Actuators based on electroactive polymer (EAP) hydrogels constitute a very attractive yet poorly explored technology. EAP hydrogels can expand and contract by several times their original volume by application of a small voltage. They can be engineered to be either porous or non-porous and the pore density and distribution can also be controlled. Their inherent limitations of very low actuation speed and need to operate in an aqueous medium constitute no impediment – and in fact make them particularly suitable – to a host of medical applications, some of them with high economic and societal relevance.The Heart-e-Gel project utilises a microsystem concept based on electrode activation to change the volume of EAP hydrogels designed for operation in the cardiovascular system. Given the soft and aqueous nature of these gels and considering the need to accommodate for large volume changes, integrating these materials into complete microsystems poses unique challenges in terms of heterogeneous integration.Heart-e-Gel proposes to target specific medical applications and will require modelling of the microsystem-medical interface as well as assessing the potential of different material, actuation, volume sensing, and system delivery options. Three types of systems of immediate interest in cardiovascular surgery have been selected: a generic occluder for vascular repair, a system for improving endografts/stents for the treatment of abdominal aortic aneurysms, and an adaptable band around the pulmonary artery for patients with congenital heart diseases, or with arteriovenous fistulas.While carrying out the systematic study of EAP hydrogel integration into microsystems, substantial information on processing and characterisation will be gathered and will ultimately lead to a technology library that can enable microsystem designers to address an even wider range of applications.