A common type of fuel cell is the polymer electrolyte fuel cell (PEFC), but to achieve stable electric current generation, issues include devising a structure that doesn't obstruct gas flow and removing the water that is generated by the chemical reaction of hydrogen and oxygen. To resolve those issues, problems must be detected by making measurements inside the cell. Mechanical engineers led by Kuniyasu Ogawa at Japan’s Keio University are developing new technology for measurement inside fuel cells. “A fuel cell is made of metal, and it's hard to measure inside metal objects using MRI. So, what we do in our lab is, we use very small coils, and obtain signals by inserting those coils into the fuel cell,” says Ogawa. Their technique is based on the nuclear magnetic resonance (NMR) method, and places lots of small planar coils, covered with an insulating film, inside a fuel cell. This has made it possible to measure conditions inside the cell in detail, quickly, at multiple points.