Molecular printing: A chemist´s approach to a “desktop fab”

Summary form only given. We have developed an arsenal of strategies based on a scanning probe molecular printing method [Braunschweig, et. al., 2009] recently developed in our group, namely polymer pen lithography (PPL) [Huo, et. al., 2008], to form arbitrary patterns of molecular and biological species with nanometer-to-micrometer feature size control. PPL employs massively-parallel arrays of elastomeric tips to print arbitrary patterns of molecular inks. The precise feature size control of PPL arises from quantitative models relating dwell-time of the tips on the surface and the pressure exerted by the tips on the surface [Liao, et. al., Small, 2010]. Moreover, these relationships allow the precise leveling of the tip arrays with respect to the substrate surface, so that feature variation of less than 2% across a 1 cm² areas can be achieved [Liao, et. al., Nanoletters, 2010]. Importantly, the molds used to fabricated the PPL pen arrays can also serve as inkwells, and as a result, multiplexed patterns can be readily created using these methods [Zheng, et. al., 2009]. These tools have been used to explore the concept of directed assembly, which has been employed to assemble a variety of devices, including biosensors and molecular tunnel junctions. We anticipate that these strategies will result in a suite of new molecular printing methods that move us towards the goal of a “desktop fab,” in which reproducible, nanoscale patterns can be printed over large areas without necessitating large capital investment or clean-room conditions.