Responsive polymer-based materials are capable of altering their chemical and/or physical properties upon exposure to external stimuli. These materials have been intensively studied over the years for a diverse range of applications, e.g., for on-demand drug delivery, tissue generation/repair, biosensing, smart coatings, and artificial muscles. Here, we review recent advances in the areas of sensing and biosensing, drug delivery, and actuators. Specific examples are given in each of these areas, and we highlight our group's work on poly(N-isopropylacrylamide)-based microgels and assemblies.

The use of stimuli-responsive polymers in sensing technologies and for actuation has garnered tremendous interest over the past few decades. This is mainly due to the myriad responsivities that these polymers can possess, e.g., responsivity to temperature, pH, biomolecules, CO₂, light, and electricity. As a result, these stimuli-responsive devices can be used to monitor human health and detect environmental analytes, for soft robotics and artificial muscles. In this review, we highlight state-of-the-art examples of the synthesis, and use of stimuli-responsive polymers in these fields that have been reported since 2016.