This illustration shows the schematic procedure for the fabrication of a surface-enhanced Raman scattering contact lens via transfer printing.

Blood testing is the standard option for checking glucose levels, but a new technology could allow noninvasive testing via a contact lens that samples glucose levels in tears. Glucose is a good target for optical sensing, and especially for what is known as surface-enhanced Raman scattering spectroscopy.

Researchers have developed a tiny device, built from multiple layers of gold nanowires stacked on top of a gold film and produced using solvent-assisted nanotransfer printing. The nanotransfer printing optimizes the use of surface-enhanced Raman scattering to take advantage of the technique’s ability to detect small molecular samples. The device enhances the sensing properties of the technique by creating “hot spots,” or narrow gaps within the nanostructure, which intensify the Raman signal.

The researchers found that the structure is an effective mechanism for using surface-enhanced Raman scattering spectroscopy. Although traditional nanofabrication techniques rely on a hard substrate — usually glass or a silicon wafer — the researchers wanted a flexible nanostructure, which would be more suited to wearable electronics. The layered nanoarray was produced on a hard substrate but lifted off and printed onto a soft contact.