An active matrix electrowetting on dielectric (AM-EWOD) device which 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 a top substrate electrode and a drive electrode between which the one or more droplets may be positioned; circuitry configured to write data to the corresponding array element by selectively applying to the drive electrode either: (i) a time-varying voltage waveform V1 of amplitude VB and period t0; or (ii) a time-varying voltage waveform V2, the logical inverse of V1, and applying to the top substrate electrode the time-varying voltage waveform V2+Voffset, where Voffset represents an offset voltage signal which may have AC and/or DC components and may equal zero.