Paper NS-TuP2
Uniform Printing of PEG Hydrogel Arrays by Dip-Pen Nanolithography^®

Tuesday, October 19, 2010, 6:00 pm, Room Southwest Exhibit Hall

Dip Pen Nanolithography^® (DPN^®) is an established method of nanofabrication in which materials are deposited onto a surface via a sharp tip. DPN enables controlled deposition of a variety of materials with nanoscale registry onto various substrates. Recent advances in DPN technology has resulted in the ability to directly print larger, biologically relevant materials on to a variety of surfaces under ambient conditions.

A novel method for the construction of hydrogel patterns has been developed. Hydrogels are of great interest to tissue engineers and other biomedical researchers because of the versatility of PEG chemistry and excellent biocompatibility. Also the mechanical and swelling properties of PEG hydrogels can be easily tuned by controlling the degree of cross-linking and choosing the appropriate molecular weight. Patterning of hydrogels in submicron scale with defined mechanical properties is highly desirable as a scaffold for tissue engineering and in vitro cell culture studies.

We report a novel method for generation of hydrogel patterns at subcellular scales. Hydrogel precursors are directly deposited at defined location and then polymerized to form hydrogels. This method allows for rapid fabrication of high resolution patterns. We used a simple desktop nanolithography platform (NLP 2000™, NanoInk, Inc.) for the deposition of the hydrogel precursors. The NLP 2000 consists of a stacked 3axis stage system with a travel range of 40 mm and a resolution of 25 nm. A high resolution optical microscope is available for monitoring the printing process. A custom fabricated array of cantilever based writing tools (M-Type, 12-pen, NanoInk, Inc.) were used to transport the hydrogel precursors on to the surface. Controlling the environmental conditions during the printing process allows for the transfer of defined volumes of hydrogel precursors. At 37°C, hydrogel domains of 6 μm were printed while at 25 °C 1.5 μm domains were printed. Patterning areas of 1 mm² with domains of less than 5 μm can be easily achieved in less than 30 min. AFM result confirmed the size and homogeneity of the printed hydrogel patterns.