. (a) Schematic of the PMMA microfluidic chip. The bioreactor measured 40 mm ร— 100 ยตm ร— 100 ยตm and the solution of sample and matrix are loaded by syringe pumps. On the end of the bioreactor, coaxial tubes were sealed to mix digests with a matrix solution and to deposit onto a MALDI target plate (b) Assembled tryptic digest microfluidic chip: components including PMMA chip and cover slip, inlet and outlet connectors, capillary and stainless steel tube.