Instabilities induced by Light in Liquid Crystal Cells with a Photo-Responsive Substrate

Light-induced instabilities in photo-oriented liquid crystal cells

In a planar liquid crystal sample sandwiched between a photosensitive and a reference plate instabilities occurred, when the cell was illuminated from the reference side. The instabilities were induced both by polarized white light source and monochromatic laser beams. Static and dynamic regimes were found; for laser irradiation dynamic instability was found only in a range of polarization directions. A model, developed for monochromatic excitation, predicts that at certain thicknesses dynamic instability is forbidden. Experiments on a wedge-like cell confirmed this conclusion.

Laser-induced instabilities in liquid crystal cells with a photosensitive substrate

Liquid crystal layers sandwiched between a reference plate and a photosensitive substrate were investigated. We focused on the reverse geometry, where the cell was illuminated by a laser beam from the reference side. In planar cells instabilities occurred, static and dynamic ones, depending on the angle between the laser polarization and the director orientation on the reference plate. In cells where the molecules were aligned along the normal of the reference plate, dynamic pattern was observed at all angles of polarization. A simple model based on a photo-induced surface torque gives account…

聚合物凝胶中的光开关交联：溶胀过程中对表面起皱和网络松弛的影响

Photo-Switchable Cross-Linking in Polymer Gels: Effects on Surface Creasing and Network Relaxation during Swelling

本文针对香豆素交联凝胶网络级力学响应不明的问题，设计了含永久性共价和动态香豆素交联的PEG水凝胶，通过特定波长紫外光原位调节交联，揭示其对力学性能和表面起皱的影响，为自适应水凝胶提供设计原则。

利用光响应手性液晶环境动态控制活性液滴

Dynamic control of active droplets using light-responsive chiral liquid crystal environment

本文提出利用光响应胆甾相液晶环境控制细菌活性液滴运动方向，通过光致螺距和手性变化实现液滴轨迹的非接触式动态重定向。

Light-induced swirling and locomotion

Photomechanical liquid crystal elastomers (LCEs) are responsive polymers that can convert light directly into mechanical deformation. This unique feature makes these materials an attractive candidate for soft actuators capable of remote and multi-mode actuation. In this work, we propose a three-dimensional multi-scale model of the nonlinear and nonlocal dynamics of fibers of photomechanical LCEs under illumination. We use the model to show that a pre-stressed helix-like fibers immersed in a fluid can undergo a periodic whirling motion under steady illumination. We analyze the photo-driven spat…

Liquid-crystal-based topological photonics

Topological photonics harnesses the physics of topological insulators to control the behavior of light. Photonic modes robust against material imperfections are an example of such control. In this work, we propose a soft-matter platform based on nematic liquid crystals that supports photonic topological insulators. The orientation of liquid crystal molecules introduces an extra geometric degree of freedom which in conjunction with suitably designed structural properties, leads to the creation of topologically protected states of light. The use of soft building blocks potentially allows for rec…

Light-controlled aggregation and gelation of viologen-based coordination polymers

Ditopic bis-(triazole-pyridine)viologens are bidentate ligands that self-assemble into coordination polymers. In such photo-responsive materials, light irradiation initiates photo-induced electron transfer to generate pi-radicals that can self-associate to form pi-dimers. This leads to a cascade of events: processes at the supramolecular scale associated with mechanical and structural transition at the macroscopic scale. By tuning the irradiation power and duration, we evidence the formation of aggregates and gels. Using microscopy, we show that the aggregates are dense polydisperse micron siz…