Piezoelectric actuator device

A piezoelectric actuator device comprises a stack (31) of one or more piezoelectric elements (42) defining an external stack boundary and means for applying a voltage across the one or more piezoelectric elements (42), wherein the means includes a pair of opposing electrodes (44a, 44b), first and second channels (32, 34) disposed inward of the external stack boundary and positive and negative conductor members (36a, 36b) received by said first and second channels (32, 34) respectively. The conductor members (36a, 36b) comprise a material that is of liquid behaviour during at least a period of actuator operation.