30 °C) and high conductivity (2.86 S m−1). Based on the above characteristics, the hydrogel is applied for strain sensor to monitor the joints motion of human body such as finger, wrist, elbow, knee, neck, and throat. The hydrogel can maintain good mechanical performance and stable sensing signal from 25 to −30 °C. Therefore, the designed hydrogel based on natural polymers shows a huge potential for tissue engineering and biosensing under the mild or extreme environment.

Highly Robust, Sensitive, Antifreezing, and Drying-Tolerant Polyacrylamide/Gelatin/Zr4+ Hydrogels as Flexible Strain Sensors

“…As shown in Figure a,b, the first hysteresis loop was much larger than the following loops and the dissipated energy sharply reduced from 0.29 to 0.04 MJ m –3 . These results manifested that the defective metal coordination bonds fractured and triple-helix gelatin chains unwound during the loading–unloading process . Moreover, except for the first loading–unloading cycle, the remaining dissipated energy retained good stability with only a slight fluctuation, indicating the outstanding fatigue resistance of the PG-Zr 0.1 4+ hydrogel.…”

Electroactive and Stretchable Hydrogels of 3,4-Ethylenedioxythiophene/thiophene Copolymers

“…It can be concluded from the results of the mechanical experiment of the P­(EDOT- co -Th) copolymer-containing hydrogels that the higher the molar ratio of EDOT to Th, the stronger the tensile strength and the lower the elongation break tends to be. Swelling tests were carried out to determine the swelling ratio for evaluating the density of the hydrogen bonding network among the hydrogels . The higher the molar ratio of EDOT to Th, the lower was the swelling rate, indicating that the existence of EDOT could increase the crosslink density of hydrogels (Figures S7 and S8).…”

“…Swelling tests were performed according to the literature method; the equilibrium swelling ratio was calculated using eq normals normalw normale normall normall normali normaln normalg .25em normalr normala normalt normali normalo .25em ( % ) = W normalw − W 0 W 0 × 100 where W 0 and W w represent the weight of hydrogels before and after swelling in distilled water, respectively.…”

“…Swelling tests were carried out to determine the swelling ratio for evaluating the density of the hydrogen bonding network among the hydrogels. 68 The higher the molar ratio of EDOT to Th, the lower was the swelling rate, indicating that the existence of EDOT could increase the crosslink density of hydrogels (Figures S7 and S8). These findings can be supported by FT-IR and SEM studies; the experimental evidences point out that the intermolecular hydrogen bond between oxygen atoms of the EDOT and the amino groups of the AAm units may play an important role in regulating mechanical and swelling behaviors of hydrogels (Figures 3,4 and S8).…”

Significant Roles of Ions in Enhancing and Functionalizing Anisotropic Hydrogels

“…A great issue for state-of-the-art ion sensors used outdoors is their adaptability to harsh natural environments, leaving an open question of whether ion sensors are able to remain useful under harsh conditions such as high and low temperatures. − That is, advanced ion sensors are often required to show water retention capability and antifreezing properties. A solar simulator and a refrigerator are used to simulate the harsh environments for the Aniso-Ca 1.5 2+ hydrogel (Figure S17), with the isotropic hydrogel for comparison.…”