Active control of 4D prints: Towards 4D printed reliable actuators and sensors

[Display omitted] •The Shape Memory Effect (SME) of the 4D printed SMPC was activated via resistive (or Joule) heating by using a graphene based thermoplastic material embedded in a SMP surrounding matrix, which has not been done before.•A feedback control unit was developed to characterize the heating profile within different geometries (unit cells) of the proposed Shape Memory Polymer Composite (SMPC). The unit accounts at all times for changes in resistance due to temperature or strain.•The proposed technology can be used to design actuators of intricate geometries as it possesses an embedded material that can measure changes in strain and also activate its motion. It can be especially useful in many fields from sports equipment, i.e. a deployable Kayak, to other applications in robotics such as reconfigurable legs on crawling robots, and origami robotics. The viability of using Shape Memory Polymers (SMP), and their composites, as sensors and actuators has tremendously increased over the years as a result of the new emerging knowledge and techniques related to multifunctional composite materials science and additive manufacturing. The present study proposes the use of Extrusion Based Additive Manufacturing (EBAM, a.k.a. Fused Filament Fabrication (FFF)) to create a Shape Memory Polymer Composites (SMPC) that is electrically activated. The presented work investigates SMPC's motion trigger by a voltage application via studying a unit cell. This unit cell can be printed consecutively in the thickness or width direction to produce a large repetitive structure and satisfy dimensional requirements. A control unit was designed and manufactured specifically for this SMPC. The developed controller regulates power input to the composite in order to characterize the material's heating behaviour despite variations in resistance caused by changes in strain or temperature during the activation and use of the 4D printed SMPC. Different geometries of unit cells were analyzed to describe heat dissipation within the SMPC. The proposed technology enables exciting possibilities for 4D printed materials. As an example, the aforementioned resistance measurements of the proposed system can be used to correlate change in strain that has occurred in the SMPC during the recovery process, like a structural health monitoring system. The proposed technology has the potential to manufacture any intricate geometry of an actuator or sensor, such as the leg of a crawling robot; in whi