Microfluidic device for delivery of multiple inks for dip pen nanolithography

Abstract

In the dip pen nanolithography ͑DPN͒ process, ultra-sharp scanning probe tips ͑"pens"͒ are coated with chemical compounds ͑or "ink"͒ and contacted with a surface to produce submicron-sized features. This work describes the design, fabrication, and testing of a microfluidic ink delivery device for delivering multiple species of inks to an array of multiple pens, as well as for maximizing the number of inks for simultaneous patterning by DPN. The microfluidic device ͑called "Centiwell"͒ consists of a 2-D array of 96 microwells that are obtained by silicon bulk micromachining process. A thermoelectric module is attached to the bottom of the substrate. Microbeads of a hygroscopic material ͑e.g., polyethylene glycol or PEG͒ are dispensed into the microwells. The thermoelectric module cools the substrate to below the dew point for condensing water droplets on the microbeads and to create PEG solutions that serve as the ink for DPN. An array of pens is then coated with the ink. Subsequently, nanolithography is performed with the coated pens. Multiple PEG nanopatterns obtained by this method are presented as proof-of-concept. This demonstrates the functionality of the Centiwell microfluidic ink delivery device for nanolithography of multiple inks. Also, fractal nanopatterns are observed in the nanolithography experiments.

Simplistic Model for the Dendritic Growth of a Monolayer in Dip Pen Nanolithography

“…It is encouraging that a mere change in directional coherence produces such a variety of patterns with different complexity ranging from a circle or hexagon to dendrites. We did not however try to reproduce the random and fractal dendrites observed in DPN experiments. , Our goal here was to show that the model gives self-replicating branches characteristic of dendrites and captures the essential features of MD simulation for thiols on gold. A further improvement of the model and a possible reproduction of experimental dendrites will be the next step.…”

“…6,7 In this dip pen nanolithography (DPN), 8,9 a tip continuously creates nanodroplets that subsequently spread to form a monolayer over a surface (Figure 1a). A micrometer-sized dendrite was observed in the DPN of dodecylamine 6 or polyethylene glycol 7 on mica. This is in stark contrast to the isotropic and circular monolayer patterns obtained with conventional DPN (e.g., alkanethiol on gold).…”

“…The dendritic growth of structures has interested researchers in many areas, with applications to processes such as the solidification of supercooled liquids, , electropolymerization, and epitaxial film growth . It was recently reported that a dendritic monolayer of organic molecules can be grown by using a nanometer tip as a point source of molecular deposition. , In this dip pen nanolithography (DPN), , a tip continuously creates nanodroplets that subsequently spread to form a monolayer over a surface (Figure a). A micrometer-sized dendrite was observed in the DPN of dodecylamine or polyethylene glycol on mica.…”

“…It was recently reported that a dendritic monolayer of organic molecules can be grown by using a nanometer tip as a point source of molecular deposition. , In this dip pen nanolithography (DPN), , a tip continuously creates nanodroplets that subsequently spread to form a monolayer over a surface (Figure a). A micrometer-sized dendrite was observed in the DPN of dodecylamine or polyethylene glycol on mica. This is in stark contrast to the isotropic and circular monolayer patterns obtained with conventional DPN (e.g., alkanethiol on gold).…”

Toward conductive traces: Dip Pen Nanolithography® of silver nanoparticle-based inks

“…We inked the tips using NanoInk Inkwells™ in order to control both the amount of ink delivered to the tip, and the extent of the ink wicking onto the surrounding cantilever. 11 We pipetted the ink solution into the Inkwell reservoir, whereafter it flowed into the tip-sized microfluidic well. This was coordinated by standard NSCRIPTOR inking routines ͑i.e., AFM scanner-controlled vertical movements͒.…”