"Active Fabric"

Forrest Bishop (forrestb@ix.netcom.com)
Sun, 9 Mar 1997 21:26:16 -0600 (CST)


This might help. It is part of a chapter in
"Tools for the Next Millenia", CRC Press

Copyright (c) 1997 Forrest Bishop, All Rights Reserved

Active Fabric, A Skin for All Seasons
by Forrest Bishop
Institute of Atomic-Scale Engineering, Seattle, Washington, USA

An ideal spacesuit should be skin-tight and able to move effortlessly
with the body. If it is made of a fabric that can change its area, as
well as continue to maintain a particular "springiness", a suit made of
it would
be able to maintain a one-atmosphere pressure against the wearer's skin
even as she moves around. The inside surface of this second skin can
have a second circulatory system embedded in it to supply oxygen and
carry away
sweat from the underlying skin.
One way of making such a suit is with something I call "Active
Fabric", a material that can change its area. This stuff is made up of
layers of plates in shapes that tile the plane [Penrose], such as
squares, rectang
les or hexagons (Figure). Two or more layers of these tiles are offset
from each other by half the width of the tile. For human bodies, these
plates can be quite large by nanotech standards, from a few microns to
a millimeter across, and made of either diamondoid (carbon or silicon),
ceramics, or possibly even metal. The layers of plates are connected
together by sliding joints similar to my XY Active Cell interface
[Bishop]. For
square plates for example, the movement is at 45 degrees to the edge of
the plate. This allows, (without considering a cascade of plates) an
areal variation of something less than 400%, much more than is really
needed for
the spacesuit proper.
To move two layered plates apart, a rack-and-pinion might work
[Globus, Drexler], or a comb of linear molecules with "beads" on them
that can take up various positions along the molecule [REF]. This also
is what provid
es the two-dimensional compressive strength of the fabric. Buckling is
prevented by the pressure of the enclosed body.
To bring the sets of plates together, a network of fibers is
attached to some of the inside layer of plates. At one end of a fiber
might be a nanoscale winch, driven by a tiny motor, or something like
the molecule that
the {bacterium harpoon from Foresight gathering}assembles and
disassembles on the fly [REF]. These fibers also only need to extend
for twice their length, so some molecule that does this with suitable
chemical or electri
cal prompting might make a clean solution, akin to muscle fiber
contraction [actin REF]. Another possibility is so-called 'memory
metal", or Nitinol, which can be made to contract when it is cooled.
With this basic core of the fabric, different flexiblelayers can be
laminated on either side, for other purposes than simple vaccum
environmental support. The layer against the skin of the wearer can
contain embedded s
ensors for pressure, temperature, water, chemicals, and so on, to help
make things comfortable. An active gas circulatory system might
maintain a very thin nitrogen/oxygen gas layer between the skin and the
suit, tricking
the natural sensors of the living skin into thinking they are in free
air (nude). This only works on shaved areas. Variable reflectivity
layers can help with temperature control, as can the circulatory
The exterior layers can be almost anything. For harsh chemical
environments, a teflon or neoprene coating could be used, much like
what is already available. For more general use, one would probably
want an active o
ptical surface of some kind, perhaps Phased Array Optics [Wouk] to
generate three dimensional displays. This kind of display, along with
optical sensors and digital signal prossors (DSPs) can form the basis
of a "cloaking
device", or invisibility suit similar to the one the alien wore in the
film "Predator". A TFT-style flexible membrane like on a laptop can
display clothes, pictures, or movies for more sociable occasions.