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Chen et al. Soft Sci. 2026, 6, 48 Page 13 of 19

Figure 4. Magnetic deflection and navigation performance of the MBF. (A) Experimental and finite element simulation results of the
deflection angle θ of the MBF with different field strength B and angle α; (B) Comparison of experiments and simulations at magnetic field
angle α = 90°; (C) Comparison of the deflection angle of the MBF with and without the phase-change balloon, demonstrating the minimal
impact of the balloon on navigation performance; (D) Accessibility test of the MBF in planar channels, showing successful navigation
through all four channels under external magnetic fields; (E) Accessibility test of the commercial guidewire with a straight tip in planar
channels, showing no accessibility to all channels; (F) Accessibility test of the commercial guidewire with J-shaped tip in planar channels,
showing partial accessibility to only channels 1 and 3. For quantitative experimental data, error bars represent the standard deviation (SD),
with n = 3 independent replicates. MBF: Magnetic balloon fiberbot; Exp.: experiment; Sim.: simulation.

To assess the MBF’s ability to navigate through complex branches of small arteries, we conducted
accessibility tests in a planar model with four 2-mm-wide channels (labeled as channels 1, 2, 3, 4). As
illustrated in Figure 4D, the MBF successfully accessed all four channels under the guidance of an external
magnetic field, demonstrating its ability to navigate complex and narrow pathways. To further quantify this
navigation performance, we conducted 10 repeated trials for representative branching paths and summarized
the operation time, success rate in Supplementary Figure 12. In stark contrast, commercial guidewires with a
straight tip [Figure 4E] or a J-shaped tip [Figure 4F] exhibited limited accessibility. The straight tip guidewire
was stuck at the entrance and unable to navigate through any channels, while the J-shaped tip guidewire
showed partial accessibility to channels 1 and 3 but failed to navigate to channels 2 and 4. These results
underscore the MBF’s superior navigation capabilities compared to conventional guidewires, particularly in
environments with narrow and tortuous pathways, as detailed in Supplementary Video 2.