Membrane-type Soft Actuator Based on Transformable PMMA/PI/PDMS Framework

Abstract

As the demand for three-dimensional electronic devices increase, transformation technology from planar to three-dimensional geometry is gaining attention because well-established high performance silicon-based semiconductor manufacturing techniques are available. However, current transformation technologies face several issues, including selective transformation, self-transformation, the combination of rigid and soft materials, and both reversible and irreversible transformations. Here, this study addresses these issues by developing a membrane-type soft actuator based on a transformable PMMA/PI/PDMS framework mounting Joule heaters. To promote interfacial adhesion property between the layers, firstly the ester groups in PMMA and the amine-anchored PI undergo amide formation, secondly, amine-anchored PI and epoxy-anchored PDMS are chemically reacted. Extrusion-printed-PMMA lines reserves the residual stress and thereby irreversible contraction upon heating. The laminated PI and PDMS layers reversibly deforms under heating and cooling due to the different thermal expansion coefficients. A laminating membrane-type Joule heater enables heating a selective area without using a convection oven. The degree of transformation is adjustable by varying the PDMS thickness and annealing temperature. Electronic stability during irreversible transformation is also confirmd by monitoring no significant change in the resistance of the joule heater. In the case of reversible transformation, every annealing curvature of reversible transformation in the 1000th cycle test maintains almost the same values without resistance change before and after the cycle test. Finally, a gripper application is demonstrated by successfully implementing to grab and release objects through the stepwise irreversible and reversible transformation from a membrane-type soft actuator.