Button cells

They're called button cells, coin cells or watch batteries. By any name, these tiny, round [batteries:coins] pose a choking danger to small kids. And if a child succeeds in swallowing a button cell, the battery may short-circuit in the moist [esophageal:windpipes] environment, burning the tissue. A few thousand kids wind up in emergency rooms each year after swallowing a button battery.But a team of Harvard and M.I.T. researchers that [includes:conclude] prolific inventor Robert Langer thinks they have a partial solution: a protective coating. The [scientists:researchers] covered batteries with a material - technically a quantum-tunneling [composite:compund] - in which microparticles of conductive metal are suspended in an insulating layer. Under most circumstances, including inside of a child, the layer is nonconductive.But when the material is subjected to high pressure, the microparticles are squeezed close enough together to carry a current. One such pressurized [environment:atmosphere] is the typical battery compartment in a small device - you often have to force the battery into place.