Fig. 3: Distributed stiffness control with a dual-segment stiffness tuning module.

a Strategy for estimating resistive torque to enable independent helix control. Error bars represent standard deviation, n = 3 times, mean ± sd. The pink circle represents the actuation zone corresponding to \({T}_{{{{\rm{m}}}}} > {T}_{{{{\rm{resist}}}}}\). b Independent control of two helices in a single microcatheter. The orange and blue arrows indicate the motion directions of the first and second helices, respectively. c Multiple bending configurations of the corresponding microcatheter. The blue line indicates the shape of the microcatheter. Scale bar: 5 mm.