Fig. 3: Locomotion among highly curved routes.
From: Adaptive wireless millirobotic locomotion into distal vasculature
a Physiological requirements on curved lumens with flow speed visualization (including curved routes and bifurcations). The values of radius of curvature Rc and bifurcation angles θb are indicated in the figure. Scale bar: 2 mm. b Effect of lumen’s curvature κ and Φl on the minimum required torque to bend the robot into the curved lumens Tmin (Er = 6.44 MPa). Increasing κ (more curved lumens with smaller Rc or larger θb) and Φl increases Tmin. (c) Snapshots for retrievable curved routes traversing with Rc of 5 mm. The bending torques from the magnetic force Fmag due to the leading position of the magnet, magnetic torque Tmag,z due to the reorientation of the magnet, and the reaction force Freact from the lumen wall due to the rotation of the magnet, overcome Tmin, realizing the curved route traversing. Scale bar: 4 mm. Only the forces and torques enabling the traversing are labeled. d Coordinate system and via-points discretization for curved routes traversing. e Strategies for curved routes traversing (+ and – represent the rotation direction of the magnet around the ya-axis). f Experimental results of robot locomotion speed among various Rc in phantoms C – E (fmag = 0.5 Hz, lmag = 55 mm). The results are consistently around 0.18 mm/s, the one acquired from phantom A. Thus, traversing among curved routes does not sacrifice the locomotion speed. The data are presented as mean values ± standard deviation for the number of trials n = 5.
