WP4: iDesign – Simulation Methods

Key Question:

How can we develop an optimized design of an outer shaft of a lower limb prosthesis with high strength and stiffness but with low weight?

Work Package Summary

WP4 deals with the design optimization of the outer shaft of a lower limb prosthesis based on lightweight lattice structures using biomimetic principles inspired by the mechanics of the wing of dragonflies.

The main goals of iNclude

Simulation Methods

WP4 deals with the development of a design methodology for high-stiffness, lightweight parts, demonstrated on an outer shaft of a prosthesis based on dragonfly structures. Dragonfly wings represent remarkable examples of a balance between load‐bearing and durability. This balance is achieved through a compromise between stiffness and flexibility. Dragonfly wings are stiff enough to withstand aerodynamic loads and flexible enough to deform without failure. Joint‐like structures play a key role in this regard. Due to their “weaker” structure or material, the joints are often more flexible than other wing components.

Figure: Joint structures in the dragonfly wing [1]

[1] Figure modified according to Attribution 4.0 International (CC BY 4.0)  – based on the original derived from: Khaheshi, A., Gorb, S., Rajabi, H., Triple Stiffness: A Bioinspired Strategy to Combine Load‐Bearing, Durability, and Impact‐Resistance. Adv. Sci. 2021, 2004338. https://doi.org/10.1002/advs.202004338.

As can be seen in Fig. 1, the different joint-like structures in the wing of the dragonfly have a different geometry which leads to different mechanical behavior. There are flexible joints that allow high deformability, mechanical stoppers that lead to a fixed lattice structure, and buckling zones in which the joint is rotatably supported along a lattice truss structure. Fig.1 also shows that the overall stability of the wing is achieved by connecting the lattice bars with a membrane-like layer. By linking the different components in the dragonfly, an adaptive structure is achieved that can support high loads, while at the same time being flexible enough to absorb sudden load shocks without damage, and all gather in a highly lightweight construction.