Design of multi-stimuli responsive hybrid pneumatic – magnetic soft actuator with novel channel integration

• Single stimuli responsive soft actuators have limited degrees of freedom. • Fabrication of soft actuator that can respond to multiple stimulus. • Hybrid pneumatic-magnetic soft actuator have expanded movement. • Able to achieve higher blocking force at lower power input. Smart polymeric materials based soft actuators are flexible, lightweight, and can deliver a wide range of actuations. Thus, they are ideal for applications requiring delicate and unconventional motions, such as biomedical and soft robotics. This paper reports a novel multi-stimulus responsive soft actuator that combines the advantages of pneumatic and magnetic systems to achieve multi-plane actuation behavior with high blocking forces at low power input. This novel pneumatic – magnetic (HPM) soft actuator is designed through geometric, nanoparticle alignment, and mechanical criterions. By utilizing 3D printed wires and the compliant matrix, unique micro air channels were manufactured. These distinct internal tubular structures created localized and distinctive bending paths beyond the traditional circular trajectory. Addition of Fe 3 O 4 nanoparticles under a magnetic field exhibited a decrease in stiffness of the elastomer matrix by 85%, increasing the blocking force by 3500%, and decreasing the air pressure input to achieve same degree of actuation. Furthermore, it was observed that the magnetic nanoparticles alignment within the samples enhanced the magnetic deflection and susceptibility. The HPM soft actuator demonstrated its practicability through a gripper system to lift objects greater than its initial width and 3.4 times its own mass. Multi-plane actuation was also demonstrated to complete a circuit and light up an LED. A 5 legged “star” shaped HPM soft actuator was also fabricated to exhibit the multi-stimuli response, reacting to both pneumatic and magnetic stimuli in both air and water environments. Using the advantage of the multi-plane pneumatic/magnetic actuation, such hybrid soft actuator has the capability to be utilized in biomimicking and unconventional applications where unique maneuverability is required.