Nanoscale printing for non-invasive and fast glucose detection
Nanoscale printing for non-invasive and fast glucose detection
"We showed that the versatile printing capability of our S-nTP applicable on diverse surfaces would be able to realize unique SERS platforms that can provide superior convenience and accuracy of measurement"Yeon Sik Jung

A new nanotechnology platform offers the promise of improved glucose sensing from contact lens without the need to draw blood to check on glucose levels. The non-invasive technology can test tears or contact lens using optical sensing based on surface-enhanced Raman spectroscopy (SERS).

The study, which featured in Advanced Materials [Jeong et al. Adv. Mater. (2016) DOI: 10.1002/adma.201602603], was inspired by the Google contact lens, which is being developed to measure glucose levels from tears, before the results are transmitted to a smartphone. However, this technology is dependent on integrating sensor, battery and wireless communication devices, both complex and expensive. The SERS technique, on the other hand, could simplify matters significantly as remote sensing is based on optical measurement.

The team, from the University of Houston and colleagues in Korea, developed a small device built from multiple layers of gold nanowires stacked on top of a gold film and produced using solvent-assisted nanotransfer printing (S-nTP) for the reliable formation of plasmonic nanostructures on a contact lens. This optimized Raman scattering to take advantage of the technique’s ability to identify molecular samples. The device improves upon these sensing properties by producing “hot spots”, narrow gaps within the nanostructure that work to intensify the Raman signal.

The 3D stacking of plasmonic nanostructures used the S-nTP technique to provide these extremely dense and regular hot spot arrays for highly sensitive SERS analysis. Moreover, hybrid plasmonic nanostructures obtained by printing the nanowires on a continuous metal film or graphene surface show significantly intensified SERS signals due to vertical plasmonic coupling.

Despite most nanofabrication techniques depending on a hard substrate such as glass or a silicon wafer, this study used a flexible nanostructure, with the layered nanoarray being produced on a hard substrate before being lifted off and printed on a soft contact. As the concentration of glucose in human tears is very low, plasmonic nanostructures made of Au were positioned on to the surface of the contact lens for the trace-amount glucose detection.

Although non-invasive glucose sensing is just one potential application, the study offered a useful means of proving the technology, and also showed that the versatile printing capability on diverse surfaces could realize unique SERS platforms to provide superior convenience and accuracy of measurement. In terms of applications, the concept could also find uses in non-invasive biomedical diagnoses such as sweat sensors. As a next step, the team are looking to demonstrate the applicability of retina-safe laser excitation for glucose detection.