X-Message-Number: 33024 Date: Wed, 3 Nov 2010 08:45:58 -0400 From: "Perry E. Metzger" <> Subject: powering nanosystems References: <> > From: Gerald Monroe <> > Date: Tue, 2 Nov 2010 04:30:49 -0500 > Subject: Re: CryoNet #33017 - #33019 > > > External magnetic fields for a power source? An unrealistic idea, IMHO... > Why not just use DC > current? Molecular manufacturing equipment will be physically tied > to a macroscopic host machine that can supply them directly with > electricity, cooling, and reactive intermediates from feedstock. > See this video for some concepts : > http://www.youtube.com/watch?v=vEYN18d7gHg&feature=player_embedded. That's not really a sufficient answer, no. That video is about a desktop nanofactory. (The video, btw, is pretty good at a high level but sadly unrealistic in some of its details -- it fairly freely chooses to depict structures that would have to be visibly made of atoms as undifferentiated bulk material for example, depicts grippers holding on to highly reactive depassivated diamond structures, and a number of other material behaviors which feel unrealistic.) We would expect a *desktop* nanofactory to be immobile (say, atop a desk.) Just as a modern machine shop can get its power from the AC lines and is an essentially immobile structure, while automobiles or aircraft made with such immobile equipment have to be able to move around, a desktop nanofactory is going to be essentially immobile, but other sorts of nanomachines (say, for example, Freitas' design studies for "respirocites" and "microbivores") will be mobile and the size of cells or smaller. I would expect most medical systems to be physically untethered in this manner. Clearly, mobile nanosystems of this type cannot get their power from externally supplied electric current. However, there is no great mystery to solve as to how they could get power, either. In Freitas' theoretical designs for machinery that operates inside the human blood stream, power comes from oxidizing glucose in specialized machinery in a small part of each machine. This is a reasonably convenient source inside the human body. Many other mechanisms are possible, with practicality depending on operating conditions as well as fundamental limitations imposed by physics. A great number of such mechanisms are considered in considerable detail in "Nanosystems", along with ways for nanomachines to communicate with macroscopic systems (surprisingly, acoustic communication turns out to be a good choice in many situations), mechanisms for the control of nanomachines, etc. This work has been extended by people like Freitas in his very detailed work "Nanomedicine" which discusses these topics and more (including problems specific to medical applications like the biocompatibility of the materials such machinery might be made from.) The field is hardly all worked out -- it is, in fact, in its infancy -- but I would suggest that if people are interested in such topics they would do well to read the existing literature. (The literature is also a lot better than artist's conceptions in the form of videos.) I would also suggest that people should be a aware of the environment that leads to periodic breathless news stories about various scientific papers, such as the one that triggered this discussion. University PR departments often hype things without regard to their actual significance, and reporters are frequently ill educated in science. Researchers frequently play along to some extent because of the way the funding game is played. Taking popular press stories about new developments with a grain (or ton) of salt is often the best policy. (For these purposes, btw, if it isn't a journal, it is pretty much "popular press"...) Perry -- Perry E. Metzger Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=33024