Assembly of 3D Microelectronic Blocks by Folding

Integrated circuits are present in every electronic and computational device, and as such, efficient use of space is of major importance. Conventional technology relies on miniaturizing and connecting 2D circuits, but face heating problems and a lower limit restricting the minimum feature size. Although there are a couple of different methods for fabricating three dimensional circuits, they require a considerable amount of manual labor, are serial in nature and result in rather large structures. In this thesis, a new assembly method is presented that combines photolithography, electroplating and self-folding techniques to create micron scale polymeric cubes with circuitry and a microchip on its surface. This process takes advantage of the sequential layers of photolithography and electrodeposition to pattern circuitry on the outside of the planar nets. The folding process produces 3D cubes that minimize the footprint of the circuit. Self-folding is a fabrication technique that forms metallic or polymeric 3D polyhedral shapes from planar precursor nets by harnessing surface forces to drive the folding process. Compared to other methods of forming circuits, this method is highly parallel, minimizes the amount of manual input required and is defect tolerant by nature. Additional applications of these polymer cubes were investigated such as patterning the circuitry on the inside of the cube, to insulate the circuit from the outside environment, and self-assembling the cubic units into a larger ordered computational device with increased processing power. Furthermore, these assemblies will not be plagued by heating issues like traditional computers, and will be able to more efficiently use the available space. Using these methods, progress toward creating a truly 3D computer that mimics the design, power and connectivity of the human brain can be made

Self-assembly of lithographically patterned micropolyhedra

Nature utilizes self-assembly to create structures at a range of length scales. In addition, a variety of biological nanostructures such as viruses have polyhedral geometries and are formed using highly parallel assembly processes. In contrast, it is very challenging to assemble synthetic polyhedra with patterned surfaces at sub-millimeter scales using conventional engineering practices. Inspired by natural fabrication, this thesis is focused on understanding how to assemble such patterned micropolyhedra using both modeling and experiments. Specifically, my work is focused on the development of model polyhedral systems using lithography and self-assembly techniques, demonstrating material versatility and uncovering underlying geometric design rules using mathematical tools. I have investigated an algorithmic approach to self-assemble complex polyhedra such as truncated octahedra. Here, new geometric design rules related to compactness of the precursor nets and pathways were uncovered. I also have studied the influence of pathways and degrees of freedom of intermediates in the assembly of polyhedral isomers and these findings have been compared to geometric models of molecular isomers notably cyclohexane. In addition to a fundamental understanding of self-assembly of polyhedra, I have also explored applications of micropolyhedra. Importantly, I studied a molding process to enhance material versatility and fabricate soft-polyhedra composed of gels and polymers of importance in tissue engineering and biomaterials science. I also describe an approach to use polyhedra patterned with circuits and semiconductor chips to create 3D computational devices by aggregation. In summary, the thesis provides new insight and a robust engineering strategy to mass produce patterned micropolyhedra in a cost-effective manner with material versatility and high yield. In addition to demonstrated applications, we anticipate that these micro polyhedra will offer new capabilities in optics, electronics, robotics, materials science and biomedical engineering