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Electroactive polymer enables more compact lab-on-a-chip

Posted: 15 Jul 2013 ?? ?Print Version ?Bookmark and Share

Keywords:RIKEN Quantitative Biology Center? lab-on-a-chip? biological test? pneumatic valve? electroactive polymer?

A team of researchers at RIKEN Quantitative Biology Centre has produced a new type of microfluidic control valve that takes up significantly less space on a microchip than existing approaches to create more compact and more economical lab-on-a-chip devices. By constructing parallel arrays of microfluidic pathways, they are working to produce 'lab-on-a-chip' technologies that allow multiple biological tests to be performed using just a drop of blood or urine.

In the majority of today's microfluidic devices, silicone pneumatic valves are used to manipulate liquid samples. Pneumatic valves, however, require noisy compressors and complicated air channel systems, which are often too bulky for practical lab-on-a-chip applications. Piezoelectric actuatorsinorganic crystals that change shape when electrically stimulatedare feasible alternatives, but while piezoelectric materials are less obtrusive than pressurized air technology, they are excessively large when compared to the size of the microchip itself.

A novel electroactive polymer stop valve for lab-on-a–chip technology

Figure 1: A novel electroactive polymer stop valve for lab-on-a–chip technology.

Yo Tanaka and his colleagues instead investigated the remarkable properties of electroactive polymers. These materials are rubber-like organic compounds that expand and contract when exposed to an electric current. As electroactive polymers can exhibit large mechanical strain force at small scales, the team deduced that creating membranes incorporating these materials could be a promising way to miniaturise microfluidic control valves.

After experimenting with many valve shapes, the researchers settled on a micrometre-sized, dome-shaped polymer diaphragm sandwiched between soft electrode sheets. They tested its ability to stop flow by fabricating it on top of a small hole drilled into a microfluidic channel. By monitoring fluorescent polystyrene tracking beads using high-speed video cameras, the team saw that stimulating the electroactive polymer caused the diaphragm to expand and close off the microchannel at sub-second speeds, nearly identical to the response time of piezoelectric actuators but with an order-of-magnitude smaller form factor. Furthermore, the polymer structure strongly resisted leaks because of its resilient structure.

The researchers note that the improved size-scaling of their valve system should prove more efficient for the sorting of biological cells than current fluorescent technology. Othermore mobileapplications also may be on the horizon. "Many portable devices for personal diagnosis, environmental analysis, or fuel cells could benefit from these miniaturized valves," noted Tanaka.

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