Feature Article The Colloidal Metamorphosis Time Division Multiplexing of the Reflectance State

Typical display screens are rigid and static, and they display the entire content in the same diffused manner. Furthermore, a screen’s material can’t be changed dynamically. However, in the real world, objects consist of dif-ferent materials, with most materials having a distinguishing reflectance. It would be useful if a screen could reproduce a material’s reflectance. We aim to achieve this by changing the screen’s optical state. When digital content is shown on a static surface, a significant amount of information is lost, including information regarding color, shape, depth, texture, and material. An object’s appearance is determined mainly by its con-stituent materials ’ reflectance. If we could control this reflectance on the screen, we would no lon-ger need to simulate certain ma-terials by adjusting the bright-ness. In a previous study, we used ultrasonic phased arrays to control the reflectance of a colloidal display made of soap film.1 We’ve extended that research by determining how to reproduce a material’s reflectance and evaluating the reproduced appearances. By alternating the soap film’s reflectance at high speed through time division multiplexing, we can simulate different materials ’ reflectance, making the display more realistic. Figure 1 diagrams our system. Theories Here we describe the theory behind our colloidal display. Capillary Waves on Soap Film Diffusion on the ultrasound-activated colloidal film is caused by the capillary waves, which are dominated by surface tension. The dispersion rela-tion of the waves on the display is λ pi