High sensitivity sessile droplet resonator for low concentration protein detection

This paper reports a sessile droplet resonator for low concentration protein measurement using a micro-optical-fluidic chip (MOFC). The resonator consists of a sandwiched droplet and two fibers that are placed into the droplet directly. The novel coupling method between optical fibers and droplet that increases the coupling efficiency dramatically, and the total internal reflection inside the droplet insures that the light is mostly trapped in it. The major advantage is that the resonator has high Q-factor, which can be used for low concentration protein measurement. The accuracy of the method reaches 1 × 10^-4 g/mL, which promises for many applications such as disease diagnosis, environmental monitoring and label-free biosensing.