Electric Field Controlled Electrospray Deposition for Precise Particle Pattern and Cell Pattern Formation Jingwei Xie, Alireza Rezvanpour, and Chi-Hwa Wang Dept. of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576 Jinsong Hua Institute of High Performance Computing, 1 Fusionopolis Way, 16-16 Connexis, Singapore 138632, Singapore DOI 10.1002/aic.12198 Published online February 3, 2010 in Wiley Online Library (wileyonlinelibrary.com). Photolithography, soft lithography, and ink jetting have been used for automated micropattern fabrication. However, most of the methods for microfabrication of surface pattern are limited to the investigation of material properties of substrates with high-cost and complex procedures. In the present study, we show a simple (single-step) yet versa- tile and robust approach to generate biodegradable polymeric particle patterns on a sub- strate using electrospray deposition through a mask. Various particle patterns including patterned dots, circles, squares, and bands can be easily formed and the features of parti- cle patterns could also be tailored using different masks and electrostatic focusing effects. Furthermore, cell patterns can be achieved on the surface of particle patterns by blocking the areas without particle deposition on the substrate and culturing cells on the substrate. Polymeric particle patterns and cell patterns developed in this study could be used in the high throughput screening of sustained release formulations, cell-based sens- ing, and drug discovery. In addition to experimental results, an analysis of the associated electric field is used to investigate quantitatively the nature of focusing effect. Scaling analysis is also applied to obtain the dominate terms in electrospray deposition process. V V C 2010 American Institute of Chemical Engineers AIChE J, 56: 2607–2621, 2010 Keywords: electrospray, deposition, focusing effect, particle pattern, cell pattern, scaling analysis Introduction The microarray and micropattern technologies have attracted tremendous interests among researchers owing to their wide applications in the fields of optics, biotechnology, electronics, medical and clinical diagnosis, disease finger printing, drug screening, targeting and evaluation, toxicity assessment, signal transduction study, and cancer treatment development. 1–3 Microfabrication techniques including pho- tolithography, soft lithography, and ink jetting have been widely used for automated micropattern fabrication. 2,3 The details of surface engineering approaches to achieve micro- pattern surfaces can be referred to the review work by Geiss- ler and Xia. 4 However, most of the methods for microfabri- cation of surface pattern are limited to material properties of substrates, high cost, and complex procedures. Cell pattern- ing is also an important tool for organizing cells on trans- ducers for cell-based sensing and cell-based drug discovery. 5 In addition, controlling cellular microenvironment using micropatterning may be used in directing cell fate for tissue engineering applications. 6 Cell patterning approaches can also be used to study fundamentals of cell biology such as Correspondence concerning this article should be addressed to C.-H. Wang at chewch@nus.edu.sg. V V C 2010 American Institute of Chemical Engineers AIChE Journal 2607 October 2010 Vol. 56, No. 10