Responsive polymer-based materials can adapt to their surrounding environment by expanding and shrinking. This swelling and shrinking (mechanotransduction) can result in a number of functions. For example, the response can be used to lift masses, move objects, and can be used for sensing certain species in a system. Furthermore, responsive polymers can also yield materials capable of self-healing any damage affecting their mechanical properties. In this chapter we detail many examples of how mechanical responses can be triggered by external electric and/or magnetic fields, hygroscopicity, pH, temperature, and many other stimuli. We highlight how the specific responses can be used for artificial muscles, self-healing materials, and sensors, with particular focus on detailing the polymer response yielding desired effects.