Despite the fact that we live in a 3D world and macroscale engineering is 3D, conventional submillimeter-scale engineering is inherently 2D. New fabrication and patterning strategies are needed to enable truly 3D-engineered structures at small size scales. Here, strategies that have been developed over the past two decades that seek to enable such millimeter to nanoscale 3D fabrication and patterning are reviewed. A focus is the strategy of self-assembly, specifically in a biologically inspired, more deterministic form, known as self-folding. Self-folding methods can leverage the strengths of lithography to enable the construction of precisely patterned 3D structures and “smart” components. This self-assembly approach is compared with other 3D fabrication paradigms, and its advantages and disadvantages are discussed.
Frontispiece images reprinted with permission from References25,55,138,80, copyrights 2009, Nature Publishing Group, 2006 and 2007, IOP Publishing, 2001, Conference of Photopolymer Science and Technology, and with permission from Adam Cohen, Microfabrica Inc.