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Jamming is a phenomenon in which a collectionof compliant elements is encased in an airtight envelope, anda vacuum-induced pressure enhances frictional and kinematiccoupling, resulting in dramatic changes in stiffness. This paperintroduces the jamming of square cross-sectioned fibers, whichallow for tunable and programmable anisotropic stiffness. Atheoretical model captures the effect of major geometric designparameters on the direction-variant bending stiffness of theselong and slender jamming elements. The model is experimen-tally validated, and a 13-fold stiffening in one direction anda 22-fold stiffening in the orthogonal direction is achievedwith a single jamming element. The performance of a square-fiber-jamming continuum robot structure is demonstrated in asteering task, with an average reduction of 74% in the measuredinsertion force when unjammed, and a direction-variant 53%or 100% increase in the measured tip stiffness when jammed. 

Flexures provide precise motion control without friction or wear. Variable impedance mechanisms enable adapt- able and robust interactions with the environment. This paper combines the advantages of both approaches through layer jamming. Thin sheets of complaint material are encased in an airtight envelope, and when connected to a vacuum, the bending stiffness and damping increase dramatically. Using layer jamming structures as flexure elements leads to mechan- ical systems that can actively vary stiffness and damping. This results in flexure mechanisms with the versatility to transition between degrees of freedom and degrees of constraint and to tune impact response. This approach is used to create a 2-DOF, jamming-based, tunable impedance robotic wrist that enables passive hybrid force/position control for contact tasks.