Todd Anderson asked a good question in our blog comments:
"Will
shielding be needed for background radiation in the device and is there
any know element that can protect the inner workings of the MM device?
Or will another kind of shielding be needed i.e. magnetic or a new as
yet unknown one?"
I don't know of any way to shield against all background radiation. Even alpha particles, which can be stopped by "a piece of paper" - a piece of paper is small compared to a tabletop device, but large compared to, say, a medical nanodevice. And there are other kinds of radiation that are more penetrating.
So there will definitely be some level of radiation damage. (By the way, this level of damage is many orders of magnitude larger than errors from entropy, Heisenberg uncertainty, or any of the other weird physics that skeptics like to invoke to make molecular manufacturing sound difficult.)
To deal with damage, use redundancy. If you need eight parts to work, include nine in the machine you're designing. Do that at several levels, and a machine with quadrillions of sensitive components can reliably keep working for years with something like 30-40% extra machines.
Biology, of course, uses self-repair, metabolism, and other kinds of error adaption. But they're not necessary in engineered nanomachines.
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