The future of biomedicine lies in the first lensless on-chip microscopic design, which abandons the expensive lenses and large conventional microscopes, instead utilizing microfluidic flow to deliver specimens across arrays of micrometer-size apertures defined on a metal-coated CMOS sensor, generating a direct image projection.

Scientists at the California Institute of Technology anticipate that optofluidic microscopy could address a wide range of biomedical and bioscience needs, as well as reveal new microscope applications. The study appears in the Proceedings of the National Academy Sciences USA.

Conventional microscopes have proved to be an invaluable tool for microorganism studies, cell biology and other fields, but scientists have had a hard time trying to miniaturize it. The basic design of the microscope has remained practically unchanged for the last 400 years, and so did its basic components: objective, lens.

The high costs of such lens however have determined scientists to look for a new method of directly projecting images based on low-cost, viable alternatives to the conventional microscope system. Based on the technology used in regular digital cameras, scientists were able to reproduce high resolution images with the help of mini-microscopes that could cost as much as $10 a piece.

The gravity-driven-flow-based optofluidic microscope system is based on a system of micrometer-size apertures defined on a metal coated sensor. As the metal layer blocks light, light can only be transmitted through the apertures, as a flowing specimen passes through the channel. The image is then reconstructed based on the variations of light intensity across the apertures, while the resolution is limited by the aperture size, scientists noted.

The researchers presented two systems that put aside the conventional microscope design, utilizing microfluidic flow instead. The first system uses a gravity-driven microfluidic flow for sample scanning and is suited for elongated objects, while the second system employs an electrokinetic drive for flow control and is suited for imaging cells and other spherical/ellipsoidal objects.

The on-chip mini-microscopes will not only be useful in terms of size, but also as an automatic on-chip microscopy method, which could be used in multiple applications, such as blood fraction analysis, urine screening for infection, stem cell screening and sorting, tumor cell counting and drug screening, the authors of the study explained.

The compact, simple, and lensless OFM (optofluidic microscopy) can significantly benefit a broad spectrum of biomedicine applications and biosciences researches, scientists pointed out in the study. For example, the availability of tens of even hundreds of microscopes on a chip can allow automated and massively parallel imaging of large populations of cells or microorganisms, making it much more practical than any standard microscope.

Furthermore, the system could provide low cross-contamination risk, as the incredibly low cost makes is completely disposable. The study concluded that in Third World countries, low-cost, compact microscope systems could help health workers that need to travel from village to village to easily identify malaria.

Optical microscopy has become an important part of modern biomedicine and bioscience, and scientists have been dedicating their work to finding new alternative approaches to microscopy, in order to make it more practical and enlarge its array of applications.