Surgical tasks in small tortuous lumens demand interventional instruments with controllable mechanical adaptability. Current microcatheters lack a non-disruptive, integration-ready strategy for dynamic stiffness tuning, which cannot meet the divergent mechanical demands for compliant steering and stable advancement.

In a study published in Nature Communications, a research team led by Prof. XU Haifeng at the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences developed a microrobotic system based on a helix-shaped magnetic soft microrobot, the Helixoft.

The Helixoft system is specifically designed for the navigation within narrow and sensitive luminal environments by miniaturising the variable-stiffness catheter to a diameter of 300 μm. This microrobotic system has tunable mechanical performance at the microscale by harnessing the microscale helical motion at the component level to dynamically modulate the otherwise static mechanical properties of the overall structure under a magnetic field.

By combining helical motion with torque-driven bending of individual microrobotic components, independent remote tuning of stiffness and active steering was achieved through a decoupled magnetic control strategy. The functions were achieved solely through magnetic control and without the reliance on potentially harmful external stimuli such as thermal, optical, or electrical inputs.

The Helixoft microcatheter enables independently controlled, multi-segment stiffness tuning, and can be seamless integrated into auxiliary microsurgical tools including mini-cameras, electrodes, and laser fibres, supporting real-time imaging, tissue ablation, and multimodal minimally invasive procedures. Experiments on animal models and systematic safety evaluations confirm the feasibility and biocompatibility of the Helixoft system.

This study provides a minimally disruptive robotic strategy for the mechanical reconfiguration in confined and sensitive luminal environments.

Helixoft microrobotic system for stiffness tuning and active steering of microcatheters during interventional surgeries. (Image by SIAT)