A Soft Inflatable Robot Driven by Hydraulic Folded Pouch Actuators for Minimally Invasive Surgery

This paper presents a soft, inflatable, cable-driven parallel robot (CDPR) for Minimally Invasive Surgery. The CDPR has 5 degrees of freedom and is driven by 6 cables and 6 hydraulic folded actuators. The actuator utilizes a folded chamber to pull a cable. The robot comprises a soft hexagonal variable-stiffness scaffold with a welded internal triangular support, which increases the stiffness of the robot when pressurized. The fabrication methodology is demonstrated in detail. A test platform is designed to obtain the characteristics of the folding actuator. The relationship between input liquid volume and actuator displacement can be predicted well by a geometry-based method. The displacement output of the actuator can reach 22 mm, which is nearly twice its length in its zero-volume folded state. Robot repeatability tests show mean and root mean square errors below 0.3 mm. The robot is made from plastic laminate sheets of thickness 120 μm and can deploy from 100 mm in length and 14 mm in diameter when folded, into an inflatable hollow hexagonal prism with 29 mm side length and 78 mm edge length. Deployment in a colon phantom is demonstrated and simulated surgery is conducted to validate the robot performance.