Unravelling humidity-gated, temperature responsive bilayer actuators.

By spraying liquid crystal mixtures onto stretched polyamide 6 (PA6) substrates, dual-responsive heat/humidity bilayer actuators are generated. The oriented PA6 guides the self-organization of the liquid crystal monomers into well-aligned, anisotropic liquid crystal networks. The bilayer responds to changes in the environmental relative humidity, resulting in bending of the actuator with the liquid crystal network inside the curvature. In contrast, in conditions of constant high humidity (80%RH), increasing the temperature triggers the liquid crystal network coating to bend the bilayer in the opposing direction. The dual-responsivity to changes in environmental humidity and temperature is examined in detail and discussed theoretically to elucidate the humidity-gated, temperature responsive properties revealing guidelines for fabricating anisotropic bilayer actuators.