Recent Advances in Molecular Alignment by Scanning Wave Photopolymerization of Liquid Crystals

The precise control of molecular alignment in liquid crystals is pivotal for the development of next-generation devices in fields such as electronics, photonics, and robotics. Despite advancements in molecular alignment techniques, achieving fine, two-dimensional molecular alignment still requires complex processes. In this review, we highlight scanning wave photopolymerization (SWaP), a technique that induces molecular alignment through molecular flow generated by spatiotemporal photopolymerization. This method enables direct and precise two-dimensional alignment in a single step, solely by controlling the shape and movement of light. Since SWaP utilizes flow fields—a universal phenomenon across all molecules – as its driving force, it allows for controlled alignment that is independent of molecular structure, polymerization system, and substrate surface treatment. Moreover, recent studies have shown that this technique enables (1) significant improvement of polymerization efficiency, (2) the formation of high-aspect-ratio structures such as canals and wells, underscoring its considerable potential. SWaP is expected to emerge as a transformative technology for fabricating high-performance devices with precise molecular alignment and complex surface topographies, while minimizing energy consumption.