Biotensegrity

Original Editor - Vidya Acharya

Top Contributors - Vidya Acharya and Khloud Shreif  

Tensegrity

Tensegrities are self-equilibrium structures composed of discrete compression struts and continuous tension cables. Tensegrity structure refers to any physical structure that combines the features of tension and stability in a specific manner. The structure is stable due to the way the entire structure distributes and manages balances. The structures maintain their integrity because of the balance between the woven tensile force continual through the structure. Bicycle wheels are examples of tensegrity structures, with spokes carrying tension and the rim carrying compression.

Richard Buckminster Fuller, David Georges Emmerich, and Kenneth D. Snelson have been recognised as the inventors of tensegrity. Multiple claims exist regarding the originator of the term. Even though all three have claimed to be the first inventor, Emmerich has reported that the first proto-tensegrity system, "Gleichgewichtkonstruktion," was created by Karl Ioganson in 1920.

Literature points out the term ‘tensegrity’ was first coined by the architect Buckminster Fuller; the term combines the words ‘tension’ and ‘integrity’. However, his student, American sculptor Kenneth Duane Snelson is said to have constructed first self-stabilizing tensegrity structure using a combination of flexible and rigid components assembled using the concept of 'tensegrity'. Snelson used the descriptive term 'floating compression'. According to Kenneth Snelson, tensegrity describes a closed structural system composed of a set of three or more elongate compression struts within a network of tension tendons. The compression elements (struts) do not touch, and instead are suspended by connections to a continuous series of tension elements (cables). The combined parts support each other in such a way that the struts do not touch one another, but press outwardly against nodal points in the tension network to form a firm, triangulated, prestressed, tension and compression unit.

They way in which the tensegrity model differ from other rigid structures is that its structures are not held or connected by compressions as seen in a wall where bricks are stacked on one another. Instead, they are connected through a global network of tension. The rigid elements, such as struts or beams, are held together by a network of tensioned elements of structures like cables, strings or even membranes. These rigid struts do not touch each other instead they seem to float in a continuum of tensile forces. This arrangement gives shape and stability to the structure.

Properties or the behaviour of such a structure when subjected to external forces are as follows:

• The forces transmit through the entire structure, and affect every single component
• The individual components realign themselves immediately when force is exerted on any particular component
• The nature of force transmission in a reversible without undergoing any damage.
• So, if we pull a string in the model or break a strut, the whole arrangement reorients itself to accommodate the change
• This interconnectedness of the structural element distributes the tensile forces across the entire tensegrity structure again implying that a force applied in a specific area may cause a reaction in the whole structure

Biotensegrity

We see tensegrity patterns in all living structures: plants and animals. In the human body, large molecules self-assemble into cellular components known as organelles, which self-assemble into cells, which self-assemble into tissues, which self-assemble into organs. The result is a body organized hierarchically as tiers of systems within systems. Applying the principles of tensegrity at the cellular level helps us to understand the way living creatures form and function. Mechanical stimuli is important in organ development, tissue homeostasis, as well as disease process. The cells not only sense biochemical cues but also physical factors such as force, geometry and matrix elasticity, and that is essential for cell and tissue functions, morphology, regeneration, physiology and pathology.

Mechano-transduction

Mechanobiology is the study of the essential roles that these physical factors play via the process of mechanotransduction.

At cellular level, mechano-transduction is a process in which cells sense physical forces and transduce these mechanical cues into changes in intracellular biochemistry and gene expression. At the tissue level, multicellular structures are held together by cell adhesions. Forces acting upon these adhesions play an integral role in dynamically re-shaping multicellular structures. In a multicellular structure, mechanical forces are transduced in a variety of ways, including mechanosensing through a compliant substratum, cytoskeletal 'tug-of-war' between cell-matrix and cell-cell adhesions, cortical contractility that contributes to line tension, stresses caused by cell proliferation, and forces mediating collective migration. The cells use tensegrity architecture to structure themselves at the molecular level, and that depends on tensile prestress for its mechanical stability enables cells to sense and respond to mechanical signals.

Additional Reading

• Gough, M. (1998). In the Laboratory of Constructivism: Karl Ioganson’s Cold Structures. October, 84, 90. doi:10.2307/779210

• Pflüger C. The meaning of tensegrity principles for osteopathic medicine. Pflüger; 2008 Oct