Morphology of C$_{60}$ crystals synthesized in microfluidic space

Since their initial discovery in 1985, Fullerene C$_{60}$ has attracted significant attention for their unique physical and chemical properties. In terms of technological issues, fabricating C$_{60}$ crystals with complex shapes for practical uses is a very important challenge. Recently, the liquid/liquid interfacial precipitation method for the synthesis of needle-like C$_{60}$ nanowhisker crystals was reported. However, the bulk structures of these C$_{60}$ crystals were all uniform and were single-dimensional. Here, we report unusual structures of C$_{60}$ crystals including tubes, trees, branches, hollow-ended columns, multiple pods, short prisms, and needles synthesized in a microfluidic device using a simple liquid/liquid interfacial precipitation method. The C$_{60}$ crystal morphology is categorized mainly by temperature, and is similar to the morphology of snow crystals. This simple method yields complex geometries of C$_{60}$ crystals quickly, and could be applied to all materials synthesis techniques that use liquid/liquid interfacial precipitation.