Researchers at UC Santa Cruz have developed a new approach for studying single molecules and nanoparticles by combining electrical and optical measurements on an integrated chip-based platform. The device was used to distinguish viruses from similarly-sized nanoparticles with 100 percent fidelity.

Combining electrical and optical measurements on a single chip provides more information than either technique alone. The device incorporates a nanopore that serves two functions: it acts as a "smart gate" to control the delivery of individual molecules or nanoparticles into the channel for optical analysis, and allows electrical measurements as a particle passes through the nanopore.

With the new device, researchers are able to gather electrical measurements on a nanoparticle as it moves through a pore in a solid membrane, and then measure the optical signals when the particle encounters a beam of light in the channel. By correlating the strength of the current decrease as a particle moves through the pore, the intensity of the optical signal, and the time of each measurement, the researchers are able to discriminate among particles with different sizes and optical properties and to determine the flow speed of particles through the channel.

Besides identifying pathogens in a mixture, the researchers can also count the number of virus particles.