Highly affordable electrothermal actuators based on an embedded Cu microheater with a high-resolution pattern

Abstract

Herein, we present an affordable, a highly size- and shape-diverse high-resolution microheater for efficiently and position-selectively heating soft electrothermal actuators. The microheater was readily manufactured in large quantities by photolithographically etching a copper layer laminated with a polyimide (PI) sheet. Electrothermal actuators were fabricated by spin coating thermally expandable polydimethylsiloxane (PDMS) onto the surface of a patterned Cu (p-Cu) heater. The line-pattern dimensions of the p-Cu heater were optimized for uniform heating, after which it was used to prepare PDMS/p-Cu/PI devices. A 20 × 5 mm standard actuator typically exhibited a large bending curvature of 1.4 cm−1 at a low voltage of 2.25 V with a response time of approximately 10 s. Furthermore, we verified the feasibility of fabricating a scaled-down actuator with a critical dimension of 50 μm and a complicated device with multiple independent deformation locations on a single substrate. The miniaturized actuator exhibited a lower bending curvature than the standard device at a higher input electrical power density when heated to the same temperature. This behavior was quantitatively interpreted using the coefficient of natural convection through simulations using finite element analysis. Biomimetic demonstration devices, such as a flower-like actuator and a biomimetic hand, were successfully prepared using a p-Cu heater designed to heat multiple user-defined positions, and their normal operations were experimentally confirmed.