Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-03-13
2003-01-21
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
Reexamination Certificate
active
06507989
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to self-assembly, and more particularly to surface-selective self-assembly of component articles, including those spanning the micron to centimeter range and optionally including electronic circuitry, into composite articles.
BACKGROUND OF THE INVENTION
Self-assembly is a term used to define the spontaneous association of entities into structural aggregates. The best-known and most well-researched area of self-assembly involves molecular self-assembly, that is, the spontaneous association of molecules, a successful strategy for the generation of large, structured molecular aggregates. Self-assembly of molecules in solution is described by Whitesides, et al., in “Noncovalent Synthesis: Using Physical-organic Chemistry to Make Aggregates”,
Accts. Chem. Res.,
28, 37-44 (1995). See also Philp, et al.,
Angew. Chem., Int. Ed. Engl.,
35, 1155-1196 (1996) for molecular self-assembly. Nature includes examples of molecular self-assembly where, in the field of biology, many processes involve interfacial interactions and shape selectivity to form complex, three-dimensional structures.
Self-assembly of molecules can be made to occur spontaneously at a liquid/solid interface to form a self-assembled monolayer of the molecules when the molecules have a shape that facilitates ordered stacking in the plane of the interface and each includes a chemical functionality that adheres to the surface or in another way promotes arrangement of the molecules with the functionality positioned adjacent the surface. U.S. Pat. No. 5,512 131, and U.S. patent application Ser. Nos. 08/695,537, 08/616,929, 08/676,951, and 08/677,309, and International Patent Publication No. WO 96/29629, all commonly-owned, describe a variety of techniques for arranging patterns of self-assembled monolayers at surfaces for a variety of purposes. See also Whitesides, G. M., “Self-Assembling Materials”,
Scientific American,
273, 146-149 (1995) for a discussion of self-assembly.
Self-assembly of components larger than molecules is known, for example, self-assembly of bubbles at an air-liquid interface, small spheres self-assembled on surfaces, self-assembly of microspheres via biochemical attraction between the microspheres, and the like. In “A DNA-Based Method for Rationally Assembling Nanoparticles Into Macroscopic Materials”,
Nature,
382, (Aug. 15, 1996), Mirkin, et al., describe a technique for assembling colloidal gold nanoparticles, reversibly, into macroscopic aggregates. Non-complementary DNA oligonucleotides capped with thiol groups that bind to gold are attached to the surface of batches of 13 nm gold particles. When the particles are placed into a solution to which is added an oligonucleotide duplex with “sticky ends” complementary to the two grafted sequences, the nanoparticles self-assemble into aggregates. The assembly can be reversed by thermal denaturation. Yamaki, et al., in “Size Dependent Separation of Colloidal Particles in Two-Dimensional Convective Self-Assembly”
Langmuir,
11, 2975-2978 (1995), report “convective self-assembly” of colloidal particles ranging in size from 12 nm to 144 nm in diameter in a wetting liquid film on a mercury surface. Size-dependent two-dimensional convective assembly occurred, with larger particles being positioned in the center of the aggregate and smaller particles at the periphery. Cralchevski, et al., in “Capillary Forces Between Colloidal Particles”
Langmuir,
10, 23-36 (1994), describe capillary interactions occurring between particles protruding from a liquid film due to the capillary rise of liquid along the surface of each particle. A theoretical treatment of capillary forces active spheres is presented. Simpson, et al., in “Bubble Raft Model for an Amorphous Alloy”,
Nature,
237-322 (Jun. 9, 1972), describe preparation of a two-dimensional amorphous array of bubbles of two different sizes as a model of an amorphous metal alloy. The bubbles were held together by a general capillary attraction representative of the binding force of free electrons in the metal.
U.S. Pat. No. 5,45,291 (Smith) describes assembly of solid microstructures in an ordered manner onto a substrate through fluid transfer. The microstructures are shaped blocks that, when transferred in a fluid slurry poured onto the top surface of a substrate having recessed regions that match the shapes of the blocks, insert into the recessed regions via gravity. U.S. Pat. No. 5,355,577 (Cohn) describes a method of assembling discrete microelectronic or micro-mechanical devices by positioning the devices on a template, vibrating the template and causing the devices to move into apertures. The shape of each aperture determines the number, orientation, and type of device that it traps.
While self-assembly at the molecular level is relatively well-developed, self-assembly at larger scales is not so well-developed. Many systems in science and technology require the assembly of components that are larger than molecules into assemblies, for example, microelectronic and microelectrochemical systems, sensors, and microanalytical and microsynthetic devices. Photolithography has been the principal technique used to make microstructures. Although enormously powerful, photolithography cannot easily be used to form non-planar and three-dimensional structures, it generates structures that are metastable, and it can be used only with a limited set of materials. Accordingly, it is an object of the present invention to provide techniques for the rational self-assembly of component articles into composite structures according to predetermined arrangements.
SUMMARY OF THE INVENTION
The present invention provides techniques for self-assembly of component articles. In one aspect, the invention provides a method of self-assembly including providing a first component article having a maximum dimension, a total surface area, and a first mating surface. A second component article is provided that also has a maximum dimension, a total surface area, and a second mating surface that matches the first mating surface of the first component article. The first and second mating surfaces each define an area equal to at least 1% of the lesser of the total surface areas of the first and second component articles. Preferably, the first and second mating surfaces each define an area equal to at least 5% of the lesser of the total surface areas of the first and second component articles, more preferably at least 10%. The first and second component articles are separated by a distance at least equal to {fraction (1/100)} of the maximum dimension of the first or second component article, preferably separated by a distance at least equal to {fraction (1/50)} the maximum dimension, preferably at least {fraction (1/25)}, and more preferably still a distance at least equal to the maximum dimension. Then, without applying a net external force to either of the first and second component articles, and under set conditions, the first mating surface is allowed to fasten to the second mating surface in a manner that is irreversible under the set conditions. A composite article of the first and second component articles is thereby formed. In another embodiment the method involves allowing the first and second mating surfaces to mate in the presence of a net external force. A third component article can be added to the system and the method can involve allowing a mating surface of the third article to fasten to the mating surface of the second component, irreversibly under the set conditions.
According to another embodiment the invention involves a method of self-assembly that includes first and second component articles each including a total surface area, a first mating surface, and a remainder surface. The first and second mating surfaces each are compatible with the other and are incompatible with the remainder surfaces. Without applying a net external force to either of the first and second component articles, and under set conditions, the first mating surface is allowed to fasten to the sec
Bowden Ned B.
Carbeck Jeffrey D.
Terfort Andreas W.
Whitesides George M.
Arbes Carl J.
President and Fellows of Harvard College
Wolf, Greenfield & Sacks, P.C
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