Simulations to develop integrated fluid environment

Well-developed integrated fluid environments can help biochemical analysis to advance. The fluid environment can be divided into the fluid body and the solid substrate that supports the fluid. This project has helped to progress various aspects that make up effective integrated fluid environments through the use of computer simulations. The first category of efforts made related to investigations on the fluid body. It is difficult to measure the local temperature in a liquid volume. A scheme has been developed in this work to accurately measure liquid temperature within a short period of time by modelling a nanorod’s Brownian motions detected by a plasmonic optical resonator. On the other hand, Brownian motion can be disruptive during cell interrogation but direct physical manipulation can cause damage to them. A scheme to control particle harness the push-pulling ability of an optical tweezers has been shown experimentally and backed by modelling results. The scheme operates in a way such that any particle after processing can be replaced selectively with another particle seamlessly. Optical tweezers, however, cannot control smaller molecules. Solutes containing samples of interest (e.g. DNA) are often available at low concentration and can be difficult to detect. Simulation conducted showed that the concentration can be increased by applying an electric potential across a channel with step openings. More specifically, the simulations showed that junctions with sharp corners opening performed better than that with tapered corners in terms of concentration enhancement. Besides molecules, bacteria often exist in fluid environment and its movement can be affected by the fluid oxygen concentration via an aerotaxis effect. In order to control the oxygen concentration, a new approach to control bubble movement has been shown experimentally, and numerical modelling has shown that bubbles moving at the speed of Reynolds number = 0.2 can create an oxygen profile that improved the bacteria concentration at a band better. The second category of efforts made related to studies on the fluid-supporting substrate. Microplates are a common tool in biochemical analysis. However, it suffers from the edge effect when incubated. Modelling showed that this v unintended discrepancy is the result of different evaporation rates between the inner and outer wells. It was shown that transparency microplates are more immune to this problem than standard microplates. Transparency microplates, on the other hand, can suffer from spillage problem during impact. Simulations conducted to study the mechanics of droplet’s spillage showed the effect of surface deformation. Instead of using a hydrophobic surface as a substrate, superhydrophobic surfaces are gaining popularity in biochemical analysis due to its lower adhesion losses. A new method to transform PTFE to a superhydrophobic surface by impacting particulate sprays was developed via experiment. Numerical simulations have been conducted allowed better understanding of the process.