Epidermal Devices for Analysis of Temperature and Thermal Transport Characteristics

Abstract

Provided are tissue-mounted devices and methods for monitoring a thermal transport property (e.g., thermal conductivity, thermal diffusivity, heat capacity) of tissue, such as skin. The devices conformally mount to the tissue and have one or more thermal actuators and a plurality of sensors. The actuator applies heat to the tissue and the sensors to detect a spatio temporal distribution of a physiological tissue parameter or physical property resulting from the heating. This spatio temporal information may be correlated with a rate, velocity and/or direction of blood flow, the presence of a vascular occlusion, circulation changes due to inflammation, hydration level and other physiological parameters.

1 - 86 . (canceled) 
     
     
         87 . A system for non-invasively monitoring a blood flow parameter, the system comprising:
 a thermal flow device configured to be applied to the surface of skin, the thermal flow device comprising a flexible substrate, a thermal actuator and a plurality of thermal sensors, wherein the thermal sensors are arranged at distinct angular positions and two distinct distances relative to a center of the thermal actuator; and   a computing device, the computing device comprising a memory and one or more computer processors, the memory comprising instructions that when executed by the one or more computer processors cause the one or more computer processors to:
 activate the thermal actuator; 
 during the activation, record temperature data from one or more of the thermal sensors; and 
 determine a blood flow parameter based at least in part on the temperature data. 
   
     
     
         88 . The system of  claim 87 , wherein the thermal flow device conforms intimately to the surface without an externally applied pressure. 
     
     
         89 . The system of  claim 87 , further comprising an adhesive between the flexible substrate and the surface of the skin. 
     
     
         90 . The system of  claim 87 , wherein the thermal actuator comprises an area of at least about 4 mm 2 . 
     
     
         91 . The system of  claim 87 , wherein power applied to the thermal actuator for activation is between 0.1 mW/mm 2  and 50 mW/mm 2 . 
     
     
         92 . The system of  claim 87 , wherein the distinct angular locations of the temperature sensors are at least 45 degrees apart relative to the center of the thermal actuator. 
     
     
         93 . The system of  claim 87 , wherein determining a blood flow rate parameter includes determining one or more parameters for converting the temperature data to blood flow velocity. 
     
     
         94 . The system of  claim 87 , wherein determining a blood flow rate parameter includes determining a rate of temperature increase of at least one temperature sensor. 
     
     
         95 . The system of  claim 87 , wherein determining a blood flow rate parameter includes determining a temperature increase of the thermal actuator. 
     
     
         96 . The system of  claim 87 , wherein the thermal sensors are arranged as two concentric rings of sensors relative to the thermal actuator, with a first ring separated from the actuator by a first of the two distinct distances and a second ring separated from the actuator by a second of the two distinct distances. 
     
     
         97 . A method of non-invasively monitoring a blood flow parameter, the method comprising:
 contacting a thermal flow device to a surface of skin, the thermal flow device comprising a flexible substrate, a thermal actuator and a plurality of thermal sensors, wherein the thermal sensors are arranged at distinct angular locations and at least two distinct distances relative to a center of the thermal actuator;   activating the thermal actuator;   during the activation, recording temperature data from one or more of the thermal sensors; and   determining a blood flow parameter based at least in part on the temperature data.   
     
     
         98 . The method of  claim 97 , wherein the thermal flow device conforms intimately to the surface without an externally applied pressure. 
     
     
         99 . The method of  claim 97 , further comprising an adhesive between the flexible substrate and the surface of the skin. 
     
     
         100 . The method of  claim 97 , wherein the thermal actuator comprises an area of at least about 4 mm 2 . 
     
     
         101 . The method of  claim 97 , wherein power applied to the thermal actuator for activation is between 0.1 mW/mm 2  and 50 mW/mm 2 . 
     
     
         102 . The method of  claim 97 , wherein the distinct angular locations of the temperature sensors are at least 45 degrees apart relative to the center of the thermal actuator. 
     
     
         103 . The method of  claim 97 , wherein determining a blood flow rate parameter includes determining one or more parameters for converting the temperature data to blood flow velocity. 
     
     
         104 . The method of  claim 97 , wherein determining a blood flow rate parameter includes determining a rate of temperature increase of at least one temperature sensor. 
     
     
         105 . The method of  claim 97 , wherein determining a blood flow rate parameter includes determining a temperature increase of the thermal actuator. 
     
     
         106 . A system for non-invasively monitoring a blood flow parameter, the system comprising:
 a thermal flow device configured to be applied to the surface of skin, the thermal flow device comprising a flexible substrate, a thermal actuator, a first temperature sensor co-located with the thermal actuator and second temperature sensor spaced apart from the thermal actuator; and   a computing device, the computing device comprising a memory and one or more computer processors, the memory comprising instructions that when executed by the one or more computer processors cause the one or more computer processors to:
 activate the thermal actuator; 
 during the activation, record temperature data from one or more of the thermal sensors; and 
 determine a blood flow parameter based at least in part on the temperature data.