Coating with PEM. The devices consisting of 3 layers of PEMs (PLL-PSS-PLL, PLL-PSS-PLL-FITC, PAH-PSS-PAH, PLL-PSS-PLL-OEG(25%)) were prepared using layer-by-layer deposition. PLL and PSS solutions were transferred (0.5 g L -1 in water) into glass syringes and mounted on low-pressure pumps. CETONI Elements software was used to program low-pressure pumps in the PEM deposition experiments. The first layer was coated by transferring PLL solution onto a freshly oxygen-plasmaactivated channel. The device was rinsed using water to remove unreacted species. The second and third layers were deposited using PSS solution without any further activation steps. For details, see Supplementary Information 6.3.