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Meta-Ori: monolithic meta-origami for nonlinear inflatable soft actuators

Hugo de Souza Oliveira, Xin Li, Johannes Frey, Edoardo Milana

TL;DR

Meta-Ori addresses the design and fabrication bottlenecks of nonlinear soft inflatables by integrating a snapping metashell with a Kresling origami inflatable into a single, monolithic, 3D-printed part. A Grasshopper-based design tool enables interactive parametric control of origami geometry and metashell properties, while experiments reveal a highly nonlinear, bistable pressure-volume response dominated by the metashell and transmitted through the origami. The work demonstrates significant elongation (up to 43%) and programmable actuation sequencing in a bi-segment device, achievable with relatively low pressure (~150 mbar) thanks to the foldable origami transmitter. By providing open access to the Grasshopper code and a fully integrated fabrication approach, Meta-Ori offers a scalable route to complex, programmable soft robotic actuation without manual assembly.

Abstract

The nonlinear mechanical response of soft materials and slender structures is purposefully harnessed to program functions by design in soft robotic actuators, such as sequencing, amplified response, fast energy release, etc. However, typical designs of nonlinear actuators - e.g. balloons, inverted membranes, springs - have limited design parameters space and complex fabrication processes, hindering the achievement of more elaborated functions. Mechanical metamaterials, on the other hand, have very large design parameter spaces, which allow fine-tuning of nonlinear behaviours. In this work, we present a novel approach to fabricate nonlinear inflatables based on metamaterials and origami (Meta-Ori) as monolithic parts that can be fully 3D printed via Fused Deposition Modeling (FDM) using thermoplastic polyurethane (TPU) commercial filaments. Our design consists of a metamaterial shell with cylindrical topology and nonlinear mechanical response combined with a Kresling origami inflatable acting as a pneumatic transmitter. We develop and release a design tool in the visual programming language Grasshopper to interactively design our Meta-Ori. We characterize the mechanical response of the metashell and the origami, and the nonlinear pressure-volume curve of the Meta-Ori inflatable and, lastly, we demonstrate the actuation sequencing of a bi-segment monolithic Meta-Ori soft actuator.

Meta-Ori: monolithic meta-origami for nonlinear inflatable soft actuators

TL;DR

Meta-Ori addresses the design and fabrication bottlenecks of nonlinear soft inflatables by integrating a snapping metashell with a Kresling origami inflatable into a single, monolithic, 3D-printed part. A Grasshopper-based design tool enables interactive parametric control of origami geometry and metashell properties, while experiments reveal a highly nonlinear, bistable pressure-volume response dominated by the metashell and transmitted through the origami. The work demonstrates significant elongation (up to 43%) and programmable actuation sequencing in a bi-segment device, achievable with relatively low pressure (~150 mbar) thanks to the foldable origami transmitter. By providing open access to the Grasshopper code and a fully integrated fabrication approach, Meta-Ori offers a scalable route to complex, programmable soft robotic actuation without manual assembly.

Abstract

The nonlinear mechanical response of soft materials and slender structures is purposefully harnessed to program functions by design in soft robotic actuators, such as sequencing, amplified response, fast energy release, etc. However, typical designs of nonlinear actuators - e.g. balloons, inverted membranes, springs - have limited design parameters space and complex fabrication processes, hindering the achievement of more elaborated functions. Mechanical metamaterials, on the other hand, have very large design parameter spaces, which allow fine-tuning of nonlinear behaviours. In this work, we present a novel approach to fabricate nonlinear inflatables based on metamaterials and origami (Meta-Ori) as monolithic parts that can be fully 3D printed via Fused Deposition Modeling (FDM) using thermoplastic polyurethane (TPU) commercial filaments. Our design consists of a metamaterial shell with cylindrical topology and nonlinear mechanical response combined with a Kresling origami inflatable acting as a pneumatic transmitter. We develop and release a design tool in the visual programming language Grasshopper to interactively design our Meta-Ori. We characterize the mechanical response of the metashell and the origami, and the nonlinear pressure-volume curve of the Meta-Ori inflatable and, lastly, we demonstrate the actuation sequencing of a bi-segment monolithic Meta-Ori soft actuator.

Paper Structure

This paper contains 14 sections, 8 figures.

Table of Contents

  1. Introduction
  2. Design & Fabrication
  3. Grasshopper visual code for origami inflatable design
  4. Metashell design
  5. Integration of the metashell with the origami inflatable
  6. Fabrication process
  7. Experimental setup
  8. Mechanical test
  9. Pressure-volume test
  10. Results & Discussion
  11. Mechanical characterization
  12. Pressure-Volume curves
  13. Actuation sequencing
  14. Conclusions

Figures (8)

  • Figure 1: Meta-Ori bistable inflatable actuator in fully open and closed configurations.
  • Figure 2: Sequential steps to generate the Kresling origami structure implemented in the Grasshopper visual code.
  • Figure 3: Geometric definition of the metamaterial: a) Sketch and dimensions of the bistable structure with representative construction; b) Metashell in open and closed configurations.
  • Figure 4: Description of the integration process to generate the Meta-Ori monolithic structure. The Kresling origami is placed in the middle of the metashell and sealed between two lids.
  • Figure 5: Mechanical testing of the two separated structures: a) Metashell. b) Kresling origami.
  • ...and 3 more figures