Shape Memory Alloy Spring-Based Force Sensing System for Dual-Sheath Surgical Needle

Abstract

This study presents a dual-sheath needle system integrating miniaturised shape-memory alloy (SMA) springs for simultaneous mechanical actuation and force sensing in minimally invasive medical procedures. The wasp-inspired biomimetic design incorporates two needle segments operating with a 90° phase offset, enabling alternating insertion motion while reducing peak forces. Each segment integrates NiTi SMA springs that function as both return mechanisms and piezoresistive force sensors with Wheatstone bridge signal conditioning. A comprehensive simulation incorporating manufacturing variations, measurement noise, and tissue interaction models validated the system performance under realistic operating conditions. The results demonstrate sub-millinewton resolution 0.71-0.76 mN, high linearity (R2>0.98), strong channel independence (correlation = 0.010), and good signal quality (SNR > 58 dB) across an operating range of 131.4-621.4 mN. Compared with existing SMA force-sensing technologies, the proposed system achieves improved resolution through 73% miniaturisation while providing dual-channel redundancy. The integration of force sensing directly at the needle-tissue interface eliminates the limitations of external sensors and enables real-time feedback for surgical robotics applications, representing an advancement in minimally invasive surgical instrumentation.