A bio-pen for direct writing of single molecules on user-functionalized surfaces.

Advancing ultrahigh resolution (below 10 nm) direct writing technologies could lead to impacts in areas as diverse as disease detection, genetic analysis and nanomanufacturing. Current methods based on electron-beams and photo- or dip-pen nanolithography are laborious and lack flexibility when aiming to create single molecule patterns for application specific integration. We hypothesize that a novel strategy could be developed to allow for writing of parallel and yet individually addressable patterns of single molecules on user-controlled surfaces. The strategy is based on using in vitro self-recognition of tubulin protein to assemble rigid protofilaments of microtubules, with one such microtubule to be subsequently used as a "bio-pen" capable of writing "inks" of single kinesin molecules in user-defined environments. Our results show that single kinesin inks could be written under the energy of adenosine triphosphate hydrolysis and observed by both atomic force and optical microscopy. Upon extending ink functionalities, the integration of soft and hard materials for nanostructure assembly and complex single molecule pattern formation is envisioned.