A method of driving an active matrix electro-wetting on dielectric (AM-EWOD) device with an alternating sign of actuation voltage, the AM-EWOD device comprising a plurality of array element electrodes (38, 38A,38B) defining respective array elements and a reference electrode, the method comprising: (i) setting the reference electrode to a first reference voltage; (ii) writing a set of data to array element electrodes (38,38A,38B) of array elements of the device, whereby an array element is put into an actuated state if a first data voltage is written to the corresponding array element electrode (38,38A,38B) to define a voltage difference of magnitude equal to or greater than an actuation voltage and having a first sign across the array element and is put into a non-actuated state if a second, different data voltage is written to the corresponding array element electrode; (iii) either: (a) maintaining the voltages written to the array element electrodes (38,38A,38B) in feature (ii) until a time to or (b) re-writing N-1 times where N ≧ 2 the set of data to the array element electrodes (38,38A,38B) of the array elements; (iv) setting the reference electrode to a second reference voltage different from the first reference voltage; (v) writing another set of data to array element electrodes (38,38A,38B) of at least some array elements of the device whereby an array element is put into the actuated state if a third data voltage is written to the corresponding array element electrode to define a voltage difference of magnitude equal to or greater than the actuation voltage and having a second sign opposite to the first sign across the array element and is put into the non-actuated state if a fourth, different data voltage is written to the corresponding array element electrode; and (vi) either: (a) maintaining the voltages written to the array element electrodes element in feature (v) until a time t 1 or (b) re-writing M-1 times where M ≧ 2 the another set of data to the array element electrodes (38,38A,38B) of the at least some array elements; wherein the second reference voltage is of opposite sign to the first reference voltage. (i) setting the reference electrode to a first reference voltage; (ii) writing a set of data to array element electrodes (38,38A,38B) of array elements of the device, whereby an array element is put into an actuated state if a first data voltage is written to the corresponding array element electrode (38,38A,38B) to define a voltage difference of magnitude equal to or greater than an actuation voltage and having a first sign across the array element and is put into a non-actuated state if a second, different data voltage is written to the corresponding array element electrode; (iii) either: (a) maintaining the voltages written to the array element electrodes (38,38A,38B) in feature (ii) until a time to or (b) re-writing N-1 times where N ≧ 2 the set of data to the array element electrodes (38,38A,38B) of the array elements; (a) maintaining the voltages written to the array element electrodes (38,38A,38B) in feature (ii) until a time to or (b) re-writing N-1 times where N ≧ 2 the set of data to the array element electrodes (38,38A,38B) of the array elements; (iv) setting the reference electrode to a second reference voltage different from the first reference voltage; (v) writing another set of data to array element electrodes (38,38A,38B) of at least some array elements of the device whereby an array element is put into the actuated state if a third data voltage is written to the corresponding array element electrode to define a voltage difference of magnitude equal to or greater than the actuation voltage and having a second sign opposite to the first sign across the array element and is put into the non-actuated state if a fourth, different data voltage is written to the corresponding array element electrode; and (vi) either: (a) maintaining the voltages written to the array element electrodes element in feature (v) until a time t 1 or (b) re-writing M-1 times where M ≧ 2 the another set of data to the array element electrodes (38,38A,38B) of the at least some array elements; wherein the second reference voltage is of opposite sign to the first reference voltage. (a) maintaining the voltages written to the array element electrodes element in feature (v) until a time t 1 or (b) re-writing M-1 times where M ≧ 2 the another set of data to the array element electrodes (38,38A,38B) of the at least some array elements; wherein the second reference voltage is of opposite sign to the first reference voltage.