S. Bae, Y. Wook Noh, D.-S. Park, M.H. Song, S.-W. Choi, Development of coloured perovskite solar cells using cholesteric helicoidal superstructures. Nano Energy, 93, (2022), 106801.
In this paper, the authors developed the first coloured perovskite solar cell (PeSC) which consists of liquid crystalline cholesteric phase based reflective filters (ChRFs) instead of those based on metals or oxides. The reason for this choice is the easy modulation of properties such as reflective wavelength, bandwidth and reflectance of PeSCs using ChRFs. For instance, by tuning chiral dopant contents, the hue, which is affected by the reflective wavelengths, can be modulated. Furthermore, the power conversion efficiency, which is affected by the reflective bandwidth, can be modulated by tuning the host liquid crystal molecule’s birefringence. Reflectance affects chromaticity, which can be manipulated by changing the optical design of the ChRF. What makes ChRFs suitable candidates for building large and flexible PeSCs is the fact that they are made using organic components and wet processes.
R.S. Hendley, L. Zhang, M.A. Bevan, Design rules for 2D field mediated assembly of different shaped colloids into diverse microstructures. 18, (2022), 9273–9282.
Multifunctional particle-based materials and devices have an array of potential applications such as in display and printing technologies. However, achieving these ordered microstructures is still a difficult challenge. In this paper, the authors present design rules to assemble a variety of different shaped colloidal particles into 2D amorphous, liquid crystalline and crystalline microstructures using AC electric field. The shapes include squares, ellipses, disks, and rectangles, all of which have different anisotropies and corner curvatures. These differences play a crucial role in determining the number and type of resulting microstructures. Additionally, positional and orientational order of the colloidal particles is controlled via AC field induced dipolar interactions. Using particle tracking and dipolar interactions, microstructural states are determined. The study showcases how field conditions and particle choice allow for kinetically viable routes that enable the assembly of liquid crystal structures like nematic, tetratic and smectic as well as crystals with stretched 4- and 6-fold symmetry.
C. Meng, J.S. Wu, I.I. Smaljukh, Topological steering of light by nematic vortices and analogy to cosmic rings. Nature Materials, 1 December 2022, https://doi.org/10.1038/s41563-022-01414-y
In this paper, authors use topological spatial patterns of liquid crystal’s optical axis, with single vortex lines to steer beams of light. This reconfiguration of light–matter interaction is manipulated using electric field and light as external stimuli. With the help of photopatterning, periodic arrays of vortices are fabricated to allow fission of nematicons, which results in very interesting lightening-like propagation patterns. The study shows that high-birefringence liquid crystals that contain spatial trajectories of vortex lines and predesigned patterns can steer light beams to form closed loops or knots. Apart from having numerous technological applications such as inbeam steering, telecommunications, anticounterfeiting, etc., these resulting vortex lattices can also act as an excellent model system to study light interaction with defects, such as the light-steering action of cosmic rings.
H. Chi, A. Gavrikov, L. Berlyand, I.S. Aranson, Interaction of microswimmers in viscoelastic liquid crystals. Communications Physics, 5, (2022), 274.
Active matter such as bacteria in liquid crystals is widely studied. Where there is ample research on these microswimmers’ motility in viscoelastic liquid crystals, there is still a gap in our understanding of their motion in anisotropic fluids. In this paper, the authors study the interaction of bacteria in a mucous-like environment simulated by viscoelastic liquid crystals. They observed numerous fascinating phenomena regarding bacteria movement. For instance, they showed that after direction reversal, individual swimmers move faster along the same track. This is because of the medium’s memory that forms a transient tunnel. Furthermore, for two swimmers travelling along the same track, the one behind has a higher velocity and eventually catches up with the first one. Microswimmers travelling parallel to each other attract, and then continue their journey in close proximity. Those launched at different angles form a train, where, after a while, the one behind follows the path of the one in front of it.