Microfluidic device for delivery of multiple inks for dip pen nanolithography
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In the dip pen nanolithography (DPN) 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 PEG) 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. 2007 Society of Photo-Optical Instrumentation Engineers.