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Nanosphere lithography (NSL) is a bottom‐up, self‐assembly approach that enables rapid, low‐cost patterning of nanoscale features. The practical application and scalability of NSL relies on the ability to achieve defect‐free nanosphere self‐assembly over large substrate areas. Self‐assembly methods for single‐layer nanosphere templates are typically evaluated using scanning electron microscopy (SEM) imaging, with literature reports focusing on maximum area of continuous nanosphere coverage. An alternative performance metric—namely, the percentage of nanospheres exhibiting perfect hexagonal close‐packing (%HCP)—is uniquely critical to NSL precision and repeatability. To enhance current methods of evaluating nanosphere self‐assembly, this work presents an SEM image analysis approach for rapidly quantifying packing defects in single‐layer nanospheres to determine %HCP. The method uses variations in SEM edge effect brightness to distinguish spheres with perfect packing from those in defect configurations or along edges. Comparison of image analysis program results with manual counting of nanospheres indicates that the program has a high degree of accuracy, with a mean error on the %HCP metric of +8.6% (absolute error). The results suggest that the present strategy offers a promising pathway to rapid evaluation of nanosphere self‐assembly for high‐precision NSL applications such as surface‐enhanced Raman scattering, photovoltaic cells, and nanogap electrodes.

 

In situ direct laser writing ( is DLW) strategies that facilitate the printing of three-dimensional (3D) nanostructured components directly inside of, and fully sealed to, enclosed microchannels are uniquely suited for manufacturing geometrically complex microfluidic technologies. Recent efforts have demonstrated the benefits of using micromolding and bonding protocols for is DLW; however, the reliance on polydimethylsiloxane (PDMS) leads to limited fluidic sealing ( e.g. , operational pressures <50–75 kPa) and poor compatibility with standard organic solvent-based developers. To bypass these issues, here we explore the use of cyclic olefin polymer (COP) as an enabling microchannel material for is DLW by investigating three fundamental classes of microfluidic systems corresponding to increasing degrees of sophistication: (i) “2.5D” functionally static fluidic barriers (10–100 μm in height), which supported uncompromised structure-to-channel sealing under applied input pressures of up to 500 kPa; (ii) 3D static interwoven microvessel-inspired structures (inner diameters < 10 μm) that exhibited effective isolation of distinct fluorescently labelled microfluidic flow streams; and (iii) 3D dynamically actuated microfluidic transistors, which comprised bellowed sealing elements (wall thickness = 500 nm) that could be actively deformed via an applied gate pressure to fully obstruct source-to-drain fluid flow. In combination, these results suggest that COP-based is DLW offers a promising pathway to wide-ranging fluidic applications that demand significant architectural versatility at submicron scales with invariable sealing integrity, such as for biomimetic organ-on-a-chip systems and integrated microfluidic circuits.