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Scaffold Material with a Self-Stabilizing Structure Europaisches Patentamt ||||||| |||||| ||| ||||| ||||| ||||| ||||| ||||| ||||| ||||| ||||| |||||| |||| |||| ||| (1 9) Qjl) European Patent Office Office euroDeen des brevets (11) EP 0 963 834 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) int. CI.6: B29C 67/00, B22C 7/02, 15.12.1999 Bulletin 1999/50 E04G 1/00, A61 L 27/00, (21) Application number: 98304496.7 D04H 1 3/00, B01 D 39/1 4 (22) Date of filing: 08.06.1998 (84) Designated Contracting States: (72) Inventor: Ingber, Donald E. AT BE CH CY DE DK ES Fl FR GB GR IE IT LI LU Boston, Massachusetts 021 1 6 (US) MCNLPTSE Designated Extension States: (74) Representative: AL LT LV MK RO SI Greenwood, John David et al Graham Watt & Co. (71) Applicant: Riverhead Molecular Geodesies, Inc. Sevenoaks Kent TN13 2BN (GB) Boston, Massachusetts 02199 (US) (54) Scaffold material with a self-stabilizing structure (57) A scaffold material is provided which com- prises a predetermined arrangement of integrally con- nected modules, each said module comprised of a plurality of integrally connected elongated members forming at least a portion of a polyhedron, the members arranged such that at least a portion of said members form geodesic or tensegrity elements. The scaffold material can be used in various ways, such as in filtration material, catalysis, protective textile fabrics, production of patterns for making moulds by shell investment casting, and biomedical applications, e.g. detoxification. < CO CO CO CO <7> o Q_ LU Printed by Xerox (UK) Business Services 2.16.7/3.6 1 EP 0 963 834 A1 2 Description vide a material having novel mechanical and bioactive properties. It is a further object of the invention to pro- Field of the Invention vide a material useful as a protective shield or textile and for filtration, detoxification and biomedical applica- [0001] This invention relates to three-dimensional 5 tions. structures which possess geodesic features and can [0006] The present invention describes three-dimen- stabilize through use of tensegrity. sional biomimetic scaffold materials which possess geodesic features, can stabilize through use of tenseg- Background of the Invention rity and may be fabricated as unitary structures on the 10 micro or macro scale. [0002] There is a need to develop new light-weight, [0007] In one aspect of the invention, a scaffold mate- porous materials that exhibit enhanced mechanical rial is provided which possesses a predetermined strength, flexibility and exposed surface as scaffolds for arrangement of integrally connected modules, each detoxification, filtration, catalysis, textile fabrics, space- said module comprised of a plurality of integrally con- filling, space-covering and biomedical applications. The 15 nected elongated members forming at least a portion of ultimate material would be biomimetic materials that a polyhedron, the members arranged such that at least mimic the mechanical responsiveness and bioprocess- a portion of said members form geodesic or tensegrity ing capacities of living cells and tissues. elements. [0003] Living cells and tissues use tensegrity architec- [0008] By "scaffold," as that term is used herein, it is ture to organize and mechanically stabilize their internal 20 meant a material having an extended repeating struc- filamentous support networks (interconnected nuclear ture, which forms a framework or skeleton onto which matrix, cytoskeletal, and extracellular matrix scaffolds) and into which additional components may be intro- and hence, their three dimensional forms (see, J. Cell duced to impart additional features to the material. Sci. 104:613,1993). The concept of tensegrity is well- [0009] By "module," as that term is used herein, it is known in the fabrication of geodesic structures, such as 25 meant a plurality of integrally connected structural geodesic domes. See, for example, U.S. Patent Nos. members that delineate the edges of at least a portion 3,063,521, 3,354,591 and 4,901,483. Tensegrity con- of a polyhedron. struction is based upon the realization that most build- [001 0] By "integrally connected," as that term is used ing materials are much more efficiently utilized and can herein, it is meant a single composition or structure often withstand higher forces when in tension than 30 made up of a plurality of elements to form a single uni- when in compression. In tensegrity construction, there tary body. The structure does not posses discrete con- is a high ratio of tension to compression elements. The nectors or additional bonding or adhesive materials. tension members in these structures are geodesic ele- [0011] By "geodesic element," as that term is used ments that delineate the shortest distance between ver- herein, it is meant a geometric element which defines tices that define an enclosed polyhedron. The 35 the shortest distance between two points on the surface mathematical modeling rules for the building and of a solid. For example, a line is