Re: interesting work

Date: Wed May 19 1999 - 00:25:31 EEST

In a message dated 99-05-18 16:42:14 EDT, writes:

<< Subj: interesting work
 Date: 99-05-18 16:42:14 EDT
 From: (Elaine Hunt)
 Mineralization of multilayer hydrogels as a model for mineralization of bone
  Author(s): Calvert, Paul; Frechette, Joelle; Souvignier, Chad
  Author Affiliation: Univ of Arizona
  Source: Materials Research Society Symposium - Proceedings Materials
 Science of the Cell Proceedings of the 1997
  MRS Fall Meeting Dec 1-4 1997 v489 1998 Boston, MA, , USA, Sponsored by :
 MRS MRS Warrendale PA USA p
  153-159 0272-9172 MRSPDH
  Abstract: Extrusion freeform fabrication is a 3-D layerwise writing
 technique for forming objects directly under the control of a CAD program.
 This method is one of a family of rapid prototyping methods which include
 stereolithography, selective laser sintering and fused deposition modeling.
 This system can be used to build shapes, layer by layer, from hydrogels of
 agarose, polyacrylamide or other cross-linked water-soluble acrylic
 polymers. Mineralization can be induced in these gels by building a part
 with alternating layers of gels containing calcium and carbonate or
 phosphate that can be formed into stacks which then mineralize by
 cross-diffusion. The write head can be conceived of as a cell which
 delivers the appropriate minerals to a site within a swollen gel matrix.
 This diffusive mineralization process can thus be compared with bone
 mineralization. The gel structure controls the morphology of the
  mineral. The site of mineralization is controlled by osmotic forces which
 localize most of the mineral in whichever zone has the higher ionic
 strength. The mineral content, expressed as a fraction of the polymer
 content, is similar to that of
  bone but the water content is much higher than in bone. This raises the
 question of what process drives the water exclusion during bone
  English (Author abstract) 9 Refs. Subjects: Hydrogels Polyacrylates;
 Biomaterials; Multilayers; Bone; Extrusion; Computer aided design;
  Crystal structure; Morphology; Ionic strength; Swelling; Computer software;
  Classification Codes: 801.3; 804; 815.1.1; 462.5; 933.1; 461.2
  Document Type: CA
  Identifiers: Polyacrylamide; Agarose; Mineralization



The method struck a familiar chord. Came across this US patent from Battelle
5697043 : Method of freeform fabrication by selective gelation of powder
INVENTORS: Baskaran; Suresh, Kennewick, WA Graff; Gordon L., Kennewick, WA
ASSIGNEES: Battelle Memorial Institute, Richland, WA
U.S. CLASS: 419/030
ABSTRACT: The present invention is a novel method for freeform fabrication.
Specifically, the method of solid freeform fabrication has the steps of:
(a) preparing a slurry by mixing powder particles with a suspension medium
and a gelling polysaccharide; (b) making a layer by depositing an amount of
said powder slurry in a confined region; (c) hardening a selected portion of
the layer by applying a gelling agent to the selected portion; and (d)
repeating steps (b) and (c) to make successive layers and forming a layered
object. In many applications, it is desirable to remove unhardened material
followed by heating to remove gellable polysaccharide then sintering. XX

We have seen the future, and it is Jell-O.

Ed Grenda
Castle Island Co.
19 Pondview Road
Arlington, MA 02474 USA
781-646-6280 (voice or fax) (email)

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