Thermal Management with Graphene-Ag Nanocubes Heterostructures

The main purpose of textiles throughout history is to regulate heat flow and provide warmth or decrease excessive heat for the wearer. In recent times, the textile industry has developed new materials that can ensure the wearer stays dry in hot environments and that repel moisture. The main downside of these new textiles, however, is that their electromagnetic response has not been fully optimized, allowing too much radiation to be absorbed and radiated back to the skin, causing the wearer to overheat. Our work is composed of two parts: simulation and experimentation. Simulations will first be conducted to better understand the thermal metamaterial consisting of a heterostructure with metallic nanoparticles, graphene, , and SU-8 spin coated onto silicon wafers.<br/>Starting with theoretical modeling, we considered first a heterostructure made of Ag nanoparticles, graphene, FeCl₃ on silicon. When the FeCl₃ layer is thin, around 50 nm, the absorbance between 3 mm and 12 mm is around 2%, independent of the number of graphene layers. Such heterostructures could be useful for thermal management systems.<br/>For FeCl₃ layer thickness of 1.2 mm or larger, it is possible to tune the absorbance resonance peaks of localized acoustic graphene plasmons (AGPs) in graphene by means of a gate voltage in the mid-IR regime, with absorbance reaching almost 100%. Such heterostructures are useful for cooling the textiles with respect to the 3 K temperature of outer space.<br/>The positions of the localized AGPs resonance peaks can be tuned in the range between 3 mm and 12 mm by means of a gate voltage.<br/>After realizing that FeCl₃ undergo strong oxidation, we replaced FeCl₃ by SU-8, resulting in high-quality SU-8 layers. Based on the simulation results, we have been fine tuning the recipe for spin coating the graphene ink on SU-8. We have also been fine-tuning the recipe to spin coat Ag nanoparticles onto graphene. The fabricated heterostructures made of Ag nanocubes/graphene/SU-8/Si wafer will be characterized in terms of refractive index, reflectivity, absorption, profilometry, FTIR, and ellipsometry.<br/>Then, we replace the Si wafer by gold-coated Si wafers. The gold layer serves as a mirror for the Fabry-Perot cavity. The full heterostructure is placed on a hot plate and a thermocouple. The hot plate is heated up to 38 C to simulate the body temperature and standoff is created between heterostructures and the hot plate. Thermocouples will be used to measure the temperature difference between the heterostructures and gold mirrors to see if the heterostructures have a significant effect on the thermal management property.