Recent advances in various stimuli-responsive hydrogels: from synthetic designs to emerging healthcare applications

With the development of broad interest in the synthesis of unique stimuli-responsive materials and their various healthcare applications, stimuli-responsive hydrogels have drawn major attention. Moreover, these hydrogels have become very prominent due to some of their special features like high water absorptivity, elasticity, flexibility, biodegradability and biocompatibility. In this review article, we have focused on the modern advances and the developments of stimuli-responsive polymeric hydrogels as well as nanogels based on recent reports. Different synthetic designs of different stimuli sensitive hydrogels/nanogels along with the physicochemical tuning of their properties have also been summarized. These involve the use of pH, light, temperature, electric fields, pressure, chemical agents, and ultrasound irradiation. From the past to the modern age, stimuli-responsive hydrogels have extensive uses in the healthcare sector: for example, for biosensing; as controlled/sustained drug carrier matrices; in tissue and bone regeneration; in bio-adhesives, haemostats, and shape-memory matrices; in actuation and in robotics. Therefore, we have tried to summarise all the properties and the efficiencies of various stimuli responsive hydrogels and nanogels, their structural designs, synthetic approaches and moreover their extraordinary benefits to the healthcare sector in this article.