Mapping Thermal Flow under the Skin.

Abstract

Galen, the ancient Greek physician, believed that the balance of the 4 humors within the body—blood, black bile, yellow bile, and phlegm—could determine the temperament and health of an individual. Hence, techniques such as bloodletting became routine practice. In introductory classes today, medical students giggle when they hear of such primitive medicine. But Hippocrates, Galen, and other humoralists were definitely right on one point—that we are highly individualistic (thus the growth of precision medicine), and possibly right on another—that how fluids flow within the body could indicate health and disease. Professor John Rogers, from the Department of Materials Science and Engineering at University of Illinois Urbana-Champaign, has invented a way to noninvasively and continuously measure blood flow across the body that could prove the second point. The journal spoke to him about his latest innovation. Rogers has developed skin-like patches that contain a heating element—an actuator—and an array of sensors that pick up the spread of thermal power. “The chemistry innovation is how you make sensors that are similar to skin itself,” says Rogers. Bernard Bulwer The devices (Fig. 1) are “super thin with low thermal mass,” according to Rogers. This gives the devices an insignificant thermal footprint. To effectively thermalcouple to sense small temperature variations under the skin, there must be “intimate physical contact between device elements and skin,” explains Rogers. Air gaps are no good, …