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“Liquid Pistons” Could Drive New Advances in Camera Lenses and Drug Delivery
Versatile Liquid Pistons Developed at Rensselaer
Polytechnic Institute Have No Solid Moving Parts, Essentially
Eliminating Wear
Researchers at Rensselaer Polytechnic
Institute 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.
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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 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.
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. The paper will be featured on the cover of the
journal’s February 2011 issue, and can be read online at: http://xlink.rsc.org/?DOI=c0lc00397b
Hirsa’s team developed a liquid piston that is comprised of
two ferrofluid droplets situated on a substrate about the size
of a piece of chewing gum. The substrate has two holes in it,
each hosting one of the droplets. The entire device is situated
in a chamber filled with water.
Pulses from an electromagnet provoke one of the ferrofluid
droplets, the driver, to vibrate back and forth. This
vibration, in turn, prompts a combination of magnetic,
capillary, and inertial forces that cause the second droplet to
vibrate in an inverted pattern. The two droplets create a
piston, resonating back and forth with great speed and a
spring-like force. Researchers can finely control the strength
and speed of these vibrations by exposing the driver ferrofluid
to different magnetic fields.
In this way, the droplets become a liquid resonator, capable
of moving the surrounding liquid back and forth from one
chamber to another. Similarly, the liquid piston can also
function as a pump. The shift in volume, as a droplet moves,
can displace from the chamber an equal volume of the
surrounding liquid. Hirsa said he can envision the liquid
piston integrated into an implantable device that very
accurately releases tiny, timed doses of drugs into the body of
a patient.
As the droplets vibrate, their shape is always changing. By
passing light through these droplets, the device is transformed
into a miniature camera lens. As the droplets move back and
forth, the lens automatically changes its focal length,
eliminating the usual chore of manually focusing a camera on a
specific object. The images are captured electronically, so
software can be used to edit out any unfocused frames, leaving
the user with a stream of clear, focused video.
The speed and quality of video captured from these liquid
lenses has surpassed 30 hertz, which is about the quality of a
typical computer web cam. Liquid lenses could mean lighter
camera lenses that require only a fraction of the energy
demanded by today’s digital cameras. Along with handheld and
other electronic devices, and homeland security applications,
Hirsa said this technology could even hold the key to
replacement eye lenses that can be fine-tuned using only
high-powered magnets.
“There’s really a lot we can do with these liquid pistons.
It’s an exciting new technology with great potential, and we’re
looking forward to moving the project even further along,” he
said.
Along with Hirsa, co-authors on the paper are Rensselaer
doctoral graduates Bernard Malouin Jr., now with MIT’s Lincoln
Laboratory; and Michael Vogel, a private research consultant;
Rensselaer mechanical engineering doctoral student Joseph
Olles; and former postdoctoral researcher Lili Cheng, now with
General Electric Global Research.
This study was supported with funding from the Defense
Advanced Research Projects Agency (DARPA).
For more information on Hirsa’s research at
Rensselaer, visit:
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Published
January 10,
2011 |
Contact: Michael Mullaney
Phone: (518) 276-6161
E-mail: mullam@rpi.edu |
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