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. 2023 Sep 26;8(6):455.
doi: 10.3390/biomimetics8060455.

A Bio-Inspired Arched Foot with Individual Toe Joints and Plantar Fascia

Stuart Burgess  1 , Alex Beeston  1 , Joshua Carr  1 , Kallia Siempou  1 , Maya Simmonds  1 , Yasmin Zanker  1
Affiliations

A Bio-Inspired Arched Foot with Individual Toe Joints and Plantar Fascia

Stuart Burgess et al. Biomimetics (Basel). .

Abstract

This paper presents the design and testing of an arched foot with several biomimetic features, including five individual MTP (toe) joints, four individual midfoot joints, and plantar fascia. The creation of a triple-arched foot represents a step further in bio-inspired design compared to other published designs. The arched structure creates flexibility that is similar to human feet with a vertical deflection of up to 12 mm. The individual toe joints enable abduction-adduction in the forefoot and therefore a natural pronation motion. Adult female bone data was obtained and converted into a CAD model to accurately identify the location of bones, joints, and arches. An analytical model is presented that gives the relationship between the vertical stiffness and horizontal stiffness of the longitudinal arches and therefore allows the optimization of stiffness elements. Experimental tests have demonstrated a vertical arch stiffness of 76 N/mm which is similar to adult human feet. The range of movement of the foot is similar to human feet with the following values: dorsi-plantarflexion (28°/37°), inversion-eversion (30°/15°), and abduction-adduction (30°/39°). Tests have also demonstrated a three-point contact with the ground that is similar to human feet.

Keywords: MTP joints; arch stiffness; foot prosthetic; plantarflexion; robotic foot; windlass mechanism.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Bones of the human foot.
Figure 2
Figure 2
Three arches of the human foot.
Figure 3
Figure 3
Three point-contact from three arches in the foot.
Figure 4
Figure 4
Foot axes of rotation (pronation axis from [33]).
Figure 5
Figure 5
An adult female foot was used to determine key geometric points. (a) Three-dimensional printed bones (b) Geometry of middle toe.
Figure 6
Figure 6
Bio-inspired foot design. (a) Prototype (no plantar fascia). (b) Schematic side view. (c) Section showing nylon cable (d) Plan view of foot.
Figure 7
Figure 7
Model of each metatarsal arch as a mechanism.
Figure 8
Figure 8
Stiffness test on the bio-inspired foot.
Figure 9
Figure 9
Vertical stiffness of the arch at the midfoot joint.
Figure 10
Figure 10
Extreme positions of the bio-inspired foot (all right foot).
Figure 11
Figure 11
Contact patch of the bio-inspired foot and human foot (right foot). (a) Bioinspired foot (b) Human foot.
Figure 12
Figure 12
Profiled heel to initiate natural CoP pathway.
Figure 13
Figure 13
Bio-inspired foot during the gait cycle.
See this image and copyright information in PMC

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