Designing micro- and nanostructures for artificial urinary sphincters

The dielectric elastomers are functional materials that have promising potential as actuators with muscle-like mechanical properties due to their inherent compliancy and overall performance: the combination of large deformations, high energy densities and unique sensory capabilities. Consequently, such actuators should be realized to replace the currently available artificial urinary sphincters building dielectric thin film structures that work with several 10 V. The present communication describes the determination of the forces (1 - 10 N) and deformation levels (similar to 10%) necessary for the appropriate operation of the artificial sphincter as well as the response time to master stress incontinence (reaction time less than 0.1 s). Knowing the dimensions of the presently used artificial urinary sphincters, these macroscopic parameters form the basis of the actuator design. Here, we follow the strategy to start from organic thin films maybe even monolayers, which should work with low voltages but only provide small deformations. Actuators out of 10,000 or 100,000 layers will finally provide the necessary force. The suitable choice of elastomer and electrode materials is vital for the success. As the number of incontinent patients is steadily increasing worldwide, it becomes more and more important to reveal the sphincter's function under static and stress conditions to realize artificial urinary sphincters, based on sophisticated, biologically inspired concepts to become nature analogue.