A novel flexible catheter with integrated magnetic variable stiffness and actuation

Flexible instruments offer significant advantages over traditional rigid instruments in ophthalmic surgery, because they can achieve larger working space and minimize the risk of damage caused by contact with eye tissues. However, it also needs to be rigid to achieve sufficient surgical operation force and stability. In this study, we propose a novel flexible catheter with integrated magnetic variable stiffness and actuation, based on electromagnetic induction heating and phase change alloy. The experimental results show that the catheter can switch from rigid to flexible modes in 11 s, and it takes 10 s to switch from flexible to rigid modes in room temperature. The bending stiffness of the catheter is 930.23°N mm² in rigid mode and 74.42°N mm² in flexible mode. In addition, the catheter can limit the axial force below 0.08°N in flexible mode, while withstand a force greater than 1.08°N in rigid mode. The catheter is equipped with a magnetic tip that can safely navigate in flexible mode with maximum bending angle of 106 degrees. The phantom experimental results demonstrated the potential clinical value of the proposed catheter.