They are called button cells, coin cells or watch batteries. By any names, this tiny round batteries pose a choking danger to kids. And if a kid succeeds in swallowing a button cell, the battery may shortcircut in a moist suffergea environment, burning the tissue. A few children wind up in the emergency room each year after swalowing a button battery. But a team of Harvard MIT researchers that include prolific inventor Robert Lancer think they have a partial solution, a protective coating. The scientists covered the battery with a material, technically a quatine composite, in which micorparticles of conductive metal are suspended in a insulating layer. Under most circumstances, including inside a child, the layers are non-conductive, but  when the materials are subjected to high pressure, the microparticles are squized together enough to carry currents. One such pressurized environment is the typical 

battery compartment in a small device. You often have to force the battery into place. So the same battery that remains inlert when swallowed works just fine when it's jammed into its slot in a hearing aid. The waterproof design would prevent batteries from corrosion and high humidity. The research is in the proceedings of the Natural Academy of Sciences. Tests with  pigs found the coated battery to be gentle on a porsigned surfugus. Next step figure out a way to keep the kids from putting  batteries into their mouth in the first place. Can a quantin  composite  be made to taste terrible? Thanks for the minute. This is Scientists American sixty seconds.