  A microfluidic whispering gallery mode (WGM) biosensing system is proposed
for enhanced delivery and detection of target molecules. A microtoroid
resonator coupled to a tapered optical fiber is immersed within a microfluidic
channel, and supplied with target molecules at various flow rates. We show
through Monte Carlo simulations that the flow characteristics and resonantly
enhanced optical forces of the sensor substantially improve both the sensing
time and yield. When compared to a diffusion-limited sensing modality, the
average time required to detect a single molecule is reduced from more than 100
minutes to less than 10 seconds, and the overall yield of the device is
enhanced from less than 5% to a maximum of 70.6% for femtomolar concentrations
of analyte.
