ACS Nano http://doi.org/pb3 (2013)

Fluorescent microscopes are rarely thought of as portable devices due to their relatively bulky and expensive components. Smaller devices can impose limitations on the strength of the fluorescent signal and can have increased background noise due to leakage of the excitation light and detection noise.

Aydogan Ozcan and colleagues at the University of California, Los Angeles have now developed a lightweight attachment for a smartphone that can serve as a mobile fluorescent microscope capable of imaging nanoparticles. The device uses a 450-nm laser diode at a high illumination angle, which is instrumental in reducing the background noise. The noise is further suppressed by using a thin-film interference filter. Samples, which can be solid or liquid, are imaged on a small platform inserted into the phone.

The researchers evaluated the performance of the device by imaging fluorescently labelled polystyrene beads and were able to detect individual beads with diameters of around 100 nm. They also showed that the mobile microscope could be used to image single human cytomegaloviruses that were fluorescently labelled. Although these virus particles are larger than the polystyrene beads (with diameters of 150 to 300 nm), they can be difficult to detect because they contain a low density of fluorescent labels.

Aydogan Ozcan and colleagues suggest that the portable device could be used in various field settings, including point-of-care applications.