With an aging infrastructure, the United States faces more scenarios like Flint, Michigan, where high lead levels became a threat to safety. Safa Amiri, a chemistry professor at the University of Florida, has developed a handheld water-quality sensor that detects contaminants with just a few drops of water. Learning to play the violin as a child, Safa says, helped him learn how to persevere. His model was his father, a successful entrepreneur in Iran.