Bio-Tensegrity to Bio-Elastegrity: the Architecture of Life

Leftheris Pavlides

Saturday, 1 Feb, 11:30-12:00 p.m.

Artwork by Leftheris Pavlides
Video 1   Video 2   Video 3

Elastegrities are structures comprising a network of rigid and elastic members characterized by form resilience, and in this they resemble tensegrities (internal elastic forces maintain the shape’s integrity, thus the name “elastegrity”). Elastegrities exist into two families: nodal elastegrities, made with rigid struts linked at the vertices with linear elastic members; and hinge elastegrities, made with rigid solids linked with elastic hinges.

Ingber suggests that cells are not formless blobs, but instead resemble tensegrities in behavior. This new understanding presents a huge improvement over previous ideas of biological structure. In the 2003 “Tensegrity I. Cell structure and hierarchical systems biology” article, Ingber cites thirty articles where the “tensegrity principle is invoked to explain an unusually wide range of unexplained phenomena in many different biological systems and species.”

Tensegrities are a subfamily of nodal elastegrities, where struts are connected with elastic pre-stressed cables. Unlike springs the pre-stressed cables have zero resistance to compression. Ingber experimented with nodal elastegrities using springs instead of cables but did not call them elastegrities.

We will demonstrate that Ingber’s tensegrity model for biological form can be strengthened if expanded to include hinge elastegrities that oscillate with variable pressure, contracting and expanding along predictable three-dimensional trajectories between regular and semi-regular solids. We review the citations in Ingber’s article that use tensegrities to explain biological phenomena in many different biological systems and species and provide examples demonstrating improvements afforded by hinge elastegrities to modeling nature’s forms compared with nodal tensegrities such as:  1) tensegrities exist in “isometric tension” only in stasis while elastegrities maintain isometric tension as they move with chirality through space; 2) by contrast to nodal tensegrities, hinge elastegrities can contain liquids and 3) act as non-Newtonian pumps, 4) have simpler assembly through folding rigid and elastic members out of one planar material.

For example Stephen Levin, cited in Ingber’s article for his tensegral interpretation of the musculoskeletal, has pointed out that the chiral isometric movement of hinge elastegrities helps explain why the head does not “wobble on top of the spine” as it would if it was a nodal tensegrity and is consistent with the fact that muscles are attached along the length of bones rather than at the nodes provides an example of elastegrities being superior to tensegrities in modeling biological form. Additional such examples from the structure of the cytoskeleton to the structure of the skin will be presented.

 

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