A hybrid microfluidic-vacuum platform for interfacing with Petri dish. (A) Schematic design of the microfluidic device that show separate vacuum and fluidic channels. Side reservoirs (purple) contain buffer while buffer with FITC-Dextran (green) filled the middle reservoir. Parallel laminar flows from the three reservoirs generate stable gradients by diffusion. (B) Gradients of varying slope and profile generated in a single device. Two different gradient profiles generated at 0.5 mm and 6 mm downstream of the junction were visualized by FITC-Dextran profile. Gradient profiles were generated using 1 μl/min withdrawal rate. Experimentally measured and calculated gradient profiles were normalized for comparison. Scale bars are 100 μm.