Depositing a wide range of materials as nanoscale features onto diverse surfaces with nanometer registration and resolution are challenging requirements for any nanoscale processing system. Dip Pen Nanolithography® (DPN®), a high resolution, scanning probe-based direct-write technology, has emerged as a promising solution for these requirements. Many different materials can be deposited directly using DPN, including alkane thiols, metal salts and nanoparticles, metal oxides, polymers, DNA, and proteins. Indirect deposition allows the creation of many interesting nanostructures. For instance, using MHA may be used to create arrays of antibodies, which then bond specifically to antigens on the surface of viruses or cells, to create cell or virus arrays. The DPN system is designed to allow registration to existing features on a writing substrate via optical alignment or nanoscale alignment using the core AFM platform. This allows, for instance, the nanoscale deposition of sensor materials directly onto monolithic electronic chips with both sensing and circuit features.
To enable the DPN process, novel pen and ink delivery systems have been designed and fabricated using MEMS technology. These MEMS devices bridge the gap between the macro world (instrument) and the nano world (nanoscale patterns). The initial MEMS devices were simple and robust both in design and fabrication to get products into the marketplace quickly. The first MEMS-based DPN device was a passive pen array based on silicon nitride AFM probe technology from Cal Quate's group at Stanford. The next two devices (an inkwell chip and a thermal bimorph active pen) were more complicated and took considerable effort to commercialize. In this work, some of the difficulties in bringing brand new MEMS devices from the prototype stage into production will be shared. The subsequent MEMS products have become even more complicated both in design and fabrication, but the development process has improved as well. For example, the 2D nanoPrintArray has 55,000 pens in one square centimeter for high throughput writing over large areas. The 2D arrays enable templated self assembly of nanostructures giving researchers the ability to control the placement of self assembled features rather than allowing the self assembly to occur randomly.
Applications of DPN technology vary from deposition of DNA or proteins in nanoarrays for disease detection or drug discovery, to deposition of Sol-gel metal oxides for gas sensors, and to additive repair of advanced phase-shifting photomasks.