One-step pipetting of barcoded planar microparticles into compact monolayer assembling chip for efficient readout of multiplexed immunoassay

Barcoded planar microparticles have many qualities suitable for developing cost-efficient multiplexed immunoassays. But at the translational research level, there are a number of technical aspects yet remain to be addressed which includes robustness and efficiency of the assay readout process. Assay readout process involves automated barcode identification and signal intensity values from each planar microparticle. For this, each microparticle has to be correctly aligned for correct barcode readout while being, ideally, compactly assembled for maximum microparticle imaging efficiency. To simultaneously achieve such alignment and assembly of microparticles but in a straightforward manner, we designed a microfluidic microparticle assembling chip that only requires a single pipetting step. Our design utilizes capillary flow based guided particle assembly, which allows maximum microparticle-based immunoassay readout efficiency. With the aid of image processing algorithms, we obtained good multiplex immunoassay readout accuracy similar to conventional imaging platforms. Our approach is applicable to both soft elastomer materials (e.g. PDMS) and rigid materials (e.g. polystyrene), the latter of which is frequently used for injection molding based mass production. We anticipate our device could help developing facile and user-friendly platform technologies based on barcoded planar microparticles. ### Competing Interest Statement The authors have declared no competing interest.