An MEMS-based multiple electro-rheological bending actuator system with an alternating pressure source

• An MEMS-based ER bending actuator system using alternating pressure was proposed.
• New PDMS micromolding process that utilizes PVA sacrifice layers was developed.
• PDMS parts with high aspect ratios and 3-D structures were achieved by the process.
• 1.6 mm long MEMS-based ER bending actuators were successfully fabricated.
• Tip displacement of 1.1 mm with bidirectional bending motion was achieved.

This paper presents a novel MEMS-based electro-rheological (ER) bending actuator system with an alternating pressure source for micro-scale applications with multiple microactuators. The ER bending actuator system is based on rectification of alternating flows by synchronized control valves using a liquid crystal as a working fluid. It enables the number and size of supply and return pipes to be reduced. In addition, the working principle of the alternating pressure system makes all critical hydraulic components such as the pump, valves and hydraulic actuators suitable for MEMS fabrication. In this paper, the bending parts featuring high-aspect-ratio and three-dimensional structures were realized by a newly developed PDMS micromolding process which was achieved by a separation process using poly (vinyl alcohol) (PVA) sacrificial layers dissolved by water ultrasonication with proper external forces. Control valves called ER microvalves were fabricated by standard silicon micromachining and their characteristics were investigated. The fabricated 1.6-mm long ER bending actuator demonstrated bi-directional motions that achieved a displacement of 1.1 mm (radius of curvature of 1.2 mm) and a rise time of 1.1 s. In addition, the characteristics of the tip displacements vs. applied voltages are also presented. The experimental results showed that this system is promising for control systems of high power, high-speed and miniature motion with large strokes.