Manufacturing a Soft Actuator/sensor Integrated Structure Via Multi-Material Direct Writing Processes Technology

This paper describes a new actuator/sensor integrated structure fabricated via direct writing technique in which ionic polymer–metal composites (IPMCs) are used for actuators, and carbon nanotubes (CNTs) doped in polydimethylsiloxane (PDMS) were used for the sensors. First, we developed Nafion inks and CNT-PDMS composite inks with rheological properties tailored for direct writing. CNT-PDMS composite inks with a 4 wt% CNT concentration were three-dimensionally-printed in a Nafion structure to create an IPMC actuator structure; the CNT-PDMS composite was fabricated into a large array of strain sensors that were able to measure the bending deformation of the IPMC. A CNT-PDMS scaffold structure was semi-embedded in the Nafion structure via direct writing using CNT-PDMS composite inks with a 7 wt% CNT concentration to sense the external pressure and temperature of the IPMC actuator. Palladium and gold electrodes were applied on the surfaces of the Nafion/CNT-PDMS structure through an electroless plating and electroplating process, which enabled the three-dimensionally-printed Nafion/CNT-PDMS integrated structure to form an IPMC/CNT-PDMS integrated structure that could be actuated by voltage signals. The actuating/sensing integrated performances were tested to determine their feasibility and for using direct writing to create a smart structure that had both actuator and sensor functions and that could be used in a wide range of fields, such as micro-robotics, biomedicine, and medical science.