By Andrew Nusca
Posting in Environment
Scientists have developed self-assembling, transparent nanospheres that are stiffer than steel and Kevlar. They could be used in medical implants and space tech.
Scientists have developed self-assembling, transparent nanospheres that are stiffer than steel -- and even Kevlar.
The result is the stiffest organic material ever invented, the researchers claim. In fact, only diamond probes were able to make an indentation in the biological material, Rousso said.
The value of such a material lies in strengthening composites, for as diverse applications as medical implants and a space elevator.
Yes, a space elevator.
While the researchers are quick to admit in a Chemistry World report that there's a big gap between their discovery and such uses, it's certainly another step forward in materials science.
Specifically, the spheres were made from N-tert-butoxycarbonyl (Boc)-protected diphenylalanine, which in unprotected form is the key ingredient in the beta-amyloid protein that facilitates plaques in the brain that form as a result of Alzheimer's disease.
The diameters of the highly-ordered spheres ranged from 30nm to 2um.
So how strong are these things? For comparison's sake, a 1um-diameter particle had a 275GPa Young's modulus -- a measure of stiffness -- compared to 200GPa for steel and 130GPa for Kevlar.
The difference is that the molecules' structure -- and thus stiffness -- may rely on pH. That fact could limit the environments in which the material could be used, but could also give it a "trigger" that transforms it into a smart material.
Oct 25, 2010
The sphere shape is a potential stumbling block for any tension-critical application such as a space elevator ribbon. In fact, there are a plethora of substances suitable for the COMPRESSION strengths such a structure would require (ie, the clamping strength needed to keep a good grip on the flat cable). But ANYTHING that can ONLY take a spherical shape ("self-" assembly) will prove very difficult to work with, in terms of engineering the TENSION strength needed to support the whole weighty edifice into the orbital zone, and to carry the upward weight of the required counterbalance at the "top" of the cable. In fact, I would estimate the usefulness of this development in tension applications to be near zero, unless something dramatic happens to the design (such as developing long fibers with it). I think long buckytubes are still the best bet.
When you start rigorously measuring qualities like hardness and stiffness, and reporting numbers like 275GPa, then there is no longer any such thing as "steel," but rather 2,000 different kinds of steel that vary as to the amount of carbon in them and how rapidly they were cooled from high temperatures (the same composition steel can be hard or soft depending on how rapidly it was cooled) and the presence of other constituents like nickel, chromium, boron... all kinds of things. So to tell us this stuff is "stiffer than steel" tells us nothing useful.