Nanofabricated refractive index sensor based on photon tunneling in nanofluidic channel

We have fabricated and tested a refractive index sensor based on photon tun neling in a nanofluidic system. The device comprises an extremely thin flui d chamber formed between two optically transparent layers. It can be used t o detect changes in refractive index due to chemical composition changes of a fluid in the small test volume. Because the physical property measured i s 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 intensit y of a reflected laser beam incident on the sensing element at around the c ritical angle. The measured response agrees well with the calculated reflec tance. (C) 2001 Elsevier Science B.V. All rights reserved.