A conformable device to measure subdermal fluid flow comprising: a substrate, wherein the substrate is soft, stretchable and flexible; a thermal actuator supported by the substrate; an upstream temperature sensor supported by the substrate; a downstream temperature sensor supported by the substrate, wherein the upstream and downstream temperature sensors (120;130) are opposibly positioned relative to the thermal actuator to measure with the upstream temperature sensor an upstream temperature from the thermal actuator, and to measure with the downstream temperature sensor a downstream temperature from the thermal actuator; an actuator reference sensor supported by the substrate, wherein the actuator reference sensor is separated from a notional line connecting the upstream and downstream temperature sensors (120; 130) by a reference sensor separation distance to measure effects of the actuator independent of flow in a conduit underlying the conformable device during use; an ambient reference sensor supported by the substrate, wherein the ambient reference sensor is separated from the notional line connecting the upstream and downstream temperature sensors (120; 130) by an ambient reference sensor separation distance that is sufficiently large so that an ambient reference sensor reading is substantially independent of thermal actuation state, wherein the ambient reference sensor separation distance is between about 10 mm and 20 mm; a microprocessor in electronic communication with the actuator reference sensor, the ambient reference sensor, and the downstream and upstream temperature sensors (120; 130) configured to calculate subdermal fluid flow in the conduit from the measured upstream and downstream temperatures. a substrate, wherein the substrate is soft, stretchable and flexible; a thermal actuator supported by the substrate; an upstream temperature sensor supported by the substrate; a downstream temperature sensor supported by the substrate, wherein the upstream and downstream temperature sensors (120;130) are opposibly positioned relative to the thermal actuator to measure with the upstream temperature sensor an upstream temperature from the thermal actuator, and to measure with the downstream temperature sensor a downstream temperature from the thermal actuator; an actuator reference sensor supported by the substrate, wherein the actuator reference sensor is separated from a notional line connecting the upstream and downstream temperature sensors (120; 130) by a reference sensor separation distance to measure effects of the actuator independent of flow in a conduit underlying the conformable device during use; an ambient reference sensor supported by the substrate, wherein the ambient reference sensor is separated from the notional line connecting the upstream and downstream temperature sensors (120; 130) by an ambient reference sensor separation distance that is sufficiently large so that an ambient reference sensor reading is substantially independent of thermal actuation state, wherein the ambient reference sensor separation distance is between about 10 mm and 20 mm; a microprocessor in electronic communication with the actuator reference sensor, the ambient reference sensor, and the downstream and upstream temperature sensors (120; 130) configured to calculate subdermal fluid flow in the conduit from the measured upstream and downstream temperatures.