'Lab-On-Chip' Technologies Combine Electric Fields with Laser

The technologies could bring innovative sensors and analytical devices for "lab-on-a-chip" applications, or miniature instruments that perform measurements normally requiring large laboratory equipment.

The method, called "hybrid optoelectric manipulation in microfluidics," is a potential new tool for applications that include medical diagnostics, testing food and water, crime-scene forensics, and pharmaceutical manufacturing. The technology works by first using a red laser to position a droplet on a platform specially fabricated at Purdue University (West Lafayette, IN, USA).

A highly focused infrared laser is used to heat the droplets, and then electric fields cause the heated liquid to circulate in a "microfluidic vortex." This vortex is used to isolate specific types of particles in the circulating liquid, like a microcentrifuge. Particle concentrations replicate the size, location, and shape of the infrared laser pattern. Systems using the hybrid optoelectric approach can be designed to precisely detect, manipulate, and screen certain types of bacteria, including particular strains that render heavy metals less toxic.

The technology also may be used as a tool for nanomanufacturing because it shows promise for the assembly of suspended particles, called colloids. The ability to construct objects with colloids makes it possible to create structures with particular mechanical and thermal characteristics to manufacture electronic devices and tiny mechanical parts.

Steven T. Wereley, PhD, a Purdue University professor of mechanical engineering, said, "These types of technology are good at being very dynamic, which means you can decide in real time to grab all particles of one size or one type and put them somewhere. We can, say, collect all the particles that are 1 μm in diameter or get rid of anything bigger than 2 μm, so you can dynamically select which particles you want to keep.” The article was published on July 7, 2011, in Lab on a Chip.

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