Modeling of Self-Assembly Dynamics of Photolithographically Patterned MUFFINS Biosensor Arrays
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1002-N07-08
Modeling of Self-Assembly Dynamics of Photolithographically Patterned MUFFINS Biosensor Arrays Saul Lee, Peter Carmichael, Jason Meiring, Michael Dickey, Scott Grayson, Roger T. Bonnecaze, and C. Grant Willson Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712 ABSTRACT The ability to mass produce biosensor arrays at low costs is an important target for the diagnostics industry. Our group has previously explored the batch production of mesoscale sized hydrogels as platforms for biosensors using photolithographic techniques. The individual hydrogel features were self-assembled through lateral capillary interactions to form a closed packed configuration and the pre-polymer medium was subsequently UV-cured to form the array. To understand the self-assembly dynamics, we investigated, through simulation, the flotation behavior of two assembling particles and its dependence on physical constants such as surface tension and particle density. Simulation results revealed that the objects tilt toward each other as they came into proximity. The tilt angle decreased with increasing surface tension but increased with increasing particle density. Understanding the details of the flotation behavior is necessary in the development of a full scale self-assembly model. INTRODUCTION Biosensor arrays have become important diagnostic tools with applications in the medical and defense industries. A majority of current fabrication methods use spot deposition to affix detection probes onto glass slides. Although this leads to high information density and can be performed via automation, spot deposition is a sequential process. Methods for fabrication of detection probes in parallel and subsequently assembled into functional arrays could aid in the mass production of future biosensor arrays. Parallel batch fabrication was achieved using the MUFFINS (Mesoscale Unaddressed Functionalized Features INdexed by Shape) platform proposed by Meiring et al [1]. Individual hydrogel features were prepared by photolithographically patterning poly(ethylene glycol) diacrylate into desired shapes through a contact mask. Each feature contained a bioprobe (DNA) that was covalently cross-linked into the matrix. Large quantities of individual features could be produced separately and subsequently reassembled to form arrays. The assembly of hydrogel features entailed floating the MUFFINS on the surface of a pre-polymer solution. Features self-assembled through lateral capillary interactions to form a closed packed configuration. After the assembly, the surrounding pre-polymer solution was UVcured to set the array. The self-assembly of objects floating at an liquid-air interface has been studied extensively by Bowden et al [2] and Kralchevsky et al [3]. However, most of these efforts have focused on objects that are less dense than the liquid phase. The MUFFINS are denser than the pre-polymer liquid phase and form a wetting contact angle with the liquid. Both of the preceding arguments suggested that the objects shou
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