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Macro-Scale Electrostatic Origami Motor

Alex S. Miller, Leo McElroy, Jeffrey H. Lang

TL;DR

This work addresses the lack of macro-scale foldable rotary actuation by introducing the first collapsible origami motor powered by corona discharge. The authors design a two-cylinder Kresling-based rotor–stator, fabricate electrodes on flexPCBs, and develop an electrostatic torque model that links geometry and material properties to performance. Experimental results show a 2.5:1 deployment expansion, a top speed of 1440 rpm at −29 kV, and a maximum motor torque above 0.2 mN m with a 0.15 mN m observable output torque, demonstrating viable volumetric torque with active-component torque density around 0.04 Nm/kg. The study highlights potential applications in soft, foldable robotics and outlines clear avenues for increasing torque density, reducing folded volume, and exploring alternative electrostatic actuation topologies.

Abstract

Foldable robots have been an active area of robotics research due to their high volume-to-mass ratio, easy packability, and shape adaptability. For locomotion, previously developed foldable robots have either embedded linear actuators in, or attached non-folding rotary motors to, their structure. Further, those actuators directly embedded in the structure of the folding medium all contributed to linear or folding motion, not to continuous rotary motion. On the macro-scale there has not yet been a folding continuous rotary actuator. This paper details the development and testing of the first macro-scale origami rotary motor that can be folded flat, and then unfurled to operate. Using corona discharge for torque production, the prototype motor achieved an expansion ratio of 2.5:1, reached a top speed of 1440 rpm when driven at -29 kV, and exhibited a maximum output torque over 0.15 mN m with an active component torque density of 0.04 Nm/kg.

Macro-Scale Electrostatic Origami Motor

TL;DR

This work addresses the lack of macro-scale foldable rotary actuation by introducing the first collapsible origami motor powered by corona discharge. The authors design a two-cylinder Kresling-based rotor–stator, fabricate electrodes on flexPCBs, and develop an electrostatic torque model that links geometry and material properties to performance. Experimental results show a 2.5:1 deployment expansion, a top speed of 1440 rpm at −29 kV, and a maximum motor torque above 0.2 mN m with a 0.15 mN m observable output torque, demonstrating viable volumetric torque with active-component torque density around 0.04 Nm/kg. The study highlights potential applications in soft, foldable robotics and outlines clear avenues for increasing torque density, reducing folded volume, and exploring alternative electrostatic actuation topologies.

Abstract

Foldable robots have been an active area of robotics research due to their high volume-to-mass ratio, easy packability, and shape adaptability. For locomotion, previously developed foldable robots have either embedded linear actuators in, or attached non-folding rotary motors to, their structure. Further, those actuators directly embedded in the structure of the folding medium all contributed to linear or folding motion, not to continuous rotary motion. On the macro-scale there has not yet been a folding continuous rotary actuator. This paper details the development and testing of the first macro-scale origami rotary motor that can be folded flat, and then unfurled to operate. Using corona discharge for torque production, the prototype motor achieved an expansion ratio of 2.5:1, reached a top speed of 1440 rpm when driven at -29 kV, and exhibited a maximum output torque over 0.15 mN m with an active component torque density of 0.04 Nm/kg.
Paper Structure (7 sections, 16 equations, 13 figures, 1 table)

This paper contains 7 sections, 16 equations, 13 figures, 1 table.

Table of Contents

  1. Introduction
  2. Design
  3. Analysis
  4. Assembly
  5. Testing and Results
  6. Discussion
  7. Acknowledgments

Figures (13)

  • Figure 1: Assembled electrostatic origami motor.
  • Figure 2: Key dimensions in the mechanism unit cell design.
  • Figure 3: The flexible circuit boards for the rotor and stator are designed in JSON-PCB, an open source script-based PCB design tool especially suited to parametric designs leomcelroy_leomcelroyjson-pcb_2025mcelroy2022svg.
  • Figure 4: The (a) rotor and (b) stator printed circuit boards.
  • Figure 5: Cross section of origami motor computer rendering with components labeled. The Kresling structure was generated using a CAD script hanson_controlling_2024 and adjusted to system constraints.
  • ...and 8 more figures