Understanding Bio-mimicry
Table of Contents
Can Engineering Principles be seen in Nature (Bio-Mimicry)
It can be seen that complex human problems have been solved by using ideas from nature, or imitating systems and elements in nature. This is defined as bio-mimicry and biomimetic. Examples of this are Velcro, the Shinkansen bullet train, candy-coated vaccines, firefly light bulbs and many more including tensegrity structures. Initially, it may not seem that the concept of tensegrity is from nature at all, however, the human body is a prime example of tensegrity.
The skeletal structure of the body is a connection of bones through joints; these joints can be hinged joints, fibrous joints or ball and socket joints. The hinged joints allow rotation and free movement, like the elbows and knees, also, the ball and joints, have synovial fluid in them, this is so the joints do not deteriorate over one’s life due to friction. This shows bones are not in direct contact with other at the joints, there are ligaments which hold the bones together. The ligaments act to keep the structure stable as they are a fibrous connective tissue, which can be best described as a very strong rubber band by Linda J (2014).
Cytoskeleton
Regarding human biology, the building blocks of humans are cells which, come together to produce tissues, muscles and organs. Ingber et al (1998) conducted a study to clarify whether cytoskeletal tension is a major determinant of cell deformability in adherent endothelium. They analysed endothelial cells by cutting them or dethatching them from their basal surface using a micro needle. After cutting or detachment, the cells retracted, however the retraction was prevented manually, and the cytoskeleton actin lattice was analysed.
It was found that the cytoskeleton actin lattice had pre-tensioning forces acting within its structure as well acting as an elastic material. Their results showed that cytoskeleton pre-tensioning force is a major component in the cell deformability and shape in a cell. Pre-tensioning is a major constituent in the principles of tensegrity in forming the shape of the structure, as the amount of pre-stress determines the overall shape in a tensegrity structure as well as a cell.
Furthermore Ingber (1993) demonstrates that the cytoskeleton of a cell can be described as a tensegrity structure. The cytoskeleton of the eukaryotic cells is divided in three major classes of filamentous biopolymers.
These are actin-containing micro-filaments, tubulin-containing microtubules and intermediate filaments, where the cytoskeleton filaments can resist large changes in its structural shape due to its ability to resist mechanical loads.
It is further stated that the “actin microfilament lattice behaves as if it depends on tensional integrity” as cited by Ingber (1993), this is because when a cell exerts centripetal tension on localized focal adhesions, isolated regions of underlying compression resistant extra-cellular matrix, resist the continuous tension produced by the cytoskeleton locally.
It is further regarded that the microtubules act as compression-resistant struts and that the intermediate filaments acts as a tensile stiffener. However, although this evidence points to cells as having a tensegrity design, it is still a theory that has not been verified as there is no way to replicate an actual living creature that is supported by a system of rigid bones interconnected by a series of tensile muscles that can produce movement.
Currently we are only confined to physical models consisting of wood and strings. Despite this, nature uses triangulation and tensional integration for its structural stability. (Ingber, 1993)
Elbow as a Tensegrity Structure
It can be taken into consideration that the human elbow acts as a tensegrity structure for various reasons; it is commonly described as a uniaxial joint that allows movement in a single plane that provides a pivot for the forearm rotation. It allows a rotation of 145 degrees of the upper limb and a 150 degree rotation of the forearm, which enables the hand to carry out its desired functions. (Scarr, 2011).
The elbow can be broken up into four components, its joints, ligaments, muscles and nerves. Each of these components has a role into how it transforms the elbow into a tensegrity structure.
The elbow has a synovial joint and is a hinge joint which allows movement. It is comprised of the capitulum, tochlear notch of the ulna, head of the radius and the trochlea of the humerus that is enclosed by a fibrous capsule. There is no direct attachment of the joint capsule to the radius; otherwise, movement of the elbow will become severely restricted. (Nigel, et al., 2006)
The elbow can be broken up into four components, its joints, ligaments, muscles and nerves. Each of these components has a role into how it transforms the elbow into a tensegrity structure.
The three bones in the elbow joint act as rigid bodies connected by a joint and undergo compression, connected by a “sea of tension”; the tendons are attached to the dozens of flexor and extensor muscle groups, the muscles themselves are pre-tensioned for when there is muscular movement in the fascia and muscle cells. This enables the elbow joint to remain stable and in equilibrium and is a pre-requisite condition for any tensegrity structure.
The elbow joint can be defined as a class 3 tensegrity structures as stated by Skelton & Oliverira (2009) because there are 3 rigid bodies which give the impression of floating, and it remains stable due to the muscles and tendons, which is another condition of a tensegrity structure. It was found that muscles connecting to the elbow joint through the fascia were in constant pre-tension as cited by Scarr (2011).
This is one of the key components of a tensegrity structure, if not all, and further suggests that the elbow should not be considered in separate parts where bones and muscles are connected together, but rather as a tensegrity system.
The elbow can be broken up into four components, its joints, ligaments, muscles and nerves. Each of these components has a role into how it transforms the elbow into a tensegrity structure.
References
- Linda J, V., 2014. nlm.nih. [Online]
Available at: http://www.nlm.nih.gov/medlineplus/ency/imagepages/19089.htm
[Accessed 01 December 2014]. Ingber, D. E., 1993. Cellular tensegrity: defining new rules of biological design that govern the cytoskeleton. Journal of cell science, Volume 104, pp. 613-627.
Scarr, G., 2011. A consideration of the elbow as a tensegrity structure. International Journal of Osteopathic Medicine, Issue 15, pp. 53-65.
Skelton, R. E. & Oliverira, M. C. d., 2009. Tensegrity Systems. London: Springer.