A Simulation Framework for the Design and Fabrication of Functional Micro-Origami

Origami principles provide several unique advantages including self-assembly, an ability to stow and deploy structures, geometric reconfiguration, and tunable mechanical behaviors. Within the field of 2D photolithography-based microfabrication processes, origami offers transformative advancements in creating 3D systems and assemblies, making it possible to fold practical micro-scale systems such as bio-medical devices, drug delivery containers, micro-robots, and shape morphing metamaterials. While different principles can be used to create and fold micro-origami, the conception and design of these systems are often challenging because advanced, multi-physical finite element methods are needed to effectively capture the relevant real-world behaviors. To address this issue, we present a rapid simulation framework tailored for capturing these behaviors and test it on a new electro-thermal micro-origami system. The simulation framework is based on a simplified and sparsely meshed bar and hinge model that can capture the elastic large deformation behaviors in origami-inspired structures [1]. We introduce a compliant crease model that better approximates the 3D geometry of the active crease region and can simulate the global time-variant folding which is driven by local crease actuation [2]. The framework is further enhanced by a simplified contact model that can initiate and disengage contact interactions, prevents penetration of the thin sheet panels, and provides force continuity for mechanical simulation [3]. Contact within micro-origami is important for ensuring the correct folding sequence, for achieving functional capabilities such as gripping of objects, and for interacting with external surfaces such as the silicon wafer from which the micro-origami is released. We further introduce a simplified meshless approach to capture heat transfer within and from the origami-inspired systems. The behavior of thermally actuated micro-origami is highly dependent on the local heating of the actuator regions and the atmospheric cooling which varies with the folded 3D configuration. We apply the simulation framework to model the behavior of a new type of micro-origami where the folding of the active region is driven by Joule heating of a gold and polymer bilayer [4].  The interdependent geometric, thermal, and mechanical behaviors are effectively simulated for different folded systems including multi-fold origami panels and micro-grippers. While only upward folding can be achieved with this fabrication method, we show that systems that employ single-degree-of-freedom origami designs can achieve complex folded shapes such as the Miura-ori and the origami crane. We envision that this simulation framework can enable the future design and optimization of various micro-origami with functional and shape morphing capabilities.

References

[1] Filipov, E.T., Liu, K., Tachi, T., Schenk, M., and Paulino, G.H. (2017) “Bar and Hinge models for Scalable Analysis of Origami.”International Journal of Solids and Structures, Vol. 124, No. 1, pp. 26-45.

[2] Yi Zhu, Evgueni T. Filipov (2020) “A Bar and Hinge Model for Simulating Bistability in Origami Structures with Compliant Creases.” Journal of Mechanisms and Robotics. 12(2): 021110 (10 pages). (doi:https://doi.org/10.1115/1.4045955)

[3] Yi Zhu, Evgueni T. Filipov (2019) “An Efficient Numerical Approach for Simulating Contact in Origami Assemblages.” Royal Society Proceedings A. 475: 20190366 (doi:https://doi.org/10.1098/rspa.2019.0366)

[4] Yi Zhu, Mayur Birla, Kenn R. Oldham, Evgueni T. Filipov (2020) “Elastically and Plastically Foldable Electro-Thermal Micro-Origami for Controllable and Rapid Shape Morphing.” Advanced Functional Materials (Accepted)