Disposable Fluidic Self-Propelling Robot for Colonoscopy

Abstract

Colon cancer, the second leading cause of cancer deaths in the U.S., is curable if detected at early stages. To inspect the colon for polyps or cancerous cells, standard colonoscopy is performed by inserting a long, flexible colonoscope. Conventional colonoscopy is slow, painful, and requires sedation and insufflation. Maneuvering difficulty, possibility of loop formation, risk of tissue perforation, and a steep learning curve for surgeons are other issues with manual colonoscopy. Fusion of robotics and endoscopy is paving the way to automate this procedure to reduce trauma and discomfort to patients and facilitate wide-scale screening.Locomotion is the most challenging part of a robotic design for colonoscopy due to the intrinsic characteristics of the colon. The colon is slippery, naturally collapsed, stretchable, and loosely fixed to surrounding tissue. Many previous designs have used an inchworm approach, wheels, and/or tracks to achieve locomotion [1,2]. However, the main drawbacks of these methods are slow advancement and relatively large friction/contact with the inner wall of the intestine. Capsule endoscopy [3] is another recently developed technology. The capsule moves passively through the gastrointestinal tract without discomfort, eliminating the need for intubation, insufflation, or sedation. The main limitation of this method is inability to control the trajectory of the capsule or to localize an identified lesion. Recently, an external-magnetic-based locomotion controlled by a robotic arm has been developed [4]. This technique involves an additional expensive component (robotic arm) making the procedure less affordable, more complex for training, and longer compared with conventional colonoscopy [4]. Furthermore, due to the external magnetic field, the robotic capsule is always drawn upward to the internal wall of the intestine, creating friction and constant radial contact forces with tissues, increasing the risk of tissue damage and perforation. Here, we present a fluidic self-propelling robot that is less invasive, simple, skill-independent, easy to fabricate, inexpensive, and disposable.The robot is composed of an anal introducer, a latex tube with an inner diameter (ID) and an outer diameter (OD) of 1.6 mm and 3.2 mm, respectively, and a tip, as shown in Fig. 1. One end of the latex tube is tied over the robot's tip and the other end is connected to a poly(vinyl chloride) tube. A small portion of the latex tube is placed between the anal introducer and the tip, and the rest of it is available outside the body. The closed end of the latex tube is prestressed such that when the pressurized air is introduced into the tube, it starts to inflate first from the closed end (the tip) radially to a maximum diameter of 0.63 in. (well below the ID of the large intestine) and then axially. When the anal introducer is kept immobile, the axial expansion of the tube makes the tip of the robot advance forward. As the tip of the robot advances, more latex tube is pulled in from outside the body. This provides a swift, continuous, and long stroke. Figure 2 demonstrates the working principle of this mechanism. The balloon shortens in length by one-third as it deflates. Insofar as the descending colon accounts for almost one-third of the colon's total length, deflation of the balloon retracts the robot tip into the descending colon. Eventually, the robot can be removed by gently pulling it out without undue risk of tissue trauma.To test the functionality of the robot, a colonoscopy simulator was built (seen in Fig. 3). The simulator bed is made of soft foam, simulating the mechanical properties of the tissues surrounding the colon. A 3D channel was cut into the foam, matching the configuration of a real colon according to the anatomical length of the ascending, descending, and transverse colon as shown in Fig. 3. A commercially available synthetic colon (O-LIN-A-0005, SynDaver™ Labs, Tampa, FL), emulating the mechanical proper