US Patent 9458543 Active matrix electrowetting-on-dielectric device

An active matrix electrowetting on dielectric (AM-EWOD) device includes a plurality of array elements configured to manipulate one or more droplets of fluid on an array, each of the array elements including a corresponding array element circuit. Each array element circuit includes write circuitry configured to write data to the corresponding array element for controlling the manipulation of the droplets of fluid, and sensor circuitry configured to sense an impedance present at the corresponding array element. The sensor circuitry is configured to operate in one of a normal mode of sensitivity for detection of a droplet, or a high mode of sensitivity to detect an electric property of an array element hydrophobic surface. The sensor circuitry includes an active element, such as an active capacitor or active transistor, and a capacitance across the active element is different in the normal sensitivity mode as compared to the high sensitivity mode.