Slender, elastic, robotic manipulators can facilitate minimally invasive surgery (MIS) through nonlinear approaches to a surgical site, circumnavigating obstacles and vital organs. These so-called “continuum robots” have been developed using a variety of structural designs and actuation principles as reviewed in Ref. [1], e.g., tendon-actuated catheters, pneumatic colonoscopies, and concentric-tube steerable needles. However, the compliance that gives these manipulators their dexterity and range of motion also reduces their capacity for force application. Recent research has addressed these problems with new designs, such as the variable stiffness manipulator by Kim et al. [2], but current prototypes are still inferior to conventional rigid tools in their ability to exert external forces.

In this technical brief, we propose a new tendon-driven mechanism consisting of a concatenated series of rigid-link, crossed, four-bar mechanisms that are mechanically constrained to produce uniform, variable curvature motion. The mechanism is unique in that it...

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