A poly(dimethyl siloxane) (PDMS, SILPOT 184, Dow Corning GmbH) mixture of 10:1 mass ratio 95 between base and curing agent was poured onto the silicon wafer, degassed in a vacuum chamber 96 and cured at 80 °C on a hot plate for at least 4 hours. After the PDMS is cured, peel it off carefully 97 and trim it into a proper shape. The inlets and the outlets of the microfluidic device were created 98 by punching through the PDMS block with a biopsy punch (φ = 0.75 mm).