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 microscopic particles.

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 Caltech.

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.