Julian,

There could be some mileage in integrating electrospinning into RP?:
*       J-H He, Y Liu and L Xu, Apparatus for preparing electrospun nanofibres: a comparative review<http://dx.doi.org/10.1179/026708310X12798718274430>, Materials Science and Technology, November 2010, 26(11), 1275-1287.
*       Darrell H Reneker and Alexander L. Yarin [68 references], Electrospinning jets and polymer nanofibers<http://dx.doi.org/10.1016/j.polymer.2008.02.002>, Polymer, 13 May 2008, 49(10), 2387-2425.

Kind regards,
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Dr John Summerscales CEng CEnv CSci
Associate Professor (Reader) in Composites Engineering
School of Marine Science and Engineering
Reynolds Building Room 008
Plymouth University - Plymouth PL4 8AA - England
http://www.plymouth.ac.uk/staff/jsummerscales
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-----Original Message-----
From: Engineers and biologists mechanical design list [mailto:[log in to unmask]] On Behalf Of Julian Vincent
Sent: 20 August 2012 10:10
To: [log in to unmask]
Subject: Rapid Prototyping

I'm writing an essay on possible techniques for manufacturing biomimetic structures - cellular composites and the like - and wonder how advanced RP is, or how advanced it *could* be.  By analogy with the spinneret of the spider it seems reasonable that extrusion-based RP can produce high-performance fibres in which the molecules are assembled at the time of production.  This suggests that it's possible to produce fibrous composites with the orientations requisite for the structure.  Fibres can be orientated in only a single plane, but this is adequate for the cuticle of arthropods.  And although the surfaces currently used are (so far as I know) flat, there is no reason why they should not be of any shape, either programming the third dimension in to the software or using a ranging device (e.g. laser) on the printing head.  Obviously a second extrusion head is needed to provide the matrix.  At present the polymers used in RP are thermoplastic.  I can see that this is simpler in terms of handling than thermoset, but assuming that a thermoset plastic could be crosslinked comparatively quickly, are there advantages in the greater strength or stiffness of thermosets?  An alternative approach is to use a water-based system where the materials either set on contact with (for example) calcium ions in a mass of water within which the object is being made, and/or use hydrophobic/hydrophilic interactions to self-assemble on a surface as they are extruded.  This might require some post-processing for the material to exude excess water, which is what insects do, but aquatic organisms don't need to do this (cf. caddis silk, mussel byssus).
Comments or further thoughts on the above are, as usual, welcomed!

Julian Vincent