the shortest distance designing of tensegrity structures is also well under- between two vertices on a surface of a polyhedron, a stood. See, for example, Kenner in Geodesic Math path along a great circle is the shortest distance (and (1980) in which the basic mathematics defining the ori- hence, a geodesic element) for a sphere, and a spiral is entation of individual structural elements within simple 40 a geodesic element on the surface of a cylinder. A trian- tensegrity modules is described. These models have gle is geodesic because it represents the shortest, most been directed to macrostructures suitable for use in economical path between three vertices on the surface large-scale objects, such as buildings and toys. See, of a polyhedron. U.S. Patent No. 3,695,617. These macrostructures have [0012] By "tensegrity element," as that term is used been prepared by joining individual elements in the 45 herein, it is meant an arrangement of interconnected desired three dimensional arrangement and hence are structural members that self-stabilizes through trans- not well suited to miniaturization. mission of continuous tension and discontinuous com- [0004] Thus, there remains a need to prepare materi- pression. Tensegrity elements may be composed of als which can exhibit the mechanical responsiveness members that selectively resist tension or compression and bioprocessing capabilities of living cells and tis- so locally or of all non-compressible members that may sues. This invention is based on recent advances that resist either tension or compression depending on their have been made in our understanding of the relation location and the path of force transmission. A triangle between microstructure and macroscopic behavior in composed of all non-compressible struts is an example living cells and tissues. of the latter type of self-stabilizing tensegrity structure. 55 [0013] By "extensible element," as that term is used Summary of the Invention herein, it is meant an element that is capable of exten- sion or an increase in the length of the member within a [0005] It is an object of the present invention to pro- given range of movement in response to application of a 2 3 EP 0 963 834 A1 4 tensile force to one or both ends of the member. closed octahedral tensegrity structure that exhibits [001 4] By "non-compressible element," as that term is a "dog-leg" geometry; used herein, it is meant an element that is incapable of Figure 8 is a computer simulation illustrating a shortening along its length when compressive forces series of dynamic geometric transformations within are applied to one or both ends of the member. How- s three cuboctahedron modules that are joined along ever, the non-compressible member may be able to a common triangular face, which is capable of rear- buckle under compression, without shortening its ranging from a linear, flexible cuboctahedral array to length. A non-compressible member may or may not be form a nonlinear, rigid, closed octahedral tensegrity able to extend in length when external tensile forces are arrangement different than that shown for Fig. 6; applied to its ends. Such an extensible, non-compressi- 10 Figure 9 is an illustration of a scaffold material ble member would be able to withstand compression, coated with a hydrogel (Fig. 9a) and impregnated but not tension. with an additional detoxification agent (Fig. 9b); Figure 10 is a computer simulation illustrating that Brief Description of the Drawing the addition of larger fibers that are stiff, yet flexible, 15 to a modular network results in the increased resist- [0015] The present invention is described with refer- ance to distortion and a tensegrity network that stiff- ence to the following Figures, which are presented for ens and is held open when stressed; the purposes of illustration only and which are by no Figure 11 is an illustration of a geodesic material means intended to be limiting of the invention and in composed of all extensible members arranged into which: 20 a spherical module; Figure 12 is an illustration of two cuboctahedron in Figure 1 is an illustration of a cuboctahedron mod- different stages of contraction and rearrangement ule containing non-compressible elongated mem- which demonstrates that the individual modules are bers which can rearrange to self-stabilize through not required to behave in a concerted fashion; and tensegrity; 25 Figure 13 is an illustration of a computer model of Figure 2(a) illustrates a hierarchical, nucleated the deformation of two linked cuboctohedra (Fig. tensegrity "cell" model composed of sticks and 13a and 13b), and of the corresponding deforma- strings and Figure 2(b) illustrates the coordinated tion of two linked cuboctohedra fabricated by spreading of the cell and nucleus that occurs when CAD/CAM methods (Fig. 13c and 13d). living cells adhere to an adhesive substrate; 30 Figure 3 is a plot of mechanical stiffness (ratio of Detailed Description of the Invention stress to strain) v.
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