Design and manufacturing of thermal actuators using 3D and screen printing

Advancements in structural electronics and 3D printing bring new opportunities in the design and manufacturing of
thermal actuators. In this paper, we present the design of a thermal bilayer actuator and two methods for manufacturing
it. The actuators consists of 4 part(s): a holder, a flat panel, a thicker rim and silver traces on the panel and rim.
Actuation is achieved by Joule heating of the silver traces resulting, in thermal expansion of the panel. The function of
the rim is twofold: firstly it creates a thermal separation between the hot and cold parts and, secondly, it shifts the
neutral line to create a larger bending moment. The holder, panel and the rim were 3D printed using a polylactic acid
(PLA) filaments whereas the printing of the silver traces was either integrated in the 3D printing process or added later
by a screen printing step. In the experiment, actuator strips of 60 mm long showed controlled and reversible bending
with tip displacements of typically 10 mm and a maximum actuation force of 0.043 N (9 times its weight). To show the
effectiveness and potential of the actuators we made two types of demonstrators. We created a 15 cm human figure
which could bend its arms, legs and body and we created an animal like robot which could slowly move forward.