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

Abstract

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 which different leg designs may be programmed to change the dynamics of the robot. This is just one of the many applications that this material could have, other uses include the development of sports equipment such as a deployable kayak, use on wings for glider micro aerial vehicles, among others.