MASSIVELY PARALLEL MULTI-TIP NANOSCALE WRITER WITH FLUIDIC CAPABILITIES – FOUNTAIN PEN NANOLITHOGRAPHY (FPN) K.-H. Kim, C. Ke, N. Moldovan, H.D. Espinosa Department of Mechanical Engineering, Northwestern University 2145 Sheridan Road, Evanston, IL 60208 ABSTRACT Arrays of atomic force microscope (AFM) probes were developed for applications of dip-pen nanolithography (DPN), which is capable of surface patterning with functionalized bio-molecules and can be used to construct biological and chemical sensors. Microchannels were embedded in AFM probes to transport ink or bio-molecules from reservoirs to substrates, realizing continuous writing at the nanoscale. This so-called “fountain-pen nanolithography” (FPN) device was developed using surface and bulk micromachining. A volcano tip, which is a completely novel design for microfluidics, was built at the end of the AFM probe as a dispensing mechanism. Numerical simulations were performed to evaluate flow characteristics and the optimal materials for the volcano-tip probes. The results determined the selection of appropriate materials and the design of microfabrication steps. Multi- layer films and thermal oxidation were used to integrate volcano tips and microchannels into AFM probes. The proposed FPN devices will likely expand the capabilities of surface functionalization and manipulation at the nanoscale in a massively parallel way. 1. INTRODUCTION Nanopatterning capability is indispensable to fabricate and investigate the nanoworld. Dip-pen nanolithography (DPN) provided an affordable direct writing process, capable of a few tens of nanometers resolution, using atomic force microscopy (AFM) tips [1]. In DPN, molecules are delivered to a surface through a water meniscus. DPN with multiple inks [2] and multiple commercial tips [3] was employed to expand its capability in terms of patterning of multi-species and patterning speed. One disadvantage of DPN in the current stage is that the writing species need to be replenished periodically, requiring the AFM probe to be dismounted, which interrupts the writing process. Several studies reported upon methods that can be utilized to overcome the ink supply drawbacks in conventional DPN. Quartz microprobes, produced by pulling capillary micropipettes, were introduced as an alternative to conventional microfabricated cantilevers [4-6]. Moreover, a pulled micropipette with a small aperture (300 nm diameter) was used to continuously deliver photoresist to a substrate enabling chemical reaction and repair of nanoscale structures [7]. A drawback of these micropipettes is the difficulty in arraying, which is essential to overcome another disadvantage of the conventional DPN, the low speed writing, inherent to the AFM motion. As an effort to AFM probe Reservoir Bending actuator Microchannel (a) (b) (c) (d) Figure 1. Schematic showing the concept of massively parallel cantilevers: (a) arrays of the device on a on wafer, (b) zoom-in view of a unit cell with a feeding reservoir, (c) embedded microfluidics network, (d) a cantilever with a dispensing tip, a microchannel and a bending actuator for vertical motion control. silic 235 Proceedings of the 4th International Symposium on MEMS and Nanotechnology, the 2003 SEM Annual Conference and Exposition on Experimental and Applied Mechanics, June 2-4, Charlotte, North Carolina, Session 52, Paper 191, pp. 235-238, 2003.