A rainbow patch that reads your heartbeatResearchers at the Norwegian University of Science and Technology (NTNU) have built a small transparent patch that looks like the back of a CD and, paired with an ordinary smartphone camera, can measure pulse and blood vessel stiffness. Medical Design & Development, which republished the university's story on October 30, calls it the first of its kind. The patch is silicone rubber with no electronics or cables.How it worksOne side carries a nanoscale pat...