Abstract: |
Stimuli responsiveness and reversible deformation are the peculiar characteristics of liquid crystalline elastomers (LCEs) that make them as highly suitable candidates for smart devices. The liquid crystalline properties and the elasticity of the polymeric network result in responsive soft materials able to sense the environment and act in response to selected stimuli for intelligent sensors, and actuators in photonic, robotic and medical applications. The intrinsic intelligence of these materials has been investigated and exploited to fabricate millimetric optical sensors as well as a microrobotic hand. On one hand, a temperature responsive LCE actuator has been combined with a Morpho Menelaus butterfly wing in a biotic-abiotic system. In response to environmental temperature changes, the nature optimized blue structural color of the wing is tuned by the reversible deformation of the integrated LCE actuator. Two different strategies have been proposed to control the visual sensor: a macroscopic deformation of the combined system induces an iridescence variation, whereas a nanoscale contraction generates a color shift through the lamellae interspacing variation, parameter that determines the structural coloration De Bellis et al., 2020.
On the other hand, using the lithographic technique of direct laser writing, LCEs together with glassy polymers have been patterned into a micrometric design that resembles a humanoid hand. Controlling the liquid crystal elastomer alignments in the microstructure is possible to obtain four micro fingers that bend towards one single point thus mimicking the functionality of the human hand. Such microrobotic structure is therefore able to close and grab micro objects under a light stimulus. More interestingly, thanks to the opto-thermal responsiveness of LCEs, the microhand can operate even autonomously and catch colored micro-objects depending on the target optical properties Martella et l., 2017. These implementations show as a material intrinsic intelligence can be programmed and obtained in LCE based devices able to take simple autonomous decisions.
De Bellis, I., Ni, B., Martella, D., Parmeggiani, C., Keller, P., Wiersma, D.S., Li, M.H. and Nocentini, S., "Color Modulation in Morpho Butterfly Wings Using Liquid Crystalline Elastomers". Adv. Intell. Sys. 2020, 2000035.
Martella, D., Nocentini, S., Nuzhdin, D., Parmeggiani, C. and Wiersma, D.S., "Photonic microhand with autonomous action". Adv. Mater. 2017, 29(42), 1704047. |