Electro-responsive shape-memory composites obtained via dual-curing processing

In this work, electro-responsive shape-memory actuators were developed by incorporating a conductive heater in a dual-curing thiol-acrylate-epoxy shape-memory polymer (SMP). A conductive heater, consisting of an electrically conductive silver-ink track printed on Kapton (R) substrate, was assembled to the SMP, taking advantage of the dual-curing processing. The shape-memory effect (SME) was activated by the heat dissipated by the Joule effect in the conductive track. Boron nitride agglomerates were dispersed in the thiol-acrylate-epoxy layers to increase thermal conductivity and achieve faster shape-recovery. A thermoelectric control unit was developed to control the shape recovery of the electro-responsive actuators and provide different activation strategies. The electrically activated SME was investigated and compared to a traditional SME based on an external heating source given by the dynamic mechanical analyzer (DMA) apparatus. Electro-responsive actuators were found extremely faster than the conventional SMPs based on external heating. The fastest recovery was obtained by the 15% boron nitride actuator, which recovered the 100% of the original shape in only 8 s. The thermoelectric controlling device provided an optimal control of the shape recovery speed based on the pulse width modulation of the heating current under the application of a low voltage (5 V).