Bistable structures, structures with two distinct equilibrium states achieved via buckling-like deformations, are seen throughout engineering applications in shape-morphing and energyharvesting systems. Typically actuated by mechanically induced snap-through buckling, sinusoidal arches, a unique geometry, can induce bistability when fixed or pinned. However, environmental actuation via heat and humidity has yet to be explored in the literature. While existing studies focus on designing and evaluating mechanically actuated small-scale bistable arch structures, this study focuses on designing and fabricating a large-scale bistable sinusoidal arch with structural programmability through a curling property in the compliant base, that possesses applications of environmental actuation through an effective fabrication method for structural uniformity and zero initial structural frustration. Two hygroscopic materials: balsa wood and white ash wood were explored for bending. Though only mechanical actuation was tested, the material selection suggests potential for environmental actuation, paving the way for environmentally triggered autonomous actuation. The fabrication procedure required a steaming vessel and sinusoidal mold to form the arch-like component. After testing, white ash wood proved superior due to its resistance to flexural failure. The structure was tested twice, with design adjustments made and tested via numerical and experimental simulations after the first trial revealed excessive stress concentrations in the base. A final design was proposed and demonstrated bistability, though the curling action in the base was minimal.

References

• Y. Jiang et al., “Ultra-tunable bistable structures for universal robotic applications,” Cell reports physical science, vol. 4, no. 5, pp. 101365–101365, May 2023, doi: https://doi.org/10.1016/j.xcrp.2023.101365.
• Y. Chi, Y. Li, Y. Zhao, Y. Hong, Y. Tang, and J. Yin, “Bistable and Multistable Actuators for Soft Robots: Structures, Materials, and Functionalities,” Advanced Materials, vol. 34, no. 19, p. 2110384, Mar. 2022, doi: https://doi.org/10.1002/adma.202110384.
• D. Pan, H. Yang, C. Huang, and Z. Wu, “Analysis of snap-through behavior of bistable buckled beam under end-moment static actuation,” International Journal of Non-linear Mechanics, vol. 142, no. 103937, pp. 103937–103937, Jun. 2022, doi: https://doi.org/10.1016/j.ijnonlinmec.2022.103937.
• A. Rahman, S. Ferracin, S. Tank, and P. Celli, “Structural morphing surfaces from snapthrough building blocks (Modeling snap-through mechanics with DER),” in Origami/ Kirigami Inspired Structures and Metamaterials, Jun. 2023.
• P. M. Reis, “A Perspective on the Revival of Structural (In)Stability With Novel Opportunities for Function: From Buckliphobia to Buckliphilia,” Journal of Applied Mechanics, vol. 82, no. 11, Nov. 2015, doi: https://doi.org/10.1115/1.4031456.
• Y. Cao, M. Derakhshani, Y. Fang, G. Huang, and C. Cao, “Bistable Structures for Advanced Functional Systems,” Advanced Functional Materials, vol. 31, no. 45, p. 2106231, Aug. 2021, doi: https://doi.org/10.1002/adfm.202106231.
• T.-W. Liu, J.-B. Bai, H.-T. Xi, and N. Fantuzzi, “A curved bistable composite slit tube for deployable membrane structures,” Composites Communications, vol. 41, pp. 101648– 101648, Aug. 2023, doi: https://doi.org/10.1016/j.coco.2023.101648.
• E. Vazquez, Zoubeida Ounaies, E. Iatesta, and J. Duarte, “Magnetic actuation of bistable flaps for kinetic building shades,” Construction and Building Materials, vol. 392, pp. 132028–132028, Aug. 2023, doi: https://doi.org/10.1016/j.conbuildmat.2023.132028.
• C. J. García-Mora and J. Sánchez-Sánchez, “Geometric strategies to design a bistable deployable structure with straight scissors using stiff and flexible rods,” International Journal of Solids and Structures, vol. 238, p. 111381, Mar. 2022, doi: https://doi.org/10.1016/j.ijsolstr.2021.111381.
• L. Annink, O. Silier, C. Daraio, and P. Celli, “Frustrated metamaterials as pop-up dome structures.”
• S. Palathingal and G. K. Ananthasuresh, “Design of bistable arches by determining critical points in the force-displacement characteristic,” Mechanism and Machine Theory, vol. 117, pp. 175–188, Nov. 2017, doi: https://doi.org/10.1016/j.mechmachtheory.2017.07.009.
• Y. Gerson, S. Krylov, B. Ilic, and D. Schreiber, “Design considerations of a largedisplacement multistable micro actuator with serially connected bistable elements,” Finite Elements in Analysis and Design, vol. 49, no. 1, pp. 58–69, Feb. 2012, doi: https://doi.org/10.1016/j.finel.2011.08.021.
• D. Melancon, B. Gorissen, C. J. García-Mora, C. Hoberman, and K. Bertoldi, “Multistable inflatable origami structures at the metre scale,” Nature, vol. 592, no. 7855, pp. 545–550, Apr. 2021, doi: https://doi.org/10.1038/s41586-021-03407-4.
