No abstract

Biological tissues can accurately differentiate external mechanical stresses and actively select suitable strategies (e.g., reversible strain-stiffening, self-healing) to sustain or restore their integrity and related functionalities as required. Synthetic materials that can imitate the characteristics of biological tissues have a wide range of engineering and bioengineering applications. However, no success has been demonstrated to realize such strain-stiffening behavior in synthetic networks, particularly using flexible polymers, which has remained a great challenge. Here, we present one such synthetic hydrogel material prepared from two flexible polymers (polyethylene glycol and branched polyethylenimine) that exhibits both strain-stiffening and self-healing capabilities. The developed synthetic hydrogel network not only mimics the main features of biological mechanically responsive systems but also autonomously self-heals after becoming damaged, thereby recovering its full capacity to perform its normal physiological functions.

A self-healing hydrogel ionic conductor has been developed by combining dynamic covalent chemistry with nanofiller reinforcement and micelle crosslinking, and used for sensing of diverse human activities.

Mechanical responsiveness is prevalent in biological systems and plays an essential role in many biomechanical processes. The past two decades have witnessed enormous effort devoted to the development of biomimetic mechano-responsive hydrogels which are capable of adapting their physical and chemical properties to external mechanical stimuli. Due to the combination of tissue similarity and mechano-responsive properties, this type of hydrogel offers great advantages for diverse biomedical applications. Strain-stiffening and self-healing hydrogels duplicate the physiological properties of biological tissues, serving as promising candidates for artificial tissues, tissue scaffolds, and wound dressings. The shear-thinning property provides the hydrogels injectability, and the regional delivery contributes to minimally invasive treatment. Mechanochromic hydrogels allow the direct visualization of mechanical stress, holding great promise in biosensing and diagnosing. This review highlights the most recent developments in mechano-responsive hydrogels with various applications in the biomedical field. Different types of mechano-responsive hydrogels are introduced with focus on their responsive mechanisms, design strategies, and in vitro/in vivo performances, providing useful insights into the understanding and future research directions of mechano-responsive hydrogels with applications in biomedical engineering.