Phosphate buffer (PB) was prepared by mixing 10mM potassium phosphate monobasic solutions and 10mM potassium phosphate dibasic solutions to pH 8.5. To bind the second linker, glutaraldehyde, 5mL of filtered PB (FPB) with 50mg of sodium cyanoborohydride was mixed with 1mL of a 50% glutaraldehyde solution. The device was dipped in 160μL of the prepared solution for 1 hour and was consecutively rinsed with DIW.