A multi-DOF soft microactuator integrated with flexible electro-rheological microvalves using an alternating pressure source

For advanced microrobots such as an in-pipe working microrobot with dexterous micromanipulators, a novel multi-degree of freedom (DOF) soft microactuator integrated with flexible electro-rheological microvalves (FERVs) using an alternating pressure source was proposed and developed. The concept of the proposed actuator includes a series connection of multiple one-DOF microactuator units, built-in FERVs, and an alternating pressure system. The one-DOF soft microactuator unit consists of a bending fluidic actuator part and the FERVs. The FERV made from flexible materials controls electro-rheological fluid (ERF) flow by its viscosity change with the electric field applied through fixed electrodes. The alternating pressure of the ERF is supplied with only one pipe and rectified with the synchronously on/off-controlled FERVs. The benefits of the proposed actuator are (a) compact design with built-in FERVs and the alternating pressure system, (b) multi-DOF actuator with simple structure, and (c) closed system suitable for independent microrobots. In this paper, as a basic module, a 20 mm long two-DOF soft microactuator with two actuator units was developed. Through simulation, the length ratio of the one-DOF soft microactuator units were determined. The material of the fluidic chambers was selected by fabricating and testing the bending fluidic actuator parts. Then the designed microactuator was successfully fabricated using MEMS technologies. Through experiments, the tip displacements, the response, and the output forces were clarified. The two-DOF motion was realized and the validity of the proposed actuator was confirmed. (paper)