The miniature microscopes have a multitude of potential uses. Because they're cheap and compact, Yang hopes that they'll be used in portable devices in the developing world. "The gold standard for detecting malaria is examining a blood sample under a high-power microscope," he says. However, conventional microscopes are too fragile, cumbersome, and power hungry to be implemented in many places where the blood parasite is prevalent. Ten-dollar microscopes could be inserted into PDA-size devices that display the images on a small screen. Such a device would probably cost about $100; the microscope systems could be replaced like printer cartridges when they show wear and tear.

The devices might also be useful for tracking cancer. Yang recently began a collaboration with Richard Cote, a urologist at the University of Southern California who is developing devices for real-time monitoring of cancer therapies. Cote's technology uses filters to pluck large, wandering cancer cells from the blood. Doctors need to look at the cells to determine whether a patient's cancer is spreading, but putting the cells onto a microscope slide simply isn't practical. "Lenses are the limiting proposition," and Yang's system eliminates them, says Cote. Yang also envisions implantable microscopes that search for wandering cancer cells and identify a subset of images for a clinician to examine manually.

High-throughput imaging will be a boon for pharmaceutical companies, says Peter So, head of the Bioinstrumentation Engineering, Analysis, and Microscopy Lab at MIT. During drug development, hundreds of versions of the same compound are first tested in cells. The current state of the art involves plating cells in tiny wells and then exposing them to drugs, then testing their response using a combination of technologies, including microscopy. Microfluidic systems for handling cells would require smaller samples and would speed the process, but they haven't been widely implemented because until the Caltech advance, there hasn't been a way to integrate imaging into these devices, says So.

Yang says that he is talking with several companies about commercializing the microscope on a chip, and he hopes that it will be on the market in five years. He's also working on modifications to the system to enable fluorescence imaging--the microscopes currently can't detect colors--and to increase the scopes' resolution.