6cm polystyrene tissue culture dish

The device was fabricated on a commercial 6cm polystyrene tissue culture dish (Falcon). 11 holes of diameter 1.5mm were drilled at the dish bottom (Fig. S1, Step 1). A UV-curable adhesive was spread on the bottom surface using a sharp blade (NOA81, Norland Products, Fig. S1, step 2). A semi-permeable polycarbonate membrane (Whatman^® Nuclepore Track-Etched Membranes, pore diameter 0.1μm) was placed on the adhesive layer (Fig. S1, step 3). The device was cured under UV-light for 2 minutes (365nm 20W LED, Shenzen Yonton Opto). The membrane covered 9 drilled holes, thus leaving 2 holes uncovered, which will serve as inlets. A circular Polydimethylsiloxane (PDMS) stamp of 150μm thickness and 20 mm diameter was prepared using a metal mold of the same dimensions. The PDMS stamp was placed on a 24x24 mm² coverslip (Fig. S1, Step 4). The UV-curable adhesive was flown between the coverslip and PDMS by capillary, thus forming a spacer of thickness 150μm (Fig. S1, Step 5). The spacer was half-cured by UV-exposure, and the PDMS was pealed off (Fig. S1, Step 6).