Search for: All records

The boiling efficacy is intrinsically tethered to trade-offs between the desire for bubble nucleation and necessity of vapor removal. The solution to these competing demands requires the separation of bubble activity and liquid delivery, often achieved through surface engineering. In this study, we independently engineer bubble nucleation and departure mechanisms through the design of heterogeneous and segmented nanowires with dual wettability with the aim of pushing the limit of structure-enhanced boiling heat transfer performances. The demonstration of separating liquid and vapor pathways outperforms state-of-the-art hierarchical nanowires, in particular, at low heat flux regimes while maintaining equal performances at high heat fluxes. A deep-learning based computer vision framework realized the autonomous curation and extraction of hidden big data along with digitalized bubbles. The combined efforts of materials design, deep learning techniques, and data-driven approach shed light on the mechanistic relationship between vapor/liquid pathways, bubble statistics, and phase change performance. 

Polymer‐based materials hold great potential for use in thermoelectric applications but are limited by their poor electrical properties. Through a combination of solution‐shearing deposition and directionally applied solvent treatments, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films with metallic‐like conductivities can be obtained with high power factors in excess of 800 µW m⁻¹K⁻². X‐ray scattering and absorption data indicate that structural alignment of PEDOT chains and larger‐sized domains are responsible for the enhanced electrical conductivity. It is expected that further enhancements to the power factor can be obtained through device geometry and postdeposition solvent shearing optimization.

 

Capillary‐fed boiling of water from microporous metal surfaces is promising for low thermal resistance vapor chamber heat spreaders for hot spot management. Vapor transport through the void spaces in porous metals enables high heat fluxes at low evaporator superheat. In this work, the critical heat fluxes of capillary‐fed boiling in copper inverse opal (IO) wicks that consist of uniform pores with 3D periodicity is investigated. Template sintering is used to enlarge the “necks”, or hydraulic vias, that bridge adjacent IO pores of diameters from 0.6 to 2.1 µm. The enhanced neck size increases the hydraulic permeability for vapor extraction by an order of magnitude, and subsequently the CHF from 100 to 1100 W cm⁻². Modeling of the boiling limit accounts for the vapor pressure drop through an IO wick using Darcy's law at a given bubble departure rate. This work links the effect of wick structure design on the boiling crises phenomenon in microporous surfaces and demonstrates material capabilities for ultrathin and low superheat thermal management solutions for high‐power‐density electronic devices.