Small-scale magnetic soft robotic catheter for in-situ biomechanical force sensing.

Miniaturized magnetic soft robotic catheters offer significant potential in minimally invasive surgery by enabling remote active steering and reduced radiation exposure. However, existing magnetic catheters are limited by the absence of in-situ biomechanical force sensing, which is crucial for controlling the contact force exerted on surrounding tissues during surgical procedures. Here, we report an in-situ force sensing strategy for small-scale magnetic robotic catheters. A coaxial integration of ring-shaped permanent and fibre-based force sensors at the catheter's distal end enables both active steering and precise force measurement. The force sensor is designed to be sensitive exclusively to contact forces perpendicular to its plane, achieving a sensitivity of 0.69 nm/kPa (or 0.38 nm/mN). By manipulating magnetic field patterns, the catheter can actively generate and control contact forces to tissues, using real-time feedback from the force sensor. We demonstrate the system's force-sensing and force-control capability in isolated organs and tissue phantom during passage, verifying the catheter's high force sensitivity and high steerability. The feedback-loop force control enhances procedural safety and efficacy for minimally invasive surgery, making it especially suitable for procedures such as transbronchial microwave ablation of lung nodules and cardiac ablation for atrial fibrillation.