Local researchers are combining microfluidics and optics to create new devices for research.
Yvonne Carts-Powell
The idea of doing biochemical analyses on a chip is not entirely new with the advent of tools such as microarrays for studying gene expression. But researchers in the field of microfluidics say a lot more laboratory experiments can be miniaturized and put onto a chip. With channels no wider than tens to hundreds of micrometers, such a “lab–on–a chip” could enable the analysis of molecules and cells using nanoliter volumes of liquids, thus reducing the cost and time of the experiment.
While the technology hasn’t been widely adopted yet by laboratory scientists, microfluidics researchers are keen on further enhancing their chips by adding light-based technologies to them.
“With optofluidics you have the potential to put not just the beakers, pumps, and separation stages on a chip, but also the microscope, spectrometer, or plate reader,” says Stanford optofluidics researcher Adam Cohen.
Researchers in the lab of George Whitesides in Harvard’s chemistry and chemical biology department are working on building light sources into microfluidic chips. One of the ultimate goals of microfluidics research is to integrate entire analytical instruments onto chips. For instruments that use light, this means the chip would need a light emitter and a detector on board.
Sindy Tang, a graduate student in the Whitesides lab, is adapting a light source that once was a staple in benchtop spectroscopy: fluorescent liquid dyes that emit laser light of varying wavelengths. Laser diodes or lamps located on or off the chip excite the tiny volumes of dye into producing a laser beam on the chip. The Whitesides group routed three dyes through one channel at the same time, producing three different colors of laser light at once.
It may be possible, Tang says, to integrate such “dye lasers” into an inexpensive 96-well bio-assay chip developed by Whitesides and his team several years ago. This would provide an almost complete microanalytical system in a single device.
Another local group is taking a different approach to putting a light source on a microfluidic chip. Researchers in Federico Capasso’s lab at Harvard want to integrate the recently invented quantum cascade laser into microfluidic chips. This light source can provide a wide range of wavelengths in the infrared range.
A number of companies have commercialized microfluidic devices for researchers. But building optical components into them will require more development before they become common tools. Researchers are still working to develop methods for building cheap and reliable chips that combine the plumbing needed for liquids, the components for the electronics, and the optical paths for light.
To Cohen, the future of the technology is promising. “Because of the small size and highly parallel architecture [of microfluidic and optofluidic chips], you can also create new tools that don’t have any tabletop equivalents.”