EAGER: Nanoscale Elastocaloric Effect in Phase-Change Nanowires for Solid-State Cooling

University Of Texas At Dallas, Richardson TX

Investigators

Abstract

Currently, most cooling devices (refrigerators, air-conditioning units) employ environmentally-harmful fluids, known as refrigerants. They are also hard to miniaturize, preventing their implementation in electronic devices, which due to continued miniaturization and increase of processing power, necessitate novel cooling mechanisms for the semiconductor industry to keep progressing. The proposed research aims to investigate the nanoscale elastocaloric effect, a cooling mechanism where deformation causes an atomic-level change in a solid, which results in significant changes in its temperature. This effect promises to eliminate the need for harmful fluids used as refrigerants, and to be applicable both in miniaturized, cooling devices integrated inside electronic chips, and in consumer products such as self-cooling fabrics and smart coatings. Mentoring, research and outreach opportunities for graduate, undergraduate and K-12 students will also be enabled by this proposal. The graduate students will mentor undergraduates and high-school students hosted in the investigator’s lab. By doing meaningful research related to this project, they will be inspired to pursue careers in science and technology. The overall goal is to pioneer the exploration of the elastocaloric effect in nanoscale structures by assessing its promise in a model system: vanadium dioxide (VO2) nanowires. The proposed research is experimental and aims to directly characterize the effect’s output (temperature change) by infrared imaging, thus proving its existence in VO2. Similarly, measurements of the deformation of the nanowires as a function of temperature will provide metrics to put bounds on the magnitude of the effect in VO2, thus assessing the promise of the material for novel cooling devices, and the need for deeper investigations. Nanowires will be deposited in flexible substrates by self-assembly and microfluidic patterning methods, in order to align them in one direction and obtain a macroscale nanostructured film. These films will then be deformed along the alignment direction to trigger the elastocaloric effect. The resulting temperature changes will be measured using infrared imaging. Finally, using state-of-the-art nanomechanical testing, individual nanowires will be deformed in order to characterize their response at two representative temperatures, thereby quantifying bounds for the energetics of the phase transformation (i.e. its entropy change). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.