Light-triggered reversible phase transition of non-photoresponsive PNIPAm for remote-controlled smart objects

Poly( N -isopropylacrylamide) (PNIPAm) is widely used for smart materials and devices owing to its thermoresponsiveness. Here we demonstrate how PNIPAm can be geared to show reversible phase transition in response to light rather than temperature through a simple signal transformation strategy. This strategy does not require the polymer to be tediously modified with any photoresponsive moieties, offering a new approach towards remote-controlled smart objects. Our concept is achieved using a photoacid and simple PNIPAm-based copolymers. Upon switching on/off light, the photoacid releases/captures a chemical signal which can reversibly change the lower critical solution temperature (LCST) of the copolymers, thereby resulting in a fast (<0.5 min) and reversible phase transition of the copolymer without changing the ambient temperature. Thereon, a series of light-controlled dynamic patterns and conceptually smart soft actuators composed of the copolymers are fabricated. Such a signal transformation strategy enabling PNIPAm photoresponsiveness may boost the development of new non-contact smart objects with adaptive responsiveness.