The microchip includes 12 parallel channels (width: 1 mm, height: 100 μm), which merge into a single port E (elution) of a 0.3 mm diameter. At the other end of each channel, similar ports S (sample) are created by punching the PDMS, and a compressed small cotton wool (< 1 μg) serving as a frit for retaining the chromatographic particles is pressed down to the bottom of the port (Fig. 1a) using a metal rod.