'Liquid pistons' promise better camera lenses, eye implants, drug delivery

Researchers at Rensselaer Polytechnic Institute have developed "liquid pistons" that offer extremely precise displacement of fluid, a boon for mobile phone cameras, implantable eye lenses, medical imaging equipment and drug delivery devices.

The engineers developed the technique, in which oscillating droplets of ferrofluid -- a liquid saturated with metal nanoparticles -- displace a surrounding liquid.

The technique allows for researchers to shift, or "pump," tiny volumes of liquid with precision, without causing the wear-and-tear found in systems that use solid moving parts.

The applications for the technique are many:

• Adaptive liquid lenses.
• Micro-displacement pumps for labs-on-a-chip.
• Liquid switches.
• Implants that deliver tiny, timed doses of drugs.

Led by professor Amir Hirsa, the research team developed a liquid piston comprised of two ferrofluid droplets situated on a substrate approximately the size of a piece of chewing gum.

The substrate had two holes in it, one droplet in each hole. The entire device was placed in a chamber filled with water.

The presence of an electromagnet caused one of the ferrofluid droplets -- "the driver" -- to vibrate, which in turn prompted a series of forces that cause the second droplet to vibrate in an inverted pattern. Together, the droplets became a working piston, which could be adjusted by the researchers by modifying the magnetic fields applied to it.

In water, the droplets also functioned as a pump, displacing fluid in the chamber as a droplet moves.

By passing light through the droplets, they also serve as a miniature camera lens, for which the focus automatically changes as the droplets move back and forth. The images can be captured electronically and unfocused frames can be edited out using software, leaving crisp video at 30 hertz, the quality of a conventional computer webcam, but using far less energy.

Their research was supported by the Defense Advanced Research Projects Agency, or DARPA. It was published in the February 2011 issue of the journal Lab on a Chip.

This post was originally published on Smartplanet.com