Oil Microsealing: A Robust Micro‐compartmentalization Method for On‐Chip Chemical and Biological Assays

A simple and robust method to compartmentalize aqueous solutions into an array of independent microchambers is presented. The array of microchambers fabricated in poly(dimethylsiloxane) are filled with the sample solution through a microfluidic channel and then sealed with oil to isolate the microchambers from each other. A water reservoir close to the microchambers allows the maintainance and incubation of sub‐nanoliter solutions (e.g., at 37 °C) within the chambers for hours without any problem of evaporation. Once assembled, the device is self‐sustainable and can be used for different application purposes. As a demonstration, the device configuration is shown to be suitable for spatiotemporal control of the inner solution conditions by light stimulation through a photomask. This method was applied for the generation of regular EmGFP (emerald green fluorescent protein) expression arrays, selective photobleaching, photopatterning of calcium concentration, and cell culture in independent microchambers.