Optimizing microfluidic ink delivery for dip pen nanolithography

In Dip Pen Nanolithography (TM) (DPN (TM)) ultrasharp tips coated with chemical compounds (or ink) are in contact with a surface to produce submicron sized features. There is a need to deliver multiple inks to an array of closely spaced tips (or pens). This work demonstrates the design optimization, fabrication process development, process optimization, and testing of a microfluidic ink delivery apparatus (called inkwells) for simultaneously coating an array of DPN pens with single or multiple inks. The objective of this work is to deliver between four and ten different inks from reservoirs into an appropriately spaced microwell array. The tips of the multipen array are coated with the same or different inks by dipping them into the microwell array. The reservoirs, microwells, and their connecting microchannels were etched in silicon wafers using deep reactive ion etching. Fluid actuation was achieved by capillary flow (wicking). The optimum layouts for different applications were selected with respect to the volume requirement of different inks, the efficacy of ink-well filling, prevention of bubble formation, and the ease of operation (such as dipping and writing) with a parallel array of pens. (c) 2005 Society of Photo-Optical Instrumentation Engineers.