Engineers detect and measure individual DNA molecules using smartphone microscope

Fluorescence microscopes use technology that enables them to accomplish tasks not easy to achieve with normal light microscopes, including imaging DNA molecules to detect and diagnose cancer, nervous system disorders such as Alzheimer's disease, and drug resistance in infectious diseases.

These microscopes work by labeling the samples with fluorescent molecules that are "excited" with a laser. This process gives off different colored light that the microscope detects and uses to build images of fluorescently labeled samples, visualizing objects that are 100 to 1000 times smaller than the diameter of human hair.

These fluorescent microscopes are expensive, bulky and relatively complicated, typically making them available only in high-tech laboratories.

Now researchers from UCLA's California NanoSystems Institute have reported the first demonstration of imaging and measuring the size of individual DNA molecules using a lightweight and compact device that converts an ordinary smartphone into an advanced fluorescence microscope.

The mobile microscopy unit is an inexpensive, 3-D-printed optical device that uses the phone's camera to visualize and measure the length of single-molecule DNA strands. The device includes an attachment that creates a high-contrast, dark-field imaging set-up using an inexpensive external lens, thin-film interference filters, a miniature dovetail stage and a laser diode that excites the fluorescently labeled DNA molecules.