Recent advances have demonstrated the ability of miniature magnetic crawlers to actively transport cargo in complex and confined systems, such as the GI tract, by leveraging magnetic fields to induce locomotion. For instance, Zhao et al. demonstrated a magnetic origami robot that crawled by in-plane contraction(Ze et al., 2022) where the anisotropic friction on the robot’s feet enabled forward locomotion that can be steered. Nevertheless, the need of anisitropic friction on the feet also precluded bidirectional locomotion in a confined space such as in a lumen without rotation. Other recent works demonstrated entirely-soft crawlers with impressive multi-gait bending locomotion that could transport objects by gripping and direct attachment,(Hu et al., 2018; Wu et al., 2022a; Xu et al., 2022) including cargos 20 times their mass and three times their volume.(Wu et al., 2022b) Nevertheless, integrating the existing crawlers with modular electronics is challenging due to the bulky and rigid nature of electronics that will impede the robot’s bending motions.
Other recent works demonstrated axisymmetric crawler robots with a flexible body and magnetic feet. Importantly, the robots were capable of bidirectional undulatory or inchworm-like locomotion in confined lumens when actuated by an external rotating magnetic dipole.(Pham et al., 2020; Pham and Abbott, 2018; Steiner et al., 2022, 2019) The nonuniform fields of the actuation mechanism could facilitate clinical use, as placing a rotating permanent magnet eliminates the need to surround the patient with coils.[YLK1] [TG2] [YLK3] (Pham and Abbott, 2018) Nevertheless, the crawler lacked a centralized space necessary for functional integration without disrupting the robot’s locomotion.
 [YLK1]This is not specific enough to be meaningful. What is the possible “simplification here” and why that is better than most of the previous crawler?
 [TG2]Reworded. Here is the direct text from Pham2018:
"Our use of a nonuniform field enables the design of the soft robot to be substantially simpler, and as a result enables fabrication at smaller scales. In addition, translating bench-top results that utilize tri-axial Helmholtz coils to a clinical system will be substantially more challenging than translating concepts that utilize nonuniform fields, because it is easier to place a strong magnetic dipole source near and adjacent to a patient than it is to fully surround that patient with coils."
 [YLK3]“substationally more straightforward” is odd – need to reword this.