Nanofabricated refractive index sensor based on photon tunneling in nanofluidic channel

We have fabricated and tested a refractive index sensor based on photon tunneling in a nanofluidic system. The device comprises an extremely thin fluid chamber formed between two optically transparent layers. It can be used to detect changes in refractive index due to chemical composition changes of a fluid in the small test volume. Because the physical property measured is a refractive index change, no staining or labeling is required. We tested the device with five samples, water and water with 1% ethanol, 2% ethanol, 5% ethanol and 10% ethanol. The sensing was done by measuring the intensity of a reflected laser beam incident on the sensing element at around the critical angle. The measured response agrees well with the calculated reflectance.