Droplet-based label-free detection system based on guided-mode resonance and electrowetting-on-dielectric for concentration measurement

We demonstrate a digital microfluidic system with an on-chip detection capability that is based on a guided-mode resonance filter (GMRF). Versatile droplet manipulation was achieved through the electrowetting-on-dielectric (EWOD) technique. GMRF was fabricated through replica molding and soft lithography, and the EWOD chip was fabricated through a typical photolithography process. Droplets measuring 1.125 μL were used to demonstrate merging, mixing, and cutting, and to achieve twofold and Threefold dilutions, and were then transported to the GMRF region for concentration measurement. The bulk sensitivity of GMRF is approximately 90 nm RIU^-1 [17494nm/(g/L)], resulting in a minimum detectable concentration of 4.66 × 10^-5 g/L for a sucrose solution.