Press Release

Breakthrough in Photonic Biosensors Could Lead to Fast, Super-Accurate Diagnostics and Detection

Steven Arnold

Researcher Stephen Arnold observes a whispering gallery mode biosensor setup comprising a microchannel containing a fiber-optic filament, a silica microsphere, and a laser and detector within a small device.


The discovery follows years of groundbreaking work by Arnold, who in 1995 discovered that an optical fiber could excite what he termed Whispering Gallery Mode (WGM) in polymer micro-beads less than one-third the diameter of a human hair. Further discoveries and patents led to WGM biosensors capable of gauging the mass of viruses, proteins, and other nanoparticles by sending them into spacecraft-like orbit around the micro-bead, thanks to a photonic “tractor beam” caused by the resonating light (watch video). Arnold and collaborators then devised a way to make these WGM biosensors sensitive enough to identify even the smallest individual bio-particles from the RNA virus MS2 to single molecules down to 6 zepto-grams (6x10-21 grams), below the mass of all known cancer markers. Many companies, including Genalyte, employ WGM biosensors in diagnostic products that can perform dozens of bioassays in minutes.


Arnold, who also is a member of the Othmer-Jacobs Department of Chemical and Biomolecular Engineering at NYU, and his fellow researchers, including Jehovani Lopez, Eshan Treasurer, Kaitlynn Snyder, and David Keng, recently published their findings in Applied Physics Letters.



“Charge controls the ability to transport particles that are interacting with cells and other objects that possess electric fields,” he said. “By determining the charge of a virus, for example, you can understand how it can be transported to the cell surface. You need to understand this mechanism in order to engineer a WGM micro-bead that has a specific antigen at a specific region of its surface so that the biosensor can attract specific pathogens or other biomolecules.”


“The difference in the strength of the force being measured is extraordinarily small,” said Arnold, who explained that the measured electrostatic force involved in keeping a nanoparticle in orbit was only 0.00000000000003 (3x10-14) pounds. “With this force in hand both the charge on the nanoparticle and the microcavity charge density could be calculated through a series of experiments.”

The team next plans to use the discovery to develop technology for “photonic printing,” the ability to quickly create numerous task-specific WGM biosensors, with specific molecules attached to specific areas of the micro-bead.


“Whispering Gallery Mode Coulometry of the Nanoparticle-Microcavity Interaction in Aqueous Solution” is available at

Note: Images available at 

About the New York University Tandon School of Engineering