Light-induced layer by layer thickening in photosensitive liquid crystal membranes

Photosensitive smectic membranes of pure liquid crystal (LC) were studied under white light illumination. A thickness increase is observed in the illuminated film area. Appropriate light and thermal conditions lead to a thickening layer by layer process. This unusual phenomenon is opposite to the well-known step-by-step thinning transitions under heating. We give a phenomenological interpretation for thickening based on layer transport of LC matter towards the illuminated area.