X-Message-Number: 1110
From:	Ralph Merkle <>
Subject: Low temperature operation of nanomachines
Date:	Thu, 6 Aug 1992 17:16:24 PDT

Most of the proposed devices in "Nanosystems: Molecular Machinery,
Manufacturing, and Computation" are intended to function at around
300 K (room temperature).  The atomically precise basically
mechanical devices designed to function in a vacuum would, for
the most part, also function at lower temperatures.  Levers,
gears, bearings, rotating shafts, springs, rod logic, etc.
would all function at arbitrarily low temperatures.  Devices
designed to operate in liquids (such as water) would presumably
cease to function when the liquid froze.

At low temperatures, thermal activation of chemical reactions would
be less effective.  This can be compensated for by using either mechanical
forms of energy (pushing, pulling) to provide the activation energy
required, or by using highly reactive compounds (radicals, carbenes,
etc.) which have very low activation energy.  Synthesis of structures
in vacuum using highly reactive compounds and mechanical sources for
activation energy could be done at arbitrarily low temperatures.
Reactions which require thermal activation energy could not be used
at lower temperatures.

There seem to be no fundamental problem in designing systems that would
function at low temperature.  Many design techniques are temperature
insensitive.  In the long run, it is likely that the design costs for
most feasible devices that we can envision today (including devices that
operate at low temperature) will be quite low.  However, it seems likely
there will be a period during which some types of devices will be easier
and less costly to design and build than other types of devices.  It is
difficult for me to tell exactly which devices will be cheap and
easy to design during this interim period.

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