PDMS microfluidic film for in vitro engineering of mesoscale neuronal networks

Polydimethylsiloxane (PDMS) microfluidic devices have become a standard tool for engineering cells and multicellular networks in vitro. However, the reservoirs, or through-holes where cells access the devices, are usually fabricated manually using a biopsy punch, making it difficult to create a large-scale array of small (<1 mm) reservoirs. Here, we present a fabrication process for a thin-film microfluidic device, or a microfluidic film ({\mu}FF), containing an array of through-holes. Holes as small as 100 {\mu}m by 100 {\mu}m spanning 10 mm by 10 mm are characterized. The geometry of the through-holes was precisely defined by the photoresist mould. A challenge in using the {\mu}FF for cell culture was air-bubble entrapments in the through-holes, which became more prominent with smaller holes. We show that this issue can be overcome using ethanol-mediated wetting of the PDMS surface, and demonstrate functional recording of cultured neuronal networks grown in {\mu}FFs. This technology opens new application of microfluidic devices to mesoscale systems comprised of several tens to hundreds of cells.