Session: 11-01: Micro/Miniature Two-Phase Devices/ Systems

Paper Number: 132716

132716 - Pool Boiling of Silicon With Multi-Length Scale Surface Structures 

Abstract: 

Boiling heat transfer has been widely studied for cooling and other energy-related applications. The rapid development of nanotechnology has enabled the fabrication of various micronanostructures to enhance surface boiling, including the critical heat flux (CHF) and heat transfer coefficient (HTC) [1-4]. Here the CHF is the maximum heat flux achieved on a boiling surface. This phenomenon is characterized by the formation of a blanket of heat-blocking vapor on the surface. Currently, the studied surface structures include etched or deposited nanowires[5], etched pillars, etched channels or pores, coated nanostructures, and certain hierarchical structures [6]. Among these, Song et al. investigated three-tier hierarchal tube structures, which are tube clusters with tube cavities treated to have nano-blade surfaces, fabricated with expensive photolithography and etching techniques [7]. A <138% CHF enhancement was observed compared with the smooth surface counterpart. Chu et al. studied the relationship between the surface roughness of silicon with multiple pillars of random sizes, which is defined as the ratio of actual contact area to projected area; they showed a 160% CHF enhancement compared with a smooth silicon counterpart [8]. Kim et al. also investigated the relationship between the surface of silicon with a pillar array structure and they demonstrated a 310% enhancement of CHF by adjusting the surface roughness [9]. In these representative studies, the structure size and shape are often random. A systematic study is still lacking to fully address factors such as structure sizes, structure periodicity, and surface roughness. In this work, we have investigated the pool boiling behavior of multi-length scale patterns etched on plain bare silicon wafers, with varied feature sizes and surface treatment. Polystyrene nanosphere (PSNS) lithography will be utilized to fabricate periodic nano-/micro-pores and pillars across the silicon substrate [10]. The size and pitch of these self-assembled hexagonal nanosphere patterns can be modified, offering a flexible and multifunctional template for various applications [11, 12]. With the modification of etching time, one can control the pitch by altering the size of the nanospheres with the use of oxygen plasma reactive ion etching (RIE) [10]. The available range of nanosphere diameters extends from a maximum of 1 um down to a minimum of 50 nm. Furthermore, RIE will also be utilized to tune the nanoscale surface roughness of the fabricated structures. Our work will contribute to the understanding of pool boiling heat transfer mechanisms and will provide valuable insights for the design and optimization of multi-length scale patterns on bare silicon wafers. The insights gained from this research can be applied to various engineering applications requiring efficient thermal management, including electronics cooling, power generation, and renewable energy systems.

Presenting Author: Qing Hao University of Arizona

Presenting Author Biography: From Aug. 2011, he became an Assistant Professor in Aerospace and Mechanical Engineering at the University of Arizona. His research interest is nanoscale energy transport and its applications in advanced materials and nano-electronic devices. His current research efforts include heat transport inside Li-ion batteries, high-power electronics, boiling and condensation, thermal insulation materials, thermoelectrics, measurements and engineering applications of graphene and other two-dimensional materials. In 2015, he received the AFOSR YIP Award for graphene research. In 2017, he received NSF CAREER Award for thermal studies of grain boundaries. He was promoted to Associate Professor in May 2017. In 2020, he was awarded the Dean's Fellow from the College of Engineering.

Authors:

Fabian Medina The University of Arizona
Qing Hao University of Arizona
Haomin Li University of Arizona
Qiyu Chen University of Arizona