Microscale screen printing of large-area arrays of microparticles for the fabrication of photonic structures and for optical sorting

There are a limited number of methods applicable to the large-scale fabrication of arrays of discrete microparticles; however, such methods can be applied to the fabrication of structures applicable to photonics, barcoding, and optoelectronics. This manuscript describes a universal method, "microparticle screen printing" (μSP), for the rational patterning of micron-scale particles onto a variety of 2D substrates with diverse mechanical and chemical properties. Specifically, an array of microparticles of different sizes and compositions were patterned onto an array of materials of varying chemistry and stiffness using μSP yielding a diversity of homo/heterogeneous microparticle-based structures. Further, this manuscript reports how the Young's moduli of the substrate can be used to calculate contact area and thus interaction energies (quantified using Hamaker constants) between the particle/substrate during μSP. Generally, μSP is most effective for substrates with low Young's moduli and large Hamaker constants (A₁₃₂) with the target particles, as confirmed by the performance (quantified using yield and accuracy metrics) of μSP for the different empirically investigated particle/substrate combinations. These understandings allow for the design of optimal surface/particle pairing for μSP and were applied to the fabrication of a diversity of heterogeneous structures, including those with periodic vacancies in HCP (hexagonally closed packed) 2D photonic crystal useful to structural optics, optical particle screening useful to chemical assays, and the fabrication of structural barcodes useful for labeling and anticounterfeiting.