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In this study, we investigate the effects of micron-scale surface patterns on the alignment of individual cells and groups of cells. Using a simple replication molding process we produce a number of micron-scale periodic wavy patterns with different pitch and depth. We observe C2C12 cells as they grow to confluence on these patterns and find that, for some geometries, cell-cell interaction leads to global alignment in a confluent culture when individual cells would not align on the same pattern. Three types of alignment behavior are thus defined: no alignment, immediate alignment, and alignment upon confluence. To further characterize this response, we introduce a non-dimensional parameter that describes the aligning power of a periodic pattern based on its geometry. The three types of alignment behavior can be distinguished by the value of the alignment parameter, and we identify values at which the transitions in alignment behavior occur. Applying this parameter to data from the current and several earlier studies reveals that the parameter successfully describes substrate aligning power over a wide range of length scales for both wavy and grooved features.

In this study, the effectiveness of analytical models which attempt to predict the density of unsintered powder metallurgy (PM) compacts as a function of consolidation pressure is investigated. These models do not incorporate the nonuniform densification of powder compacts and may insufficiently describe the pressure/densification process. Fabrication of uniform and nonuniform Zinc (Zn) tablets is conducted to assess the validity of the pressure/density model developed by Quadrini et al. (Quadrini and Squeo, 2008, “Density Measurement of Powder Metallurgy Compacts by Means of Small Indentation,” J. Manuf. Sci. Eng., 130(3), pp. 0345031–0345034). Different tablet properties were obtained by varying the compaction pressure and fabrication protocol. Density gradients within Zn tablets result in a spatial dependence of Vickers microhardness (HV) throughout the fabricated specimen. As a result, micro-indentation testing is used extensively in this study as a characterization tool to evaluate the degree of nonuniformity in fabricated Zn tablets. Scanning electron microscopy (SEM) is also employed to verify tablet density by visual examination of surface porosity as compaction pressure is varied and sintering is applied.