| Author: | Tsoi, Chi Chung |
| Title: | Microfluidic droplet arrays for high-throughput screening of microalgae |
| Advisors: | Zhang, Xuming (AP) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Microalgae Microalgae -- Biotechnology -- Economic aspects Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Physics |
| Pages: | xix, 123 pages : color illustrations |
| Language: | English |
| Abstract: | Microalgae are rich in special nutrients such as lipids, polysaccharides, and unsaturated fatty acids (DHA, EPA). They hold great promise as new resources for health foods, nutraceuticals and biofuels. The selection of highly-productive species is crucial to the commercial success (ingredients, productivity, cost) of microalgae. The prevailing methods often use large bioreactors to grow microalgae and have the drawbacks of intensive labour work, long time (typically 6 months) and low success rate. On the other hands, microfluidics has seen great success in drug screening using mammalian cells. Similarly, microfluidics may be a powerful solution to screening microalgal cells. This PhD research aims to develop novel microfluidic techniques for high- throughput screening of gene-mutated microalgal species, particularly in two parts: (1) a novel design to form a large array of single microalgal cells that allows to electrically manipulate any individual cell (called addressable XY array); and (2) a new method to form large number of droplets that contain microalgal cells (called EWOD templated pressing method). Both are original ideas and enabling techniques for microalgal screening, with high scientific novelty and strong application prospects. In one part of this study, a unique design called electrically-addressable microfluidic XY array (in short, XY array) is developed to form a large array (16x16) of microalgal cells for high-throughput screening. The XY array arranges N parallel electrode lines (called X lines) on the top and another N lines (called Y lines) on the bottom to form an NxN array of microalgae and to use AC electric signals and thus dielectrophoretic force to control the trap and release of any individual microalgal cell at any specific unit of the XY array. Particularly, this XY array needs only 2N electrode lines to manipulate N2 cell units and is thus more suitable for large array and high throughput (e.g., 1,000 x 1,000). In the other part of this research, an original EWOD templated pressing method is developed to form a large number of pL droplets (e.g., 105) in batch using photo-patterned SU-8 microwells fabricated on an ITO glass slide as the template. Compared to previous literature, which achieved production rates of less than 10%, this chip demonstrates an impressive production rate of over 95% in generating more than 106 droplets of 0.9 pico-litres in one batch. In addition, this method could be used to generate smaller droplets with the volume of femto-litres or even atto-litres. In summary, this PhD study has developed two enabling techniques to select the best few highly-productive species from a large number of gene-mutated microalgal cells in a more controllable and automatic manner. They would cut short the screening time from about 6 months using the current manual methods to about 2 weeks, and would drastically increase the success rate (the best 10 from 104 cells). This work would promote the research and development and microalgae and expand to other applications that use an array of microparticles, such as drug screening, stem cell differentiations and bacterial studies. |
| Rights: | All rights reserved |
| Access: | open access |
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