Stable thermochromic polymer films with vanadium dioxide nanowires

Abstract

A thermochromic device includes a film and a number of vanadium dioxide nanowires disposed within the film. Each of the number of vanadium dioxide nanowires may have an aspect ratio between 10 and 500. The vanadium dioxide nanowires may have a length between 1 micrometer and 10 micrometers. The vanadium dioxide nanowires may have a non-conducting to conductor phase change temperature between 20 degrees Celsius and 60 degrees Celsius.

What is claimed is: 
     
         1 . A thermochromic device, comprising:
 a film; and   a plurality of vanadium dioxide nanowires disposed within the film, wherein each of the plurality of vanadium dioxide nanowires has an aspect ratio between 10 and 500.   
     
     
         2 . The thermochromic device of  claim 1 , wherein each of the plurality of vanadium dioxide nanowires has a diameter between 20 nanometers and 100 nanometers. 
     
     
         3 . The thermochromic device of  claim 1 , wherein each of the plurality of vanadium dioxide nanowires has a length between 1 micrometer and 10 micrometers. 
     
     
         4 . The thermochromic device of  claim 1 , wherein each of the plurality of vanadium dioxide nanowires has a non-conducting to conductor phase change temperature between 20 degrees Celsius and 60 degrees Celsius. 
     
     
         5 . The thermochromic device of  claim 1 , wherein the plurality of vanadium dioxide nanowires is disposed within the film to form a vanadium dioxide composite film. 
     
     
         6 . The thermochromic device of  claim 1 , wherein the vanadium dioxide composite film has a fill factor between 0.01 and 0.5. 
     
     
         7 . The thermochromic device of  claim 1 , wherein each of the plurality of vanadium dioxide nanowires comprises a core of vanadium dioxide and a shell of at least one selected from a group containing silicon dioxide, silicon nitride, titanium dioxide, and titanium nitride. 
     
     
         8 . The thermochromic device of  claim 7 , where each of the plurality of vanadium dioxide nanowires further comprises:
 a surface functionalization layer disposed on the shell and that renders each of the plurality of vanadium dioxide nanowires hydrophobic.   
     
     
         9 . The thermochromic device of  claim 1 , wherein a length of each of the plurality of vanadium dioxide nanowires is substantially aligned with a predetermined direction. 
     
     
         10 . The thermochromic device of  claim 9 , wherein the length of each of the plurality of vanadium dioxide nanowires is substantially aligned with the predetermined direction by applying an electric field. 
     
     
         11 . A method of controlling heating, comprising:
 receiving, with a plurality of vanadium dioxide nanowires, infrared radiation from a first side of a film;   transmitting, with the plurality of vanadium dioxide nanowires, the received infrared radiation to a second side of the film in response to receiving the infrared radiation;   transitioning, with the plurality of vanadium dioxide nanowires, a phase of the plurality of vanadium dioxide nanowires from a non-conducting phase to a conducting phase in response to an ambient temperature increasing above a phase transition temperature of the vanadium dioxide nanowires; and   reflecting, with the plurality of vanadium dioxide nanowires, the received infrared radiation to the first side of the film in response to the phase transition.   
     
     
         12 . The method of  claim 11 , wherein the phrase transition temperature is between 20 degrees Celsius and 60 degrees Celsius. 
     
     
         13 . A method of manufacturing a film, comprising:
 hot extruding a material comprising a polymer and a plurality of vanadium dioxide nanowires on a drum to form a rough film.   
     
     
         14 . The method of  claim 13 , further comprising:
 drawing the rough film along a plurality of rollers along a length of the rough film to form a finished film.   
     
     
         15 . The method of  claim 14 , further comprising:
 orienting each of the plurality of vanadium dioxide nanowires along a length of the finished film.   
     
     
         16 . The method of  claim 15 , wherein each of the plurality of vanadium dioxide nanowires is oriented by applying an electric field along the length of the finished film. 
     
     
         17 . The method of  claim 15 , wherein each of the plurality of vanadium dioxide nanowires is oriented by applying a tension along the length of the finished film. 
     
     
         18 . The method of  claim 14 , further comprising:
 orienting each of the plurality of vanadium dioxide nanowires along a width of the finished film.   
     
     
         19 . The method of  claim 18 , wherein each of the plurality of vanadium dioxide nanowires is oriented by applying an electric field along the width of the finished film. 
     
     
         20 . The method of  claim 18 , wherein each of the plurality of vanadium dioxide nanowires is oriented by applying a tension along the width of the finished film.