Surgical instruments with articulating shafts

Various example embodiments described herein are directed to articulating surgical instruments for treating tissue comprising an end effector and a shaft extending proximally from the end effector along a longitudinal axis. In certain embodiments, the shaft comprises a plurality of transverse spacer members as well as first and second rotatable members extending through at least a portion of the plurality of transverse spacer members. The first and second rotatable members may both be biased away from the longitudinal axis such that their respective directions of bias vary with rotation of the first rotatable member. When the respective directions of bias of the first and second rotatable members oppose one another, the shaft may be substantially straight. When the respective directions of bias of the first and second rotatable members are aligned with one another, the shaft may articulate away from the longitudinal axis in the direction of the alignment.