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An electric motor applies a torque of 700 N·m to an aluminum shaft, triggering a stable rotation. Two pulleys, B and C, are subjected to torques of 300 N·m and 400 N·m, respectively. The modulus of rigidity is provided as 25 GPa. With the knowledge of the length and diameter of each segment, the twist angle between the two pulleys can be computed. First, a section cut is made between pulleys B and C, and the cut cross-section is analyzed using a free-body diagram. Given that the...
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Related Experiment Video

Updated: Sep 10, 2025

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A Magnetically Transformable Twisting Millirobot for Cargo Delivery at Low Reynolds Number.

Moonkwang Jeong1,2, Jiyuan Tian2, Meng Zhang2

  • 1Cyber Valley group - Biomedical Microsystems Institute of Physical Chemistry University of Stuttgart Pfaffenwaldring 55 70569 Stuttgart Germany.

Advanced Intelligent Systems (Weinheim an Der Bergstrasse, Germany)
|August 25, 2025
PubMed
Summary

This study introduces TwistBot, a flexible millirobot that transforms into a helical shape using magnetic fields for propulsion in fluids. This innovation simplifies the fabrication of micro-robots and enables targeted cargo delivery.

Keywords:
cargo deliveryflexible bodyhelical propellermagnetic actuationmagnetic transformationsoft miniature robots

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Area of Science:

  • Robotics
  • Biomimetics
  • Materials Science

Background:

  • Bacteria flagella inspire helical micro-robots for fluid propulsion at low Reynolds numbers.
  • Fabricating rigid helical microstructures typically requires complex 3D micro-/nanofabrication techniques.
  • Current methods face challenges in producing 3D helical structures without specialized machinery.

Purpose of the Study:

  • To introduce a novel magnetically transformable millirobot, TwistBot, with a flexible body.
  • To enable propulsion in viscous fluids through shape transformation from a flat ribbon to a helical form.
  • To demonstrate a simplified fabrication approach for helical micro-robots.

Main Methods:

  • Developing a flexible millirobot (TwistBot) capable of shape transformation.
  • Applying an external magnetic field to induce twisting and helical formation.
  • Utilizing numerical simulation to model the robot's twisting behavior.
  • Optimizing the robot's geometry to maximize the twist angle.

Main Results:

  • TwistBot successfully transforms from a flat ribbon to a helical shape under a magnetic field.
  • The helical transformation enables propulsion in viscous fluids.
  • Numerical simulations and geometric optimization were used to enhance the twist angle.
  • The robot demonstrated capability for navigating narrow lumens and delivering cargo.

Conclusions:

  • The TwistBot offers a new, simplified method for fabricating transformable micro-robots.
  • Flexible helical robots can be propelled and utilized for targeted cargo delivery.
  • This concept opens avenues for designing soft, transformable minirobots for biomedical and other applications.