The new microscope, which is planned to be used
for field "systems on a chip" to test blood samples for malaria
or check water supplies for giardia and other pathogens, was developed by
engineers at California Institute of Technology (Caltech). They predict
the finished product will cost approximately $10 a unit, making it very
affordable in the world of custom electronics.
The tiny microscope seems straight out of science fiction, but uses an exotic
technology known as optofluidics to work. By combining computer control
and microfluidics the device uses fluid channels to control sample flows.
The main "lens" is a sensor the size of Washington's nose on a
quarter. Changhuei Yang, assistant professor of electrical engineering
and bioengineering at Caltech, helped lead the efforts.
He states, "Our research is motivated by the fact that microscopes have
been around since the 16th century, and yet their basic design has undergone
very little change and has proven prohibitively expensive to miniaturize. Our
new design operates on a different principle and allows us to do away with
lenses and bulky optical elements. The whole thing is truly compact--it
could be put in a cell phone--and it can use just sunlight for illumination,
which makes it very appealing for Third-World applications."
Part of the device's charm is its easy assembly leading to low costs. The
production starts by coating a metal grid onto a charge-coupled device (CCD)
sensor, the same type of sensor that takes a digital camera's picture.
Then tiny, five micrometer-spaced holes are punched in the metal. From
there microfluidic channels are formed atop the sensor grid. The chip is
illuminated from overhead, only normal sunlight is need.
When the sample flows into the channel bacteria, other particles block out
sunlight creating regions of shadow in the pits similar to a pinhole camera.
The pits overlap slightly resulting in a surprisingly high resolution image of
Professor Yang is currently marketing the chip. He foresees the creation
of portable self-test units that could see use in military deployments.
Also a more complex system, with hundreds of microfluidic microscopes on a
single chip could test for numerous specific pathogens. Xiquan Cui, the
lead graduate student on the project, adds, "We could build hundreds or
thousands of optofluidic microscopes onto a single chip, which would allow many
organisms to be imaged and analyzed at once."
The chips could even see implantation
in the human body for remote monitoring of disease. Says Professor
Yang, "An implantable microscope analysis system can autonomously screen
for and isolate rogue cancer cells in blood circulation, thus, providing important
diagnostic information and helping arrest the spread of cancer."
The research is featured in this month's edition of the journal Proceedings
of the National Academy of Sciences (PNAS) and can be found here.
Other coauthors of the paper were Lap Man Lee; postdoctoral research associates
Xin Heng and Weiwei Zhong; Paul W. Sternberg, the Thomas Hunt Morgan Professor
of Biology and an Investigator with the Howard Hughes Medical Institute; and
Demetri Psaltis, the Thomas G. Myers Professor of Electrical Engineering at
The research received funding from DARPA's Center for Optofluidic Integration
at Caltech, the Wallace Coulter Foundation, the National Science Foundation,
and the National Institutes of Health.
quote: The chips could even see implantation in the human body for remote monitoring of disease. Says Professor Yang, "An implantable microscope analysis system can autonomously screen for and isolate rogue cancer cells in blood circulation, thus, providing important diagnostic information and helping arrest the spread of cancer."