Liquid crystals are a family of materials that can flow like a liquid, while having orientation order, like a crystal. Traditional liquid crystals are formed by small rod- or disk-shaped organic molecules that spontaneously align with each other. The orientation direction of the liquid crystals molecules, or the director, is sensitive to external fields. For example, a few volt of electric field can cause the director rotate 90 degrees and completely change the optical property of the sample. The susceptibility to external fields made liquid crystals an ideal material for optical switching applications, the best example of which is the liquid crystal display (LCD). In this workshop, we will first explain some basic concepts of polarizing optics and test some daily birefringent materials. We will then look into how liquid crystals work as a central component in LCD. We will further characterize the opto-electronic performance of a one-pixel LCD using simple electronics and image analysis software ImageJ. At the end, I will introduce a new direction of liquid crystal research on water-based liquid crystals. By mixing microorganisms into them, we demonstrate a collection of new out-of-equilibrium phenomena that were not seen before in traditional liquid crystals. With this new “living liquid crystals”, we show application potential of “domesticating” microorganisms such as bacteria and parasites, and many more.
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