Digital Microfluidic Chip for Rapid Portable Detection of Mercury(II)

This paper reports a rapid and visual detection of mercury ion on a new developed digital microfluidic chip with electrostatic manipulated droplets, which employed a principle of conjugated polymers and label-free oligonucleotides for mercury ion detection. The complex of water-soluble conjugated polymer, poly (3-(3^´ -N,N,N-triethylamino-1^´ -pro-pyloxy)-4-methyl-2,5-thiophene hydrochloride) (PMNT) and a label-free, mercury-specific oligonucleotide (MSO) probe is used as a mercury detector. While the detector droplet is fixed on the microfluidic chip, the target mercury ionic droplet is transported to the detector and then mixed together by electrostatic force driving, resulting in the color of the detector changing from red to yellow. We demonstrate that the detection system is portable and highly selective, and it can identify micromolar Hg²⁺ concentrations within minutes with the naked eye.