Researchers Shine a Light on Compact Medical Sensing with a Self-Illuminating Optical Biosensor

Engineers from the École Polytechnique Fédérale de Lausanne (EPFL), the Barcelona Institute of Science and Technology, ETH Zürich, the Université de Strasbourg, National Yang Ming Chiao Tung University, Yonsei University, and the Institució Catalana de Recerca i Estudis Avançats (ICREA) have joined forces to create the first self-illuminating optical biosensor — capable of operating without the need for an external light source.

"Our work delivers a fully integrated sensor that combines light generation and detection on a single chip," explains co-author Ivan Sinev, a researcher in EPFL's Bionanophotonic Systems Lab. "With potential applications ranging from point-of-care diagnostics to detecting environmental contaminants, this technology represents a new frontier in high-performance sensing systems."

Optical biosensors detect target molecules by using waves of light as a probe, focused down to the nanometer scale through the use of nanophotonic structures at their surface. What they don't do, however, is generate their own light — so while the sensor itself can be tiny, the sensing system becomes bulky and expensive once the light source has been added. The solution: a sensor capable of generating its own light.

"If you think of an electron as a wave, rather than a particle, that wave has a certain low probability of 'tunneling' to the other side of an extremely thin insulating barrier while emitting a photon of light," explains co-author Mikhail Msharin of the team's approach to the problem. "What we have done is create a nanostructure that both forms part of this insulating barrier and increases the probability that light emission will take place."

By feeding the sensor a flow of electrons, in the form of an electrical voltage, the team was able to have it self-illuminate at the same time as detecting target molecules. "Tests showed that our self-illuminating biosensor can detect amino acids and polymers at picogram concentrations – that’s one-trillionth of a gram – rivaling the most advanced sensors available today," explains corresponding author Hatice Altug, head of EPFL's Bionanophotonic Systems Laboratory.

Better still, the resulting sensor is considerably more compact than existing systems — to the point that it could be built into a portable handheld device, rather than the desktop systems currently in use.

The team's work has been published under open-access terms in the journal Nature Photonics.