GEN-ERIC News

Microscopic particles can be steered through the tiny channels of a microfluidic chip using light, US researchers have shown. They modified standard piece of lab equipment to direct particle traffic using light, and say the trick could prove vital for rapid chemical and biological analysis with handheld devices. Microfluidic chips contain microscopic tubes that can be used to ferry cells and particles around for chemical or biological experimentation. Controlling fluids and particles at small scales is difficult, however. The US team, led by David Erickson and Michal Lipson at Cornell University, Ithaca, US used light to control these unruly particles. They constructed a microfluidic chip with “waveguides” built into the walls of each fluid channel. The waveguides were designed to act like leaky pipes: as laser light passes through, it does not bounce perfectly off the inside walls, and a weak electromagnetic field – called the evanescent field – leaks out. Mystery ‘cushion’Particles that flow across a waveguide’s path are captured by its electromagnetic field and pulled along in the same direction as the light inside the waveguide. The approach can even steer particles around a bend.