Magnetorheological-Elastomer-Based and Hydraulically Steerable Actuator for Micro Guidewire and Catheter

The pressure-driven mechanisms for steerable guidewires and catheters are difficult to fabricate when miniaturized to submillimeter-scale. Micro bubbles resulting from molding or surface irregularities due to surface tension can affect the actuation performance as the outer diameter of the pressure-driven actuator decreases to the submillimeter-scale. This paper presents a novel fabrication method to manufacture pressure-driven actuators of submillimeter-scale. The proposed fabrication method utilizes magnetorheological (MR) elastomer and magnetic field to determine the geometric dimensions of the actuator with micro-scale precision. An actuator of the diameter of 0.7 mm and the eccentricity of $80~\mu $ m is designed and fabricated with absolute errors of $12~\mu $ m and $3~\mu $ m, respectively. The steering performance of the fabricated micro actuator is tested through experiments. The actuator can achieve a sharp bending angle of 124 degrees with a length of 5.41 mm, by optimizing the eccentricity through the finite-element analysis.