Stimuli-Responsive Actuators
Stimuli-responsive polymers have transformed the landscape of soft actuators, with liquid crystal polymers (LCPs) standing out prominently among them. Their extraordinary features, including programmable deformation through variable alignment and the ability to exhibit large strains with rapid responses, have garnered significant attention. By incorporating photo-absorbing dyes such as azo-benzenes, LCPs become responsive to light. The combination of spatial, temporal, and non-contact actuation facilitated by light-based stimuli, along with the inherent programmability and large-strain capabilities of LCPs, establishes them as premier soft actuators.
Given the broad range of potential applications across various fields, a thorough understanding of the actuation characteristics of LCPs is crucial. This project addresses this need by developing finite element and molecular dynamics computational frameworks to simulate the real-time actuation responses of LCPs under diverse stimuli conditions. The continuum-scale computational framework, crafted using Abaqus and custom sub-routines, comprehensively models the multi-physics underlying the response of LCPs. It accounts for non-linear attenuation, self-shadowing, temperature elevation, and temperature-induced changes in isomerization. The predictions from this framework align well with experimental data for different systems, including mono/di-acrylate azo-LCPs and NIR-dye-doped LCPs. Furthermore, the framework is adeptly employed to simulate self-sustained oscillations of LCPs on hot plates at specific temperatures, shedding light on the specific conditions required for sustained oscillations.
Light-actuated deformations in azo-modified liquid crystal polymer network thin film
Molecular dynamics simulation of light-induced density changes in azo-modified liquid crystal polymer network thin film
On a molecular scale, the trans azo-molecules experience trans-cis isomerization when exposed to UV wavelengths, instigating local disorder and deformation within the Liquid Crystal Polymer (LCP). Subsequent exposure of the cis isomer to blue wavelengths prompts the azo molecules to revert to the trans state. When both UV and blue light sources are concurrently applied to azo-doped LCPs, the simultaneous occurrence of trans-to-cis and cis-to-trans isomerizations disrupts the equilibrium of the molecular network, leading to a significant reduction in density. To delve more deeply into these intricate dynamic processes, an atomistic-scale computational framework is devised to simulate isomerization dynamics and precisely identify optimal conditions for inducing density reduction. The framework is available in GitHub.
Self-sustained oscillations of thermo-responsive liquid crystal thin films on a hot plate
We have created a multiphysics computational framework employing the finite element method to model the oscillatory characteristics of LCN films placed on a heated plate.Â
Tunable three dimensional shape changes in thermo-responsive liquid crystal thin films
Inspired by the butterfly's proboscis, an innovative tapered film is fabricated and modelled. Compared with similar works in literature, the tapered film bends many times more and forms small rolls about one-eighth the size of the straight film.
We have further extended the tapering concept to fabricate a splay-nematic liquid crystal polymer network tapered actuator that can morph from a flat film to a cone, mimicking the blooming of a single petal Calla Lily flower.
