Microfluids has come very far since its origin1 and found applications in a broad range of fields. It would be better if I skip the common applications as readers of the blog might be well aware of these applications and bring your attention towards unexplored and emerging new directions in liquid crystal research. The field of microfluidics has barely crossed lines with liquid crystals – nature’s delicate phase of mater2. Liquid crystals are wonderful materials not only because of their beautiful, vibrant textures or their ubiquitous use in the flat panel display technology but also because of their unique molecular alignment which gives them an orientational order like solid and flow properties of liquids. This is why they are sometimes referred to as the fourth state of matter.
Due to recent advancements in organic materials, OLEDs are slowly replacing liquid crystals as the material of choice in the display industry. A focus of liquid crystals researches is moving to field like flat optics3 and biomimetics4 but it not enough to offset the loss. The liquid crystals industry giants are looking for newer avenues for revenue generation and microfluidics could be the way. From the point of view of microfluidics, one of the areas which have barely received attention, is the field of liquid crystals emulsions. One case of liquid crystal emulsion is polymer dispersed liquid crystal or PDLC which are used in windows, popularly known as smart windows5. Existing methods to create such emulsions results in polydisperse droplets. However, David Wietz et al at Harvard proposed a new co-flow microfluidic technique to create monodisperse double emulsions6. Researchers later used this technique to create monodisperse liquid crystals emulsions.
Fig. 1 shows monodisperse liquid crystal double emulsion droplets from my research work. However, the technique proposed used old-school glass capillary microfluidics. This technique was quickly caught the attention of the liquid crystal fraternity and they soon applied it (without any modification) to create liquid crystal emulsions. As far as my knowledge is considered, it is upsetting to admit that almost all of the research publications have used old-school glass microfluidics to generate these emulsions. This could possibly be attributed to the lack of awareness of about the advanced microfluidic techniques in a seemingly dissimilar field of science. In my case, it was a lack of sufficient funding which prevented me to utilize the advanced techniques to create possible new products and devices.
Lack of awareness about microfluidics amongst other interest groups and its cost of implementation could be major issues holding its expansion beyond its traditional sphere of influence. Take for example this review paper by Malthias et al.7 where it is suggested that the confinement of liquid crystals in unconventional geometries will unravel many possibilities. Yet this is only one instance of unrealized opportunities!
1. Whitesides, G. M. The origins and the future of microfluidics. Nature 442, 368–373 (2006).
2. Collings, P. Liquid Crystals: Nature’s Delicate Phase Of Matter. Liquid Crystals: Nature’s Delicate Phase Of Matter (2002).
3. Tabiryan, N., Roberts, D., Serabyn, E., Steeves, D. & Kimball, B. Superlens in the skies: liquid-crystal-polymer technology for telescopes. SPIE Newsroom (2016). DOI: 10.1117/2.1201601.006317
4. Hirst, L. S. & Charras, G. Biological physics: Liquid crystals in living tissue. Nature544, 164–165 (2014).
5. Fergason, J. L. Encapsulated liquid crystal and method. (1981). DOI: https://patents.google.com/patent/US4605284
6. Utada, A. S. et al.Dripping, Jetting, Drops, and Wetting: The Magic of Microfluidics. 32, (2007).
7. Matthias, H. et al. Liquid crystals in micron-scale droplets, shells and fibers Liquid crystalline polymers: development trends and photocontrollable materials Recent citations. J. Phys. Condens. Matter Top. Rev. • OPEN ACCESS (2017). DOI:10.1088/1361-648X/aa5706
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Sumanyu Chauhan is a graduate researcher in the Chemical Physics Interdisciplinary Program at the Advanced Materials and Liquid Crystal Institute, USA. His current research interests are in liquid crystal emulsions, microfluidic devices, mixed lyotropic systems, and X-ray diffraction.