Chemical Temperature Control

Abstract

Exothermic and/or endothermic chemical reactions in combination with phase change materials can produce output temperature(s) within strict tolerances without requiring expensive and complicated external equipment to generate and maintain an output temperature. Similarly, an exothermic phase change material, which generates heat as a consequence of crystallizing a supercooled liquid, can generate heat at a constant temperature, without requiring expensive and complicated external equipment, as a consequence of the liquid form of the exothermic phase change material being in equilibrium with the solid form of the exothermic phase change material. Numerous biological and chemical processes and/or diagnostic devices require a constant temperature or temperatures for set periods of time. An example completely non-instrumented diagnostic platform based on nucleic acid amplification is described, which is particularly suited for use in developing countries that may not have access to expensive and complicated external equipment.

1 . An assay platform, comprising:
 a zone requiring controlled temperature conditions; and   a heating element thermally coupled to the zone requiring controlled temperature conditions,   the heating element comprising:
 an exothermic chemical reagent mixture; and 
 a phase change material; 
   wherein the amount of phase change material is configured to provide a controlled, substantially constant temperature to the zone requiring controlled temperature conditions by at least a partial phase transition of the phase change material when heated by an exothermic chemical reaction generated by the exothermic chemical reagent mixture.   
     
     
         2 . The assay platform of  claim 1 , wherein said exothermic chemical reagent mixture comprises iron powder and carbon powder. 
     
     
         3 . The assay platform of  claim 1 , wherein said exothermic chemical reagent mixture comprises a reduction of copper with magnesium. 
     
     
         4 . The assay platform of  claim 1 , wherein said exothermic chemical reagent mixture comprises calcium oxide hydration. 
     
     
         5 . The assay platform of  claim 1 , wherein said phase change material comprises a paraffin. 
     
     
         6 . The assay platform of  claim 1 , wherein said phase change material is selected from the group consisting of a metal, an inorganic compound, an inorganic eutectic and an organic compound. 
     
     
         7 . The assay platform of  claim 1 , wherein said zone requiring controlled temperature conditions comprises a zone for conducting a biochemical reaction requiring a constant, elevated temperature. 
     
     
         8 . The assay platform of  claim 7 , wherein said biochemical reaction is a nucleic acid amplification reaction. 
     
     
         9 . The assay platform of  claim 8 , wherein said nucleic acid amplification reaction is an isothermal nucleic acid amplification. 
     
     
         10 . The assay platform of  claim 7 , wherein said biochemical reaction is a reverse-transcription reaction. 
     
     
         11 . The assay platform of  claim 1 , wherein said zone requiring controlled temperature conditions comprises a zone for a biological organism requiring incubation at elevated, constant temperature. 
     
     
         12 . The assay platform of  claim 1 , wherein said heating element has a well-defined working temperature. 
     
     
         13 . The assay platform of  claim 12 , wherein said well-defined working temperature is between about 53 to about 70 degrees C. 
     
     
         14 . The assay platform of  claim 1 , wherein said heating element has a well-defined working duration, after which the temperature of the heating element drops back to ambient levels. 
     
     
         15 . The assay platform of  claim 14 , wherein said well-defined working duration is approximately one hour. 
     
     
         16 . The assay platform of  claim 1 , further comprising a second heating element, wherein said second heating element has a different working temperature or duration, resulting in an assay platform having multiple heating plateaus. 
     
     
         17 . The assay platform of  claim 16 , wherein said platform generates two heating plateaus. 
     
     
         18 . The assay platform of  claim 17 , wherein said platform generates a first heating plateau comprising a working temperature between about 92 to about 96 degrees C. for approximately 5 minutes, followed by a second heating plateau comprising a working temperature between about 53 to about 70 degrees C. for approximately 80 minutes. 
     
     
         19 . The assay platform of  claim 1 , further comprising a density-driven closed-loop fluid circulation channel configured to achieve heat cycling in a circulation fluid as a function of the circulation fluid being heated as it passes through the heating element, and cooled when it is outside the heating element. 
     
     
         20 . The assay platform of  claim 19  wherein said heating element acts as a heat source and an area outside of said heating element acts as a heat sink; wherein said heat source is at a lower elevation than said heat sink; and wherein said closed-loop fluid circulation channel has a minimally tortuous fluid path. 
     
     
         21 . The assay platform of  claim 17 , further comprising a chemical cooling element. 
     
     
         22 . The assay platform of  claim 1 , further comprising a wicking-driven linear channel configured to achieve heat cycling in a circulation fluid as a function of the circulation fluid being heated as it passes repeatedly over the heating element and being cooled when it is outside the heating element. 
     
     
         23 . The assay platform of  claim 1 , farther comprising a spring-loaded, syringe-like pump driven linear channel configured to achieve heat cycling in a circulation fluid as a function of the circulation fluid being heated as it passes repeatedly over the heating element and being cooled when it is outside the heating element. 
     
     
         24 - 46 . (canceled) 
     
     
         47 . The assay platform of  claim 12 , wherein said well-defined working temperature is between about 37 to about 55 degrees C. 
     
     
         48 . The assay platform of  claim 1 , wherein said phase change material transitions from a liquid to a gas when heated by said exothermic chemical reaction. 
     
     
         49 . The assay platform of  claim 1 , wherein said phase change material transitions from a solid to a liquid when heated by said exothermic chemical reaction. 
     
     
         50 . The assay platform of  claim 1 , wherein said heating element is in one layer. 
     
     
         51 . The assay platform of  claim 1 , wherein said heating element is in two layers. 
     
     
         52 . The assay platform of  claim 51 , wherein said phase change material is disposed between the zone requiring controlled temperature conditions and the exothermic chemical reagent mixture. 
     
     
         53 . The assay platform of  claim 1 , wherein said phase change material is carbohydrate encapsulated. 
     
     
         54 . The assay platform of  claim 53 , wherein said phase change material is encapsulated in carbohydrate spheres. 
     
     
         55 . The assay platform of  claim 1 , wherein said heating mixture is configured to maintain a constant temperature without using an electrical power source. 
     
     
         56 . The assay platform of  claim 1 , wherein said exothermic chemical reagent mixture comprises magnesium.