quartzApril 30, 2015 — . . . Steven LeBoeuf, a mechanical engineer scientist and the co-founder of Valencell, a company that supplies biometric sensors to wearable companies such as Jabra and Scosche, tells Quartz that Reddit’s theory is correct. Apple, like many wearable manufacturers, uses sensors that beam green light toward the skin. It penetrates through the first few layers of skin and measures the rate of bloodflow in the capillaries sitting below the surface. Green light, however, is absorbed by the ink used in most tattoos. Read More