Evolution from dip-pen nanolithography to mechanochemical printing

Abstract

<sec>As a unique nanomanipulation and nanofabrication tool, dip-pen nanolithography (DPN) has enjoyed great success in the past two decades. The DPN can be used to create molecular patterns with nanoscale precision on a variety of substrates with different chemistry properties. Since its advent, the DPN has been steadily improved in the sense of applicable inks, fabrication throughput, and new printing chemistry. Among these developments, mechanical force induced mechanochemistry is of special interest.</sec><sec>In this review, we introduce the physical principles behind the DPN technique. We highlight the development of DPN for writing with various types of “inks”, including small molecules, viscous polymer solutions, lipids, and biomolecules, especially, the development of thermal-DPN allowing printing with inks that are usually in solid phase at room temperature. Next, we introduce the parallel-DPN and polymer pen nanolithography. These techniques greatly speed up the fabrication speed without sacrificing the precision. We also summarize the advances in chemical reaction based DPN technologies, including electrochemical DPN, metal tip-induced catalytical DPN, and mechanochemical DPN (or mechanochemical printing). To further elaborate the mechanism behind the mechanochemical printing, we briefly review the development of mechanochemistry, including the reaction mechanism, various experimental approaches to realizing mechanochemistry, and recent development in this field. We highlight the advantages of using atomic force microscopy to study mechanochemistry at a single molecule level and indicate the potential of combining this technique with DPN to realize mechanochemical printing. We envision that with the further discovery of novel mechanophores that are suitable for mechanochemical printing, this technique can be broadly applied to nanotechnology and atomic fabrication.</sec>