Design, characterization and optimization of a soft fluidic actuator for minimally invasive surgery.

Purpose: In minimally invasive surgery and endoscopy, the rise of soft robotics, using materials of similar softness as biological soft tissues, opens many new opportunities. Soft actuated catheters could become an alternative to current steerable catheters, by minimizing the risk of damage to surrounding tissues while enhancing the possibilities to navigate in confined space and to reach remote locations. Fluidic actuators present the advantage to be safe, since they do not require rigid parts nor voltage, to be lightweight, and to allow the reduction of the number of parts needed for a given movement. This work presents the design, development and characterization of a soft fluidic bending actuator for a steerable catheter.

Methods: A silicone prototype of 5 mm diameter has been designed. It has one degree of freedom in bending and achieves a radius of curvature below 10 mm. A numerical model has been developed and compared to the experimental results.

Results: Despite an overestimation of the bending, the numerical model properly captures the behaviour of the actuator. This allowed to identify and validate the key design parameters of the actuator, namely the ratio between the pressure channel surface and the actuator cross-section surface. Based on the results, an optimized design has been developed and numerically implemented. The miniaturization and the potential to carry devices with non-negligible bending stiffness have also been discussed.

Conclusion: In this work, a proof of concept of a soft fluidic actuator for a steerable catheter has been designed, developed and characterized. It showed promising results concerning the feasibility of a miniaturized actuator with two degrees of freedom.