High-Sensitivity Flexible Sensor Based on Biomimetic Strain-Stiffening Hydrogel

Abstract

Recently, flexible wearable and implantable electronic devices have attracted enormous interest in biomedical applications. However, current bioelectronic systems have not solved the problem of mechanical mismatch of tissue–electrode interfaces. Therefore, the biomimetic hydrogel with tissue-like mechanical properties is highly desirable for flexible electronic devices. Herein, we propose a strategy to fabricate a biomimetic hydrogel with strain-stiffening property via regional chain entanglements. The strain-stiffening property of the biomimetic hydrogel is realized by embedding highly swollen poly­(acrylate sodium) microgels to act as the microregions of dense entanglement in the soft polyacrylamide matrix. In addition, poly­(acrylate sodium) microgels can release Na+ ions, endowing hydrogel with electrical signals to serve as strain sensors for detecting different human movements. The resultant sensors own a low Young’s modulus (22.61–112.45 kPa), high nominal tensile strength (0.99 MPa), and high sensitivity with a gauge factor up to 6.77 at strain of 300%. Based on its simple manufacture process, well mechanical matching suitability, and high sensitivity, the as-prepared sensor might have great potential for a wide range of large-scale applications such as wearable and implantable electronic devices.

Self-healing liquid metal hydrogel for human–computer interaction and infrared camouflage

“…The GF value of LM hydrogel-1.0 is about 3.42 in the strain range of 0-500%, and the GF value reaches 7.21 after the strain exceeds 500%, as shown in Fig. 4c, which is superior to most of reported hydrogel sensors 30,41,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] (Fig. 4f).…”

Synthetic strain-stiffening hydrogels towards mechanical adaptability

“…Hence, the implementation of mechanical matching relies on imparting non-linear mechanical responsiveness and further tuning the strain-stiffening properties. Indeed, strainstiffening hydrogels have distinct advantages with improved performances including forming high compliance between wearable devices and skin, [37][38][39] adapting to in vivo tissue growth as morphing devices to make a comfortable interface, and controlling the expression of various genes like switching the differentiation of stem cells. For example, devices mounted on strain-stiffening substrates exhibit high compliance to adjacent tissues at small strain and enhanced strain-limiting ability at large deformation.…”

Fabrication of a High-Strength, Tough, Swelling-Resistant, Conductive Hydrogel via Ion Cross-Linking, Directional Freeze-Drying, and Rehydration

“…In recent years, conductive hydrogels have been widely used in artificial skins, − flexible sensors, , and tissue engineering. ,− But the applications of traditional conductive hydrogels are largely limited because of their poor mechanical properties. Many approaches have been explored to improve the mechanical properties of the hydrogel, such as dual-network hydrogels, , nanocomposite hydrogels, − topological hydrogels, , and non-covalent cross-linked hydrogels. , Liu and colleagues introduced cellulose nanocrystals into the quaternary ammonium xylan hydrogel to prepare a cellulose nanocrystalline composite hydrogel.…”