Effect of curvilinear insertion on mechanics of curved needles in tissue-mimicking material

Needle steering to achieve large curvatures and deflection has the potential to enhance percutaneous procedures, such as brachytherapy, radiofrequency ablation, and deep brain stimulation. However, the mechanics of needles with large curvatures still need to be explored. This study introduces a curvilinear insertion to comprehensively investigate needle-tissue interactions. Experiments using passive curved needles with various bent angles (7.5°, 15°, 22.5°, and 30°) are conducted in tissue-mimicking materials, comparing curvilinear and linear insertion techniques. The curvilinear insertion method significantly reduces the average transverse force by 55.76%, axial force by 45.87%, and bending moment by 57.36%. Additionally, the proposed method achieves comparable curvature with less needle tip displacement between the initial puncture and the final needle position. These reductions in force, moment, and displacement may result in minimizing tissue damage and tissue deformation. The findings suggest that curvilinear insertion offers mechanical advantages and provides valuable insights for developing advanced needles with large curvature, enabling more precise targeting in minimally invasive surgery.