A Pop-Up Soft Robot Driven by Hydraulic Folded Actuators for Minimally Invasive Surgery

The incidence rate of colorectal cancer ranks third among all cancers, which is a serious threat to human health [1]. Endoscopic submucosal dissection (ESD) is an effective endoscopic surgical method for early gastric and colorectal cancers [2]. However, ESD is a procedure with high technical requirements, which brings a higher risk of complications and requires long training for clinicians [3]. Robots are expected to simplify ESD procedures and reduce training time. But there is no standard flexible robotic endoscope at present. Soft robots can potentially offer better adaptability and safer interaction with the environment. As such, they hold great potential in solving the technical challenges of the current minimally invasive surgery (MIS), which are difficult to be solved by rigid robots. Here we demonstrate an inflatable robot which is largely made of flexible plastic film. In the deflated state, it is easy to collapse, fold and roll into a small size, promising easier delivery by a carrier endoscope to the proximal colon. After reaching the target site, the robot is inflated and the surgery is performed. This work is based on the inflatable Cyclops robot [4][5]. However, small folded hydraulic actuators are used to replace the contraction-based pouch actuators used in [5], which have a larger size. The anchor points of the cables with planar layout replace the spatial layout in [4], which reduces the axial size of the robot, allowing it to pass through the colon bends more easily. Folded actuators made of an airbag are flexible and adaptable [6]. The actuator volume is very small under deflated condition, but it can achieve large deformation after inflation. The proposed actuator uses a folded chamber to pull the cable to produce a large displacement without the need of displacement amplification mechanisms. In the deflated state, the length of soft scaffold of the robot is about 65mm, and the overall size of the robot is 100mm ×6mm×20mm. In the state of inflation, the soft scaffold deploys into a hexagonal prism with a length of 55mm, and the bottom side length of the prism is 30mm. The tip workspace of the robot can reach 40mm in all three directions of the local coordinate system.