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09/06/10 - MICROFLUIDICS EVOLUTION – THE NEW MICRO LAB

Labotec recently installed an Elga water purification system in the first micromanufacturing laboratory established in South Africa to focus on microscale components. Materials Science and Manufacturing at the CSIR has taken the lead in developing a new technology; microfluidics, which deals with the behaviour, control and manipulation of fluids in nano and picolitre ranges. Applications here could be far reaching and stretches across areas such as disease detection, micro fuel cells, chemical and pharmaceutical production. For instance, the implications of point-of-care medical diagnostics delivered on a micro-scale chip the size of a coin to remote areas and clinics throughout the country may become a reality.

The goal of microfluidics is to automate standard lab processes and conduct chemical and biochemical processes in a miniaturised format on a chip. Small quantities of reagent, less waste generation, faster reaction times and cost-efficiency are some obvious advantages, while the micron-sized particles can be manipulated with great precision for specific purposes. Early detection of viral load of HIV/AIDS is one such physical application, or a water sensor to detect e coli / cholera in rivers and dams another future proposed project for the researchers at the centre.

Silicone wafers are used as a substrate to build moulds for the microfluidic channels. A photoresist, SU-8, is spun onto the wafer, exposed to UV light, developed and baked to yield the required channel structure. The Elga Purelab water purification system delivers deionised water to rinse the manufactured “wafers” in the new cleanroom laboratory at the CSIR. These “wafer moulds” form an integral part of micromanufacturing. Once the “wafer” is developed, washed with a high pressure spray and boost pump that accompanied the Elga purification system, they are baked on a hotplate to evaporate any moisture. It was important that the whole purification unit fitted neatly and cleanly into the dust-free area allowing easy access while working in a laminar flow. The high pressure spray nozzle is attached to the side of the fume hood, and since the system is a fully recirculating Type II system, water on-demand is always of the required specification quality. Running costs are minimised on the system, and the wrap around reservoir helps to save space.

A microfluidic channel is a structure fabricated in silicon, glass or polymer on a plate. Three dimensional channels typically 25 – 100 microns in size are used for transporting the liquid; blood, enzymes, gas, surfactants, lipase etc. The “laboratory on-a-chip” is created by combining channels, mixers, reservoirs, diffusion chambers, valves and more onto a single chip. The particles can be stained to differentiate between the sizes to facilitate quantitative analysis of the performance of the circuit. Once leakages and design particulars are ironed out, testing and optimisation is possible.
Already with a couple of months of research and “wafer” manufacturing behind them, the team at CSIR are optimistic about the potential impact of microfluidics on a resource-poor country like South Africa.
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