Remotely and Sequentially Controlled Actuation of Electroactivated Carbon Nanotube/Shape Memory Polymer Composites

4D printing technology is known as the combination of 3D printing technology and stimulus-responsive materials. 4D printed conductive filler/shape memory polymer composites have tremendous potential in the development of remotely and sequentially controlled smart devices. This work focuses on the temperature dependent volume resistivity, Joule-heating induced temperature distribution, and electroactivated shape memory behavior of 4D printed carbon nanotube (CNT) reinforced polylactic acid (PLA) under an applied DC voltage. The variation of volume resistivity of CNT/PLA composites with temperature can be attributed to matrix shrinkage and CNT contact resistance change. Enhanced electroactivated shape recovery property is demonstrated through the optimization of printing speed, layer thickness, and raster angle. Furthermore, compared to the 0 degrees specimen, the 0 degrees/90 degrees specimen has higher degree of homogeneity in temperature distribution and faster recovery process. Finally, remotely and sequentially controlled shape memory behavior of a three-pronged device is demonstrated. The above results will provide a knowledge base for future optimal design of selectively and sequentially controlled actuators.