The Rogers Research Group at the University of Illinois at Urbana-Champaign have expanded on their flexible skin sensor technology to measure blood flow in vessels 1 to 2 millimeters under the skin. Current methods to measure blood flow in a clinical setting rely on optical imaging techniques that require patients to remain still for the duration of the measurement. The skin sensor, which attaches to the skin like a temporary tattoo, would enable blood flow measurement over 24 hours as the patient moves through daily life.
The device is composed of Ti/Cu/Ti/Au sensing/heating elements carried on a silicone substrate (Ecoflex) approximately 40 µm thick. Once attached to the skin, the sensor remains in place through van der Waals forces between the skin and the sensor’s silicone substrate. The sensor is a thermal transducer that is composed of a circular thermal actuator and two concentric rings of sensors. The central actuator heats the surrounding skin (3.5 mW mm-2), providing a controlled, background temperature. The concentric rings of sensors collect temperature data, which is used to create a temperature distribution map. Temperature distribution and thermal flow data is translated to blood flow rate via computer algorithms.
The device was tested on human wrist veins during movement and motionless tasks. Before the device can be used clinically, researchers need to develop an independent power source and a method to wirelessly transmit the thermal data. The clinical applications of the device include monitoring near-surface blood vessels.
(hat tip: IEEE Spectrum)