Multidimensional Generation of Combinatorial Organic Arrays by Selective Wetting Inscription By Yu-Jin Na, Sang-Wook Lee, Wonsuk Choi, Sung-Jin Kim, and Sin-Doo Lee* The potential of solution-processed organic materials for use in electronic and optoelectronic systems is mainly due to their excellent processing capability on a variety of substrates. [1–3] In developing combinatorial systems, [1] one of the critical issues is how to precisely register disparate elements from different solutions on a single substrate in a lateral or stackable manner. Progress has been made towards the registration of such disparate elements at a 2D level by direct patterning methods, including soft lithography, [4–6] ink-jet printing, [7–9] and laser- induced thermal imaging. [10,11] However, due to blurs and errors in the lateral definition of the element patterns generated by those methods, a new patterning and integration technology with high precision in 2D and 3D is required for producing high- performance combinatorial arrays. Recently, a substrate pattern- ing method creating wetting contrast patterns for solutions was demonstrated to fabricate organic thin-film transistors [12] and electronic circuits [13] through solution casting. This method relies on the surface modification of a substrate into different morphologies or self-assembled patterns by physical or chemical methods such as UV light exposure or microcontact printing. This type of surface modification would not be applicable for producing heterogeneous elements in a 3D array or even laterally in a 2D array. We report the development of a highly parallel and accurate platform for the fabrication of multidimensional heterogeneous arrays in a pattern-by-pattern (2D) or a pattern-on-pattern (3D) fashion. Our concept lies primarily in the control of the selective wettability on a commanding layer (CL) by laser-assisted inscription within the framework of the wetting transition. [14] This selective-wetting inscription (SWI) on the CL provides precise self-registration of heterogeneous elements in 2D as well as in 3D, with high levels of functionality for successive patterns. Our SWI scheme is shown in Figure 1A. For one class of element patterns, the unit process consists of the following three steps: i) a CL of a hydrophobic material showing a wetting transition is first formed on a substrate in solution; ii) selective-wetting (or dewetting) regions are generated through a predefined photo- mask by laser-assisted SWI on the CL; iii) element patterns of an COMMUNICATION www.advmat.de Figure 1. A) Schematic illustration of fabrication of multidimensional, heterogeneous organic arrays by SWI. The unit process can be simply repeated to selectively integrate different classes of organic elements on a single substrate. The 2D fabrication and 3D fabrication processes are depicted in the left and in the right, respectively. B) Contact angle of xylene dissolving the green light-emitting polymer (LEP) on the CL. The thickness of the CL, d, was varied with the coating velocity and the CL concentration. The critical thickness of the CL is denoted by d c , at which a wetting transition occurs. [*] Prof. S.-D. Lee, Y.-J. Na, S.-W. Lee, W. Choi School of Electrical Engineering, Seoul National University Seoul 151-600 (Republic of Korea) E-mail: sidlee@plaza.snu.ac.kr Dr. S.-J. Kim Department of Electrical Engineering, Columbia University New York, NY 10027 (USA) DOI: 10.1002/adma.200801288 Adv. Mater. 2009, 21, 537–540 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 537