Since fingerprint scanners first appeared on smartphones in 2011 they’ve become pretty much a standard feature. They’re fast, convenient, and relatively secure, since fingerprints are unique enough that the odds of anyone having a similar enough print to unlock your phone are very low, unless someone cares enough to design a convincing duplicate of your fingerprint. There’s not just one type, though: some scanners rely on light, others on electricity, and still others on sound to map the ridges and valleys of your fingers. Capacitive (electronic sensors) are popular in smartphones because they’re accurate, small, and fast, but optical and ultrasonic… Read more