Fabrication of Nanoporous Ultrananocrystalline Diamond Membranes Olga V Makarova * , Ralu Divan ** , Nicolaie Moldovan *** and Cha-Mei Tang * * Creatv MicroTech Inc., 2242 West Harrison St., Chicago IL, 60612 olga@creatvmicrotech.com ** Argonne National Laboratory, 9700 South Cass Av., Argonne IL, 60439 divan@aps.anl.gov *** Advanced Diamond Technologies Inc., 429 B Weber Road #286, Romeoville, IL, 60446 moldovan@thindiamond.com ABSTRACT Nanoporous membranes have a wide range of applications in many fields, including medical diagnostics, drug delivery, and hemodialysis. Ultrananocrystalline diamond (UNCD ® ) coatings are becoming more and more significant in medical applications because of the highest degree of biocompatibility, unmatched by other materials. The 100-nm- and 200-nm-diameter pores have been fabricated in 1-μm-thick UNCD film on silicon wafers using e-beam lithography, reactive ion etching and laser writing. Keywords: ultrananocrystalline diamond, RIE, e-beam lithography, nanonporous diamond membrane 1 INTRODUCTION Nanoporous membranes engineered to mimic natural filtration systems can be used in smart implantable drug delivery systems, bioartificial organs, and other novel nano- enabled medical devices [1]. Some of the key properties required by these membranes are narrow and controlled pore size distribution, high pores density and low thickness to enable high flux, as well as mechanical and chemical stability. Nanoporous silicon [2] and silicon nitride membranes [3] have been used in drug delivery systems [4]; silicon nanopillars [5] were used for capturing circulating tumor cells in blood. Interestingly, irrespective of the regular nature of pore geometry, blocking of pores by proteins or cell debris is still a major problem. Biocompatibility and anti-biofouling are central issues when membranes are used as interfaces in implantable devices. Ultrananocrystalline diamond films are becoming more and more significant in medical applications because of the highest degree of biocompatibility and anti-biofouling, unmatched by other materials [6]. The porous diamond membranes may open new opportunities in implant medicine. Here we report results on high porosity, high-aspect- ratio ultrananocrystalline membranes fabricated using e- beam lithography, reactive ion etching and optical lithography. 2 EXPERIMENTAL The nanoporous membranes were fabricated from 1- μm-thick UNCD films (Aqua 25 UNCD ® , Advanced Diamond Technologies). These UNCD films have the hardness, Young’s modulus, and other extreme properties of natural diamond, as well as smooth (~7 nm rms) surface, and a very low internal stress, which is essential for membrane fabrication [7]. The nanoporous UNCD membrane fabrication followed the sequence shown in Figure 1, as detailed in the following subsections. The optical masks for alignment marks and membrane were fabricated with a LW405 MicroTech laser writer system, and the array of holes was patterned with a Raith 150 e- beam lithography equipment. Figure 1. Illustration of the fabrication of holes and UNCD membrane. NSTI-Nanotech 2010, www.nsti.org, ISBN 978-1-4398-3401-5 Vol. 1, 2010 242