In this paper, a design method for a Soft Micro-Robot (SMR) used for medical intervention in the context of cochlear implant insertion is proposed. Optimal design of cochlear implants has been a highly active research area in recent years. Dozens of articles address the topic of optimal design using different actuation strategies, resulting overall in promising outcomes. From magnetic to fluid actuation and concentric tubes, current strategies are based on generating an optimal bending moment. However, this approach gives optimal results that cannot be manufactured. Considering the manufacturing constraints of micro-scale soft robots, an optimal design method based on varying the robot bending stiffness is studied here. The cochlear implant is actuated by a tendon and has an optimal bending stiffness to achieve a given objective. In the context of cochlear insertion, this objective is to minimize the root mean square error (RMSE) of the robot neutral axis in comparison to the cochlea helically shaped center-line. Simulation results are promising with an average distance error of 392μm and a standard-deviation of 33μm considering the robot material and manufacturing uncertainties.