Published: August 12, 2011 r2011 American Chemical Society 3666 dx.doi.org/10.1021/am200852w | ACS Appl. Mater. Interfaces 2011, 3, 3666–3672 RESEARCH ARTICLE www.acsami.org Electrodeposition in Capillaries: Bottom-up Micro- and Nanopatterning of Functional Materials on Conductive Substrates Antony George, A. Wouter Maijenburg, Michiel G. Maas, Dave H. A. Blank, and Johan E. ten Elshof * Inorganic Materials Science, MESA+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands b S Supporting Information ’ INTRODUCTION Fast and cost-effective realization of high resolution complex patterns of functional materials is crucial in future manufacturing technologies. Patterning techniques such as photolithography, 1,2 electron beam lithography, 3 ion beam lithography, 4 nanoimprint lithography, 5 and scanning probe lithographic methods 6,7 are used in industry and research for patterning functional materials. However, all these techniques require either cleanroom proces- sing conditions or the use of resist materials often with complex processing steps of wet/dry etching. Some of these methods are slow due to their serial nature. Well-known alternatives devel- oped by the Whitesides research group are the soft lithographic methods that use micro/nanopatterned polydimethylsiloxane (PDMS) molds and stamps in conformal contact with a substrate as a template for site-selective patterning with functional materials. 8 Interesting features of soft lithography are its techni- cal simplicity, low capital investment cost, and effectiveness in producing large-scale functional patterns of arbitrary materials. 8,9 The soft lithographic techniques can be divided into printing and molding-based methods and include microcontact printing, 10 micromolding in capillaries (MIMIC), 11 micromolding, 12,13 mi- crotransfer molding, 14 edge lithography, 15 solvent assisted micro-molding, 16 nanotransfer printing, 17 and gas phase pattern deposition. 18 These methods can be used for the fabrication of different functional patterns including self-assembling molecules, metals, metal oxides, nanoparticles, bio-molecules, and poly- meric materials. Electrodeposition is a simple, scalable, and cost effective tool for fabricating inorganic functional thin films of metals, 19,20 metal alloys, 21,22 metal oxides, 23 and conducting polymers 24 on conductive substrates. Electrodeposition using templates such as patterned photoresist, 1,2 polycarbonate membranes, 25 anodic alumina membranes, 26 colloidal crystals, 27 and self-assembled monolayers 19,28 attracted a lot of research and industrial interest due to its ability to fabricate 2D and 3D patterns of inorganic functional materials, 1,2,19 nanowires, 25,26 and nanotubes. 25 As is shown below, a combination of soft lithography and electro- deposition can be used as a tool for large area patterning of various functional materials on micrometer and nanometer scale. In comparison with other combinations of deposition and lithographic techniques to generate functional material patterns, the combination of electrodeposition and soft lithography is technically versatile and cost effective as it can be carried out under normal ambient conditions, without the use of complex patterning, etching, and deposition steps. In the present paper, we demonstrate the possibility of a single step, bottom-up, inexpensive, and easy process for 2D nano- and micropatterning of functional material on conductive substrates by electrodeposition using patterned PDMS molds as templates. A schematic diagram of the patterning process is shown in Figure 1. A PDMS mold with micrometer or nanometer scale channels is gently pressed against a conductive substrate. A con- nected channel structure is formed between the substrate and the PDMS mold. The substrateÀmold assembly is immersed in an electrolyte solution and used as working electrode to deposit functional materials like nickel, platinum, zinc oxide (ZnO), and Received: July 1, 2011 Accepted: August 12, 2011 ABSTRACT: A cost-effective and versatile methodology for bottom-up patterned growth of inorganic and metallic materials on the micro- and nanoscale is presented. Pulsed electrodeposition was employed to deposit arbitrary patterns of Ni, ZnO, and FeO(OH) of high quality, with lateral feature sizes down to 200À290 nm. The pattern was defined by an oxygen plasma-treated patterned PDMS mold in conformal contact with a conducting substrate and immersed in an electrolyte solution, so that the solid phases were deposited from the solution in the channels of the patterned mold. It is important that the distance between the entrance of the channels, and the location where deposition is needed, is kept limited. The as-formed patterns were characterized by high resolution scanning electron microscope, energy-dispersive X-ray analysis, atomic force microscopy, and X-ray diffraction. KEYWORDS: soft-lithography, oxides, electrodeposition, micropatterning