Magnetically controlled microrobotic system for programmable stiffness tuning and active steering of microcatheters.

Surgical tasks in small tortuous lumens demand interventional instruments with controllable mechanical adaptability. However, current microcatheters lack a non-disruptive, integration-ready strategy for dynamic stiffness tuning-critical for meeting the divergent mechanical demands for compliant steering and stable advancement. Here, we present a microrobotic system based on a helix-shaped magnetic soft microrobot (Helixoft) that compatibly integrates with commercial microcatheters (down to 300 μm in diameter), enabling continuous stiffness tuning (up to 40-fold) and precise steering, both controlled magnetically, free of any other potentially harmful stimuli. Stiffness tuning and active steering are independently controlled via a decoupled control strategy by the helical motion and torque-driven bending of independent microrobot components. This stiffness and structure reconfiguration allow the integrated microcatheter to perform large-angle navigation, precision payload delivery, and localised tissue biopsy without unintended buckling or tissue damage. We validate the system in both ex-vivo oviduct biopsy and in-vivo drug delivery to the fourth-generation bronchi of live pigs. The Helixoft system provides a minimally disruptive robotic strategy for the mechanical reconfiguration in confined and sensitive luminal environments.