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

Abstract

We have developed an arsenal of strategies based on a scanning probe molecular printing method1 recently developed in our group, namely polymer pen lithography (PPL),2 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 (Fig. 1A). 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.3 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.4 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 (Fig. 1B).5 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.