Variable-stiffness Continnum Manipulators

In flexible endoscopic procedures, the endoscope needs to have sufficient flexibility to pass through tortuous paths and to be operated in a confined space. In addition, it should also possess an acceptable stiffness to hold the payloads when working with the target tissue. We developed a new design concept for variable stiffness manipulators using thermoplastic material Polyethylene Terephthalate (PET) and a flexible stainless steel sheath as a heating media. The stiffness phases of PET can be actively adjusted through temperature. A tendon-driven flexible robotic arm integrated with a variable stiffness spine was also developed, and ex vivo tests on fresh porcine tissue were conducted. The manipulator in compliant mode can be easily controlled through the tendons, and it is able to hold its shape against considerably large loads in stiff mode. The results demonstrate not only the high potential of the design concept for the future medical application but also the first steps toward building a complete surgical robotic system with fully controlled variable stiffness.

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