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Researcher adds glass microfluidics into lab-on-a-chip

Posted: 08 Jul 2013 ?? ?Print Version ?Bookmark and Share

Keywords:lab-on-a-chip? glass? polydimethylsiloxane? microfluidic?

Most lab-on-a-chip devices are formed from polydimethylsiloxane (PDMS), an inexpensive plastic that is easy to pattern with microfluidic elements. Valves, in particular, take advantage of the plastic's elasticitysimply applying or releasing pressure can close or open a channel in the device, controlling fluid flow. The use of plastic, however, has some disadvantages that could be remedied by using glass. Unfortunately, glass chips have proved difficult to fabricate due to their fragility. Yo Tanaka from the RIKEN Quantitative Biology Centre has developed a reliable and durable system for incorporating glass microfluidics into lab-on-a-chip devices.

Plastics have several disadvantages, including degradation when exposed to reactive chemicals and a tendency to adsorb sample molecules before they can be analysed. They can also interfere with analysis techniques that rely on shining a light through the device due to their imperfect transparency. Glass is an attractive alternative because it is chemically resistant, transparent and can withstand higher fluid pressures than PDMS. Producing flexible and durable glass valves, however, has proved difficult.

To allow glass to be used in these devices, Tanaka developed a Teflon frame to hold an ultrathin sheet of glass so that it could be handled without breaking and incorporated the frame into an all-glass lab-on-a-chip.

An all-glass lab-on-a-chip

Figure 1: An all-glass lab-on-a-chip. Source: The Royal Society of Chemistry.

Next, Tanaka used hydrogen fluoride to etch channels and chambers into a pair of glass slides, and covered these chambers with ultrathin glass sheets in a way that allowed fluid to be prevented from passing through the chamber by simply pressing down on the glass cover. He then fused the glass sheets together by heating them at 750C.

After trying various thicknesses of ultrathin glass sheets, Tanaka found that a 10?m-thick glass film was ideal: strong enough to withstand more than 100 depressions yet able to deform by up to 126?menough to completely close the valve. Tests using water containing small fluorescent polystyrene beads demonstrated that closing the valve using this method blocked fluid flow within 0.12s.

Tanaka now plans to develop his all-glass device for applications such as highly sensitive biochemical analyses and cell studies.

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