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If a perforation occurs as a result of a flexible endoscopic procedure, suturing through urgent laparoscopy or open surgery may be required to repair the perforation because suturing is normally stronger than closure using existing endoscopic devices. Suturing with stitches and knots, widely adopted in open or laparoscopic surgery, is still not possible in flexible endoscopy. This is because of the confined space of the natural orifice and target area, high levels of motion dexterity and force needed for stitching and knot-tying, and critical size and strength requirements of wound closure. We present a novel flexible endoscopic robotic suturing system that is able to suture gastrointestinal defects without opening up the patient's body like in open or laparoscopic surgery. This system features a robotic needle driver and a robotic grasper, both of which are flexible, through-the-scope (small in sizes), and dexterous with five degrees of freedom. The needle driver, facilitated by the grasper, enables the surgeon to control a needle through teleoperation to make stitches and knots in flexible endoscopy. Successful in vivo trials were conducted in the rectum of a live pig to confirm the feasibility of endoscopic suturing and knot-tying using the system in a realistic surgical scenario (not possible with existing devices which are all manually driven). This new technology will change the way how surgeons close gastrointestinal defects.

In flexible endoscopy, the endoscope needs to be sufficiently flexible to go through the tortuous paths inside the human body and meanwhile be stiff enough to withstand external payloads without unwanted tip bending during operation. Thus, an endoscope whose stiffness can be adjusted on command is needed. This paper presents a novel variablestiffness manipulator. The manipulator (Ø15 mm) has embedded thermoplastic tubes whose stiffness is tunable through temperature. Temperature is adjusted through joule heat generated by the electrical current supplied to the stainless steel coils and an active aircooling mechanism. Tests and modeling were conducted to characterize the performance of the design. The manipulator has a high stiffness-changing ratio (22) between rigid and flexible states while that of its commercial Olympus counterpart is only 1.59. The active cooling time is 11.9s while that of passive ambient cooling is 100.3s. The thermal insulation layer (Aerogel) keeps the temperature of the outer surface within the safe range (below 41˚C). The models can describe the heating and cooling processes with root mean square errors ranging from 0.6 ˚C to 1.3 ˚C. The results confirm the feasibility of a variable-stiffness endoscopic manipulator with high stiffness-changing ratio, fast mode-switching, and safe thermal insulation.

Variable stiffness for robotics are attracting increasing attention from researchers, especially in the surgical field. A surgical robot that can access the human colon or stomach via natural orifices must be flexible enough to pass through tortuous paths and to work in a confined space. Meanwhile, the robot must also be stiff enough to ensure pushability and to hold payloads during the surgery. Thus, a surgical robot which allows active stiffness control is desirable. This paper presents a new design concept for variable stiffness manipulators using a thermoplastic material-Polyethylene Terephthalate (PET)-and a flexible stainless steel sheath as a heating solution. The stiffness of PET can be significantly adjusted through temperature. Experiments and validations are carried out at different conditions. The results show that our proposed design is at least as flexible as a typical commercial endoscope when flexibility is desired and meanwhile at least 9 times stiffer than the endoscope when stiffness is desired. A tendon-driven manipulator based on the proposed concept was also developed. Validation tests showed that the manipulator in compliant mode can be significantly bend through cable actuation, and the manipulator in stiff mode can hold its shape against considerably large loads.