• R. Addo-Akoto and J.-H. Han, “Bidirectional actuation of buckled bistable beam using twisted string actuator,” Journal of Intelligent Material Systems and Structures, vol. 30, no. 4, pp. 506–516, Dec. 2018, doi: https://doi.org/10.1177/1045389x18817830.
• Matteo Pelliciari, Federico Oyedeji Falope, L. Lanzoni, and Angelo Marcello Tarantino, “Theoretical and experimental analysis of the von Mises truss subjected to a horizontal load using a new hyperelastic model with hardening,” European Journal of Mechanics A-solids, vol. 97, pp. 104825–104825, Jan. 2023, doi: https://doi.org/10.1016/j.euromechsol.2022.104825.
• P. Rothemund et al., “A soft, bistable valve for autonomous control of soft actuators,” Science Robotics, vol. 3, no. 16, p. eaar7986, Mar. 2018, doi: https://doi.org/10.1126/scirobotics.aar7986.
• T. Gomm, L. Howell, and R. Selfridge, “In-Plane Linear-Displacement Bistable Microrelay,” Faculty Publications, vol. 12, no. 22, May 2002, Accessed: Oct. 01, 2023. [Online]. Available: http://hdl.lib.byu.edu/1877/1153
• S.-W. Huang, Fang Yue Lin, and Y. Yang, “A novel single-actuator bistable microdevice with a moment-driven mechanism,” Sensors and Actuators A-physical, vol. 310, pp. 111934–111934, Aug. 2020, doi: https://doi.org/10.1016/j.sna.2020.111934.
• B. Charlot, W. Sun, K. Yamashita, H. Fujita, and H. Toshiyoshi, “Bistable nanowire for micromechanical memory,” Journal of Micromechanics and Microengineering, vol. 18, no. 4, p. 045005, Feb. 2008, doi: https://doi.org/10.1088/0960-1317/18/4/045005.
• S. Palathingal and G. K. Ananthasuresh, “A bilateral relationship between stable profiles of pinned–pinned bistable shallow arches,” International Journal of Solids and Structures, vol. 143, pp. 183–193, Jun. 2018, doi: https://doi.org/10.1016/j.ijsolstr.2018.03.006. • W. Yan, Y. Yu, and A. Mehta, “Analytical modeling for rapid design of bistable buckled beams,” Theoretical and Applied Mechanics Letters, vol. 9, no. 4, pp. 264–272, Jul. 2019, doi: https://doi.org/10.1016/j.taml.2019.04.006.
• J. P. Udani and A. F. Arrieta, “Programmable mechanical metastructures from locally bistable domes,” Extreme Mechanics Letters, p. 101081, Nov. 2020, doi: https://doi.org/10.1016/j.eml.2020.101081.
• Y. Li, M. Li, X. Liu, and F. Dai, “Snap-through load improvement of bistable composite shell with initial curvature by an adjustive angle,” Composites Communications, vol. 32, pp. 101190–101190, Jun. 2022, doi: https://doi.org/10.1016/j.coco.2022.101190.
• M.-L. Dano and M. W. Hyer, “Thermally-induced deformation behavior of unsymmetric laminates,” International Journal of Solids and Structures, vol. 35, no. 17, pp. 2101–2120, Jun. 1998, doi: https://doi.org/10.1016/s0020-7683(97)00167-4.
• T. Chen, J. Panetta, M. Schnaubelt, and M. Pauly, “Bistable auxetic surface structures,” ACM Transactions on Graphics, vol. 40, no. 4, pp. 1–9, Aug. 2021, doi: https://doi.org/10.1145/3450626.3459940.
• “Wood Steam Bending Q&A - Steamed Studio,” steamedstudio.co.uk, Jul. 13, 2022. https://steamedstudio.co.uk/homepage/wood-steam-bending-qa/#:~:text=How%20 long%20do%20you%20steam (accessed Aug. 28, 2023).
• “MatWeb - The Online Materials Information Resource - American Balsa Wood,” www.matweb.com. https://www.matweb.com/search/datasheet_print.aspx?matguid=81c269f50f424573a4f9978cfcb41bc8
• C. A. Senalik and B. Farber, “Mechanical Properties of Wood Chapter 5,” Forest Products Labratory, Mar. 2021. Accessed: Sep. 13, 2023. [Online]. Available: https://www.fpl.fs.usda.gov/documnts/fplgtr/fplgtr282/chapter_05_fpl_gtr282.pdf
• J. Galos, R. Das, M. P. Sutcliffe, and A. P. Mouritz, “Review of balsa core sandwich composite structures,” Materials & Design, vol. 221, p. 111013, Sep. 2022, doi: https://doi.org/10.1016/j.matdes.2022.111013.
• “MatWeb - The Online Materials Information Resource - American White Ash Wood,” www.matweb.com. https://www.matweb.com/search/datasheet.aspx?matguid=c22a32733858470aa9248bfc479d9f60&ckck=1 (accessed Oct. 02, 2023).