After losing his grandmother to Cancer when he was 10, Justin Hanes vowed to combat the disease. Now a chemical engineer, he has already won his first battle, designing polymer aerosols that deliver drugs to the lungs. Inhaling medications spares patients from injections, and certain drugs are more effective when breathed in. Hanes and his coworkers devised a way to make coated polymer particles porous; the particles serve as drug-carrying vessels that are large enough to lower the odds of attack by the immune system, but light enough to stay aloft and reach deep inside the lungs. There the polymer degrades, releasing insulin, growth hormones, or asthma medications over hours, days or weeks. Hanes and his colleagues’ pioneering work provided the core technology for Advanced Inhalation Research, founded in Cambridge, MA, in 1997 and sold two years later for $114 million. Although Hanes received stock from the sale, he chose an academic career. Now an assistant professor at John Hopkins University, he is building a new polymer for transporting cancer drugs. Enzymes secreted by growing tumors destroy the new polymer, thus discharging drugs where they’re needed most. “Why spread poison over the whole yard to eliminate one weed?” Hanes asks.