1, 2 The shape memory effect (SME) consists of recovering a permanent shape triggered by external stimuli such as heating, electromagnetic field, light, or vapor. Shape-memory polymers (SMPs) are a class of stimuli-responsive materials that are able to change shape in response to an external stimulus. 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). The fastest recovery was obtained by the 15% boron nitride actuator, which recovered the 100% of the original shape in only 8 s. Electro-responsive actuators were found extremely faster than the conventional SMPs based on external heating.
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. A thermoelectric control unit was developed to control the shape recovery of the electro-responsive actuators and provide different activation strategies. Boron nitride agglomerates were dispersed in the thiol-acrylate-epoxy layers to increase thermal conductivity and achieve faster shape-recovery. The shape-memory effect (SME) was activated by the heat dissipated by the Joule effect in the conductive track. A conductive heater, consisting of an electrically conductive silver-ink track printed on Kapton® substrate, was assembled to the SMP, taking advantage of the 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).
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