Topologically Engineered Strain Redistribution in Elastomeric Substrates for Dually Tunable Anisotropic Plasmomechanical Responses.

The prompt visual response is considered to be a highly intuitive tenet among sensors. Therefore, plasmomechanical strain sensors, which exhibit dynamic structural color changes, have recently been developed by using mechanical stimulus-based elastomeric substrates for wearable sensors. However, the reported plasmomechanical strain sensors either lack directional sensitivity or require complex signal processing and device design strategies to ensure anisotropic optical responses.

Steerable and Agile Light-Fueled Rolling Locomotors by Curvature-Engineered Torsional Torque.

On-demand photo-steerable amphibious rolling motions are generated by the structural engineering of monolithic soft locomotors. Photo-morphogenesis of azobenzene-functionalized liquid crystal polymer networks (azo-LCNs) is designed from spiral ribbon to helicoid helices, employing a 270° super-twisted nematic molecular geometry with aspect ratio variations of azo-LCN strips. Unlike the intermittent and biased rolling of spiral ribbon azo-LCNs with center-of-mass shifting, the axial torsional torque of helicoid azo-LCNs enables continuous and straight rolling at high rotation rates (≈720 rpm).

Light-driven complex 3D shape morphing of glassy polymers by resolving spatio-temporal stress confliction.

Programmable 3D shape morphing of hot-drawn polymeric sheets has been demonstrated using photothermal local shrinkage of patterned hinges. However, the hinge designs have been limited to simple linear hinges used to generate in-plane local folding or global curvature. Herein, we report an unprecedented design strategy to realize localized curvature engineering in 3D structures employing radial hinges and stress-releasing facets on 2D polymeric sheets.

Highly enhanced voltage holding property for low-frequency-driven fringe-field switching liquid crystal mode by charge-trapping effect of carbon-nanotube-doped surface.

We herein propose a multiwalled carbon nanotube (MWCNT) doping method into liquid crystal (LC) alignment polyimides (PIs) with low resistivity for resolving both issues of voltage holding and image sticking in low-frequency-driven fringe-field switching (FFS) LC modes using negative dielectric LCs (n-LCs). By utilizing strong ion trapping ability of MWCNTs, the FFS n-LC cell aligned by low resistivity PIs with 0.05 wt% MWCNT doping exhibited an excellent voltage holding ratio of 99% under an extremely low operation frequency of 0.

Physical model for temperature-dependent dielectric properties of anisotropic nematic liquid crystals.

We derived a new analytic physical model for describing the temperature-dependent dielectric permittivities εe(T) and εo(T) in anisotropic mesophase molecules of nematic liquid crystals (NLCs). These temperature-dependent dielectric properties of NLCs could be explained by a six-parameter dielectric permittivity model, where the analytic dielectric permittivity curves of εe(T), εo(T), and Δε(T) from the model using the six parameters ε*, Aε, Bε, (Δε)o, λε, and T* showed excellent agreement with experimental data. The six-parameter dielectric permittivity model was compared to the conventional four-parameter refractive index model.

Transient flickering behavior in fringe-field switching liquid crystal mode analyzed by positional asymmetric flexoelectric dynamics.

We analyzed a transient blinking phenomenon in a fringe-field switching liquid crystal (LC) mode that occurred at the moment of frame change even in the optimized DC offset condition for minimum image flicker. Based on the positional dynamic behaviors of LCs by using a high-speed camera, we found that the transient blink is highly related to the asymmetric responses of the splay-bend transitions caused by the flexoelectric (FE) effect. To remove the transient blink, the elastic property adjustment of LCs was an effective solution because the FE switching dynamics between the splay-enhanced and bend-enhanced deformations are highly dependent on the elastic constants of LCs, which is the cause of momentary brightness drop.

Tilted Orientation of Photochromic Dyes with Guest-Host Effect of Liquid Crystalline Polymer Matrix for Electrical UV Sensing.

We propose a highly oriented photochromic dye film for an ultraviolet (UV)-sensing layer, where spirooxazine (SO) derivatives are aligned with the liquid crystalline UV-curable reactive mesogens (RM) using a guest-host effect. For effective electrical UV sensing with a simple metal-insulator-metal structure, our results show that the UV-induced switchable dipole moment amount of the SO derivatives is high; however, their tilting orientation should be controlled. Compared to the dielectric layer with the nearly planar SO dye orientation, the photochromic dielectric layer with the moderately tilted dye orientation shows more than seven times higher the UV-induced capacitance variation.