Shape-memory actuators manufactured by dual extrusion multimaterial 3d printing of conductive and non-conductive filaments

In this research study we present the development of geometrically complex shape-memory actuators manufactured by dual extrusion multimaterial 3D printing using both conductive composite filaments and non-conductive thermoplastic filaments. To our knowledge, dual extrusion multimaterial 3D printing is used for the first time to create active local heating zones, due to Joule effect within the conductive filament, which result completely integrated into the actuator structure, mainly made of the non-conductive filament with shape-memory properties. Manufacture is accomplished in a single printing step, which minimizes post-processing and the use of additional heating elements, such as resistors, Peltier cells or knitted or glued thermal patches, as part of the device structure is, in fact, active. The actuator geometries are designed by means of computer aided design resources and with the support of thermal finite element modeling. Validation is achieved by testing with the manufactured prototypes and by monitoring the heating and consequent shape recovery process with the support of infrared thermography. Such final testing of the developed actuators helps to assess and validate the developed actuators and to put forward some current challenges when compared with alternative approaches for the engineering of complex shape-memory actuators.