The invention relates to actuators based on electroactive polymeric materials for use in pumping fluids or in other applications where a contractile actuation is required, in particular although not necessarily exclusively for use in vascular pulsation devices such as a variable aortic tension device. Embodiments disclosed include an actuator ( 10) comprising: an inner tubular structure (15, 12); an outer tubular structure (13, 14) surrounding the inner tubular structure ( 5, 12) and comprising a plurality of layers of a dielectric elastomeric material ( 13) and a tubular elastic support structure ( 14), the elastic support structure (14) configured to maintain a pre-stress in the layers of the dielectric elastomeric material (13), wherein the outer tubular structure (13, 14) is configured to contract in a radial direction around the inner tubular structure (12, 15) upon application of an actuation voltage signal across the dielectric elastomeric material layers (13).