Pump Up the Volume

by Michael Mullaney on January 26, 2011

Popular Science wrote a nice story recently about the research of Professor Amir Hirsa, whose investigations into tiny liquid-based camera lenses is moving into even more exciting territory.

Here’s what PopSci said:

A pair of magnetic liquid drops oscillating in opposite directions can function as a liquid piston, and could one day be used to deliver drugs, power mobile phone cameras or even serve as implantable eye lenses, according to a new study.

Researchers at Rensselaer Polytechnic Institute embedded drops of ferrofluid, a liquid infused with magnetic nanoparticles, into a thin substrate that was submerged in water. Then they exposed the device to a magnetic field to make one of the droplets vibrate back and forth (up or down in the image above), which caused its partner to oscillate in a mirror pattern. This ballet displaces teeny amounts of liquid, moving it from one chamber to another, according to Amir H. Hirsa, a mechanical engineering professor at Rensselaer. The piston is superfast, allowing micro-scale devices with cycling speeds in the kilohertz range.

The video above shows one of these liquid pistons in action.

Another piece, by EE Times, expands a bit on how the liquid pistons function as a camera:

By carefully oscillating a ferro-fluidic droplet with a magnetic field, the fluids inside can be pumped up-and-down like a piston, allowing the focal length of a lens to be adjusted using even less energy than a micro-electro-mechanical system (MEMS). Because the fields are generated use alternating currents, the lens is constantly cycling between its closest and furthest focal lengths, but the researchers say that software algorithms can easily eliminate any out-of-focus frames. In its demonstrations, the researchers were able to capture in-focus 30 frame-per-second videos as a proof of concept.

What’s great about using a piston made from liquids is that it has no moving parts and therefore will never suffer wear and tear. Moving forward, look for innovations out of Hirsa’s lab employing this new liquid piston technology to create even better cameras, medical imaging equipment, implantable drug delivery devices, and even implantable eye lenses.

See these stories of mine on Hirsa, Controlling Light With Sound: New Liquid Camera Lens as Simple as Water and Vibration, and “Liquid Pistons” Could Drive New Advances in Camera Lenses and Drug Delivery. Also, be sure to check out this Approach post with a wonderful research image of his, which was featured in the popular 2010 Rensselaer Research Calender.