Cochlear implants can be successfully used to reduce the inner ear profound deafness. The implant is inserted into the inner ear by the surgeon’s hand. Because the cochlea has a spiral-like structure (cochlear duct), the insertion of the implant is often difficult, furthermore the basilar membrane could be easily damaged. One of the aims of our investigation is to develop a mathematical model based an synthesis method for implants with hydraulic actuation. This hydraulic actuation, which is integrated in the implant, facilitates the insertion of the implant structure to the shape of cochlear duct. Thus, the implant can follow the spiral-shaped cochlear duct without damaging the sensitive tissue of the basilar membrane. Some examples for hydraulic actuated cochlear implants based on compliant mechanisms technology are presented in this paper.