Characterization of sensing capability of optofluidic ring resonator biosensors

The sensing capability of the capillary-based optofluidic ring resonator in bulk refractive index (RI) detection and label-free small molecule detection is investigated. In bulk RI detection, a sensitivity of 570 nm/refractive index units (RIU) is achieved with a Q-factor of 1.2x10(5). A change of 2.8x10(-7) RIU is observed with the noise equivalent detection limit (NEDL) of 3.8x10(-8) RIU. In small molecule detection, 10 nM biotin is detected with surface mass density of 1.6 pg/mm(2). The NEDL is approximately 0.14 pg/mm(2). These results set the benchmark for ring resonator sensing performance and compare very favorably with those obtained with other label-free optical sensors. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3462296]