A multi-responsive bidirectional bending actuator based on polypyrrole and agar nanocomposites

Smart actuators have recently been widely studied due to their potential applications in the fields of wearable devices, artificial muscles and microrobots. However, it is still challenging to develop smart actuators with a fast response time, large deformation, multi-stimuli response ability and programmable shape-changing capability. Here, we report a novel smart actuator, which consists of polypyrrole and agar. Due to the water absorbing ability, the photothermal effect and the protonation behavior originating from polypyrrole and agar, the resulting actuator is responsive to a variety of stimuli, including humidity, light, temperature, HCl and NH 3 gas. In addition, the actuator exhibits fast responsiveness, controllable actuation and large bending. Interestingly, two external stimuli can be combined to activate the actuator, leading to continuous shape changes in a programmable fashion. Multi-stimuli responsive actuators have opened up great opportunities in a variety of applications. As a proof-of-concept, we have demonstrated their application as a walking device with cargo transportation and delivery capabilities.