Integration of leaky waveguide detection with electrowetting on dielectric digital microfluidic devices

Typically, Electrowetting on dielectric (EWOD) digital microfluidic devices consist of an array of metal electrodes covered with a continuous hydrophobic dielectric layer. The monitoring of droplet position and detection in EWOD is usually achieved via microscopy, thereby resulting in increasing the size and complexity of the instrumentation associated with such devices. This work for the first time demonstrates that metal clad leaky waveguide (MCLW) is suitable for detection in EWOD devices. MCLW devices typically consist of a metal layer covered with a dielectric layer in which the leaky waveguide mode propagates. The two structures are fundamentally compatible provided the metal and dielectric layer thicknesses and refractive indices can be optimised to permit both electrowetting and waveguiding. In this work, it has been shown that titanium electrodes covered with a fluoropolymer layer can be used to perform MCLW detection of droplets on EWOD platforms.