A microfluidic system comprising: an electro-wetting on dielectric (EWOD) device comprising an element array configured to receive one or more fluid droplets, the element array comprising a plurality of individual array elements; and a control system (38,72) configured to control actuation voltages applied to the element array to perform manipulation operations as to the fluid droplets; wherein: the control system is configured to apply a sequence of actuation voltages to a portion of the array elements associated with a droplet, the portion comprising a plurality of array elements and being fixed over time; the control system (38,72) is configured to apply the sequence of actuation voltages commonly to the plurality of array elements to restrict deviation of the droplet from a desired droplet state, the desired droplet state comprising droplet position or droplet shape; and the sequence of actuation voltages includes actuation-on periods in which the plurality of array elements associated with the droplet is commonly actuated and actuation-off periods in which the plurality of array elements associated with the droplet is commonly not actuated, and the actuation-off periods are non-zero, the actuation-on periods alternating with the actuation-off periods. an electro-wetting on dielectric (EWOD) device comprising an element array configured to receive one or more fluid droplets, the element array comprising a plurality of individual array elements; and a control system (38,72) configured to control actuation voltages applied to the element array to perform manipulation operations as to the fluid droplets; wherein: the control system is configured to apply a sequence of actuation voltages to a portion of the array elements associated with a droplet, the portion comprising a plurality of array elements and being fixed over time; the control system (38,72) is configured to apply the sequence of actuation voltages commonly to the plurality of array elements to restrict deviation of the droplet from a desired droplet state, the desired droplet state comprising droplet position or droplet shape; and the sequence of actuation voltages includes actuation-on periods in which the plurality of array elements associated with the droplet is commonly actuated and actuation-off periods in which the plurality of array elements associated with the droplet is commonly not actuated, and the actuation-off periods are non-zero, the actuation-on periods alternating with the actuation-off periods. the control system is configured to apply a sequence of actuation voltages to a portion of the array elements associated with a droplet, the portion comprising a plurality of array elements and being fixed over time; the control system (38,72) is configured to apply the sequence of actuation voltages commonly to the plurality of array elements to restrict deviation of the droplet from a desired droplet state, the desired droplet state comprising droplet position or droplet shape; and the sequence of actuation voltages includes actuation-on periods in which the plurality of array elements associated with the droplet is commonly actuated and actuation-off periods in which the plurality of array elements associated with the droplet is commonly not actuated, and the actuation-off periods are non-zero, the actuation-on periods alternating with the actuation-off periods.