From PhysOrg:

Researchers in Taiwan report development of a new type of “molecular brake” that could provide on-demand stopping power for futuristic nanomachines. The brake, thousands of times smaller than the width of a human hair, is powered by light and is the first capable of working at room temperature, the researchers say. Their study is scheduled for the June 5 issue of ACS’ Organic Letters.

In the new study, Jye-Shane Yang and colleagues point out that the ability to control specific motions of small molecules or larger molecular structures is essential for the development of nanomachines. Some of these machines may find use in delivering drugs or performing surgery deep inside the human body.

Although scientists have already built molecular motors, wheels, and gears for powering nanomachines, the development of a practical braking system remains a challenge, the researchers say.

Yang’s group assembled a prototype molecular brake that resembles a tiny four-bladed wheel and contains light-sensitive molecules. The paddle-like structure spins freely when a nanomachine is in motion.

In laboratory studies, the scientists showed that exposing the structure to light changes its shape so that “blades” stop spinning, putting on the brakes. The braking power can be turned off by altering the wavelength of light exposure, they add.

Source: American Chemical Society

Since late last year, and especially earlier this year, it’s become typical to cast certain present-day advances in nanotechnology as building blocks for the development of advanced molecular machines for nanofabrication.

More scientists are starting to warm up to the possibility of molecular manufacturing. Does that mean that MM is imminently inevitable, like individuals such as Ray Kurzweil and organizations such as the Center for Responsible Nanotechnology seem to be arguing? Actually, no. There could be unforeseen barriers that push it back decades. I think that a lot of the analysis of Kurzweil/CRN is based on the idea that at some point in the near future, the powers that be will “realize” the power of MM and invest billions of dollars in it. If studies in the millions of dollars range fail to provide serious results, then the “domino effect” of successful studies and designs will not get going, and MM will not materialize.

However, if the domino effect does get going (assign whatever probability to it that you like), then we could have an almost entirely automated economy when it concludes. MM, if it’s feasible at all, would trigger an Industrial Revolution more extreme than all past industrial progress combined, shoved into the space of less than a decade. It would give us construction materials 100 times stronger, motors and generators over a million times smaller and 10 times more efficient. Any “in between” isn’t really feasible — either we gain the ability to construct human-sized products atom by atom using molecular machinery, or we don’t. If we don’t, then we might use some sort of micromachine-based “fab lab” for decentralized, customized fabrication two decades from now, which would provide superior products to today’s, but nothing like the “magical” improvement gains offered by molecular manufacturing. If we do, then the entire economic, social and political landscape could be disrupted like porcelain figurines in a paint mixer.