Control of Manufacturing Process of Soft Actuator Made of Magnetorheological Elastomer

Abstract

Microscale soft actuators can be used in medical catheters and guidewires for active steering, which can reduce the procedure time and the risk of infection in vascular interventions. Pressure-driven soft actuators have a simpler structure than other mechanisms because they have a single asymmetric shape and can be made of a single material. Pressure-driven soft actuators are, therefore, suitable for microscale miniaturization, and considerable research on applying pressure-driven soft actuators to medical micro-guidewires has been conducted. Closed and open molding have been proposed as methods for fabricating pressure-driven soft actuators. However, it is difficult to control the diameter and the degree of asymmetry of the produced actuators due to the effect of microbubbles and surface tension during the manufacturing process. This paper proposes a novel fabrication method to control the degree of asymmetry using the magnetic field and dip coating the magnetorheological elastomer. The diameter is controlled by adjusting the precuring time of MR-elastomer and the travel speed of the inner mold during manufacturing. The degree of asymmetry is controlled independently by controlling the current of the electromagnet. The manufacturing process and the parameters are modeled to control the outer diameter and the eccentricity of the resulting actuators. The manufacturing parameters are experimentally controlled to ensure consistency in the fabrication of the actuators. Specifically, the manufacturing system is controlled to produce actuators with a diameter of 0.7 mm and an eccentricity of 80 μm with errors of 1.7% and 3.75%, respectively. The fabricated microscale pressure-driven actuators can bend sharply up to 115° for a length of 5.41 mm.