Chapter 2: Building Blocks
38 - Strutting (Part Two)
As Ingber explains it, the constant internal push and pull of tensegrity is a factor at each level, holding together everything from molecules through cells to bones and muscles and tendons. In his view it’s the only mechanism that explains how, every time you move your arm, “your skin stretches, your extracellular matrix extends, your cells distort, and the interconnective molecules that form the internal framework of the cell feel a pull.”
Molecular Geodesics, Inc., or MGI, was founded in 1996 to apply those principles in the design of custom-made materials. The company also developed software for use in evolving materials based on those principles—for instance, in the creation of filtering devices. If one wants a material that allows a lot of air through it—say, 95 percent porosity—Ingber says, they could “just tell the computer to build it.” Typical instructions might call for varying a tetrahedral shape, as well as the width and the height of each strut. “In three minutes the computer goes through three million possibilities,” he says. “Of those, three hundred thousand fit the shape, and maybe twenty-one of them have 95 percent porosity.” Then comes the interesting part, he adds. “Some of them have huge, thick struts and are almost all air. Some have tiny little struts but thousands of them. Each model would have the same porosity, but with very different surface areas, different mechanical properties.”
MGI received a DARPA contract to develop those concepts into synthetic biomimetic materials for use in protective masks, battle dress, and artificial bioskins (high-porosity layers designed to hold chemicals or enzymes that could neutralize any biological warfare agent passing through them). MGI’s plan was to develop them with a rapid prototyper. That is a kind of 3-D lithographer in which, for instance, a liquid polymer is infinitesimally solidified—microscopic layer by microscopic layer—using a precision laser beam guided by a computer model.
Rapid prototyping allows quick construction of intricate three-dimensional models, but the MGI team ran up against an engineering barrier. They couldn’t tweak the existing technology to produce structures at a fine enough scale for their aims. That was the end of their work for DARPA. But prior to that the company had also been working on orthopedic applications, on the creation and manufacture of “porous scaffolds that mimic the precise microstructure of living materials.” The aim there was to design components that would “induce new tissue growth and regeneration” and that were fully biocompatible and resorbable. One early brochure even showed a mock photo of an off-the-shelf, complete “Left Leg Kit (Male).”
Under a new name, Tensegra, Ingber’s team successfully developed a synthetic vertebral disc. But on the eve of a crucial fund-raising effort, the terrorist attacks of September 11, 2001, put most new venture capital activity on hold. A short time later, the company closed its doors. Ingber remains in his other positions, and as a consultant to industry. He also continues to publish research on tensegrity and the function of the cytoskeleton, including his theory that through it, forces outside the cell can affect the nuclear DNA by mechanical means.
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