Stop flow lithography synthesis of non-spherical metal oxide particles

• Stop flow lithography enabled the synthesis of a library of non-spherical composite particles.
• SiO2 and Al2O3 shape analogues were realized through polymer burn-off and sintering.
• SEM confirmed the particle morphology.
• XRD analyses confirmed the composition and crystal structure of the ceramic particles.

Non-spherical micron and nano-sized particles and their composites have become essential in select application areas of optics, wear resistance, personnel protection, chemical mechanical polishing, and biomedicine. In this paper, the synthesis of composite and ceramic non-spherical particles using stop flow lithography is reported. Precursor suspensions of poly(ethylene glycol) diacrylate, 2-hydroxy-2-methylpropiophenone and SiO2 or Al2O3 are prepared. The precursor suspension flows through a microfluidic device mounted on an upright microscope and is polymerized in an automated process. A photomask patterned with transparent geometric features, which define the cross-sectional shapes of the particles, masks the UV light to synthesize micron sized particles. Particles with axial dimensions ranging from 35 to 167 μm were synthesized. Control of device channel depth and objective lens magnification enables the manipulation of the particle size. Composite particles in triangular, square, pentagonal, hexagonal, and circular cross sections were synthesized. Subsequently, the transformation of the composite particles into the corresponding metal oxide particles was achieved through polymer burn-off and sintering.

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