Yu-Chen Yen's research works | National Taiwan University and other places

The origami fruit model inspired by S. polysperma. A Inspired by the winged fruits of S. polysperma, we make three-winged origami fruits using origami techniques for experiments. Flexible and rigid origami fruits are both made by changing the wing stiffness. For flexible samples, we reduce the wing stiffness by cutting off one layer of the original double-layered paper of the wings, leaving only one layer. For rigid samples, a 3D-printed frame is inserted into the middle of the double-layered paper wing. B Illustration of geometrical nomenclature of origami fruits. In particular, the span is labeled as l, and the folding angle is φ. When the origami fruit falls freely, it eventually descents with a terminal velocity U and rotates with an angular frequency ω = 2πf, where f is the rotational frequency

The experimental setup and deformation analysis. A Three cameras are set up to track the flight trajectories of the origami fruits, two of which are perpendicular to each other to capture the falling speed, and the third one below the origami fruit is used to analyze the rotation. B The experimental setup to capture wing deformation. One high-speed camera is set up to analyze the deformation of the origami fruit during the steady descent. C Deformation is discussed in two parts: wing-tip deformation and folding angle change. We put the film into the open-source software Tracker to measure them

Velocity and rotational frequency analyses. The left panel shows the origami fruit’s transient and steady decent processes. The right panels show a representative case of velocity analysis (top) and rotational frequency analysis (bottom). The origami fruit rotates counterclockwise when viewed from below

Comparison of the experimental results of rigid and flexible origami fruits with different folding angles φ. A The graph shows the velocity evolution (solid curves) and rotational frequency evolution (dashed curves) in the free-falling experiments of the rigid origami fruits. The solid and dashed curves represent mean values; shaded regions indicate the range of ± 1 s d. The bottom right panel shows that the upward lift force (FZ) equals the downward gravity force (FG) when the origami fruit reaches a steady state. A is the projected area of the wings. B Comparison of the experimental results of rigid (blue) and flexible (red) origami fruits with an initial folding angle of 110 degrees. C 120 degrees. D 130 degrees. E 140 degrees. The solid and dashed curves represent mean values; shaded regions indicate the range of ± 1 s d. (Color figure online)

3D trajectories of rigid (blue) and flexible (red) origami fruits with a 120° initial folding angle. Comparison of the experimental and simulation results for the rigid case (A) and the flexible case (B). Two different specimens were tested. Each repeated five times. Total 10 times for each case. C Comparison of the simulation results, superimposed with the projected trajectories on the xy plane, between the rigid and flexible cases. Note that the horizontal scales are different between (A)(B), and (C). (Color figure online)

Folding angle and wing flexibility influence the flight performance of origami winged fruits

May 2024

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Nonlinear Dynamics

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Winged fruits possess a unique flight mechanism relying on simple geometric structures rather than neuromuscular control. This study proposes an innovative approach using origami techniques to create three-winged model fruits, serving as a proxy for understanding the flight dynamics of natural winged fruits. Paper is employed to simulate inherent wing flexibility, with the option to add plastic frames for rigidity. We comprehensively investigate the free fall motion of both rigid and flexible winged fruits through experimental and numerical analyses. Velocity–time curves reveal a three-stage descent pattern—acceleration, deceleration, and steady states. The overshoot phenomenon is attributed to rapid lift increase due to leading-edge vortices attaching stably to the wings. This insight sheds light on aerodynamics governing fruit flight. Compared with rigid wings, flexible wings exhibit two key properties—slower descent and higher self-orienting capability—that facilitate a more stable and longer-distance dispersal of seeds under crosswind conditions. Our study demonstrates the potential benefits of flexible wings in natural seed distribution. This study advances our understanding of winged fruit flight dynamics, utilizing origami as a powerful tool for biomimetic investigations. The findings have broad implications, from improving aerodynamic designs to developing efficient micro air vehicles and electronic microfliers, and understanding seed dispersal evolution. Graphical abstract

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Yu-Chen Yen's research while affiliated with National Taiwan University and other places

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