Biomedical Engineering Society Conference Proceedings – October 2008 1 Performance Consistency of Layer‐by‐Layer Nanoassembly Techniques Melanie Groan † , Juan Lopez † , Mark DeCoster ‡* , Steven A. Jones ‡ † Louisiana Tech Biomedical Engineering Ph.D. Program, ‡ Department of Biomedical Engineering, * Institute of Micromanufacturing Louisiana Tech University, Ruston, LA Layer‐by‐layer (LbL) nanoassembly is a process rapidly growing in popularity for the development of nano‐scale thin films in a wide‐ranging set of biomedical applications (1). Despite this high praise for LbL, problems endemic to the manufacturing process can lead to variability in surface roughness, and often require complex layer structures to provide a viable substrate for the active final layer (1, 2). This variability has not been well studied, but is evidenced in the literature, and in the work in our laboratory. We have examined examples that state specific guidelines for time, temperature, colloid concentrations, and pH and noted variability in found protocols that is indicative of the current lack of standardization.. Adsorption times range from hours to a few minutes, and seem to be as driven by individual laboratory practices as by established guidelines. Emerging technologies such as the Nano eNabler (BioForce) which can lay down patterns in atto‐ and femtoliter volumes for single spots at the rate of several hundred nanometers per second may be able to lower the variability in surface roughness. Microfluidic Flow Cell Arrays (MFCA), when coupled with a stricter control of solution and buffers, may also improve LbL results by finely controlling exposure times for each subsequent layer on an assembly. Overall, automated methods of generating nano‐ and micro‐scale assemblies for biomedical research promise to reduce the variability between experimental sets. Introduction Two devices available at our institution that can provide surface coatings on the nanometer thickness scale are LbL and eNabler. Little data exists quantitatively comparing the performance of these methods. We evaluated three kinds of eNabler surfaces: no substrate, single substrate, and patterned LbL substrate. For the LbL test segments, we used two kinds of LbL assemblies: we replicated the LbL substrate layers from our patterned LbL and generated a multilayer surface commonly used in platelet adhesion experiments in our laboratory. Methods Various surfaces were generated using both eNabler methods and standard LbL methods. For all surface configurations, a top layer of FITC‐laced poly‐L‐Lysine (FITC‐PLL) was used as our fluorescent surface. The relative intensities were used to compare top layer structures generated by the various methods. The more FITC‐PLL that fixed itself to a surface, the brighter the fluorescence for any particular surface. This indicator allowed for a quantitative comparison of surface efficiency and structure. The polyions used for various substrate layers were poly(diallyldimethylammonium chloride), PDDA, and Polystyrene Sulfonate Sodium Salt, PSS. Nano eNabler Patterned LbL The eNabler surfaces were printed in three sets of thirty 15 mm diameter dots, each set being two rows of 15 as displayed in Figure 1. The three sets are identified by a series of dots forming numbers, printed at the same time as each set but not included in the data processing. For set 1, FITC‐PLL was printed directly onto the glass slide, then dried at 60°C, where all subsequent drying processes were performed at this temperature. This process is the standard protocol in the laboratory for generating eNabler patterns. The LbL structure