‘Liquid Pistons’ May Advance Camera Lenses

A few unassuming drops of liquid locked in a very precise game of "follow the leader" could one day be found in mobile phone cameras, medical imaging equipment, implantable drug delivery devices, and even implantable eye lenses.

Engineering researchers at Rensselaer Polytechnic Institute (RPI) have developed liquid pistons, in which oscillating droplets of ferrofluid precisely displace a surrounding liquid. The pulsating motion of the ferrofluid droplets, which are saturated with metal nanoparticles, can be used to pump small volumes of liquid. The study also demonstrated how droplets can function as liquid lenses that constantly move, bringing objects into and out of focus.

Researchers at RPI have developed liquid pistons, which can be used to precisely pump small volumes of liquid. Comprising the pistons are droplets of nanoparticle-infused ferrofluids, which can also function as liquid lenses that vibrate at high speeds and move in and out of focus as they change shape. These liquid pistons could enable a new generation of mobile phone cameras, medical imaging equipment, implantable drug delivery devices, and possibly even implantable eye lenses. (Image: Rensselaer/Hirsa)

These liquid pistons are highly tunable, scalable, and — because they lack any solid moving parts — suffer no wear and tear. The research team, led by Rensselaer Professor Amir H. Hirsa, is confident this new discovery can be exploited to create a host of new devices ranging from micro displacement pumps and liquid switches, to adaptive lenses and advanced drug delivery systems.

"It is possible to make mechanical pumps that are small enough for use in lab-on-a-chip applications, but it's a very complex, expensive proposition," said Hirsa, a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer. "Our electromagnetic liquid pistons present a new strategy for tackling the challenge of microscale liquid pumping. Additionally, we have shown how these pistons are well-suited for chip-level, fast-acting adaptive liquid lenses."

Results of the study are detailed in the paper "Electromagnetic liquid pistons for capillarity-based pumping," recently published online by the journal Lab on a Chip.

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