Acoustofluidic bubble-driven assisted functionalized nano-array coated micro pin-fins surface for efficient liquid-vapor phase change chip cooling

Embedded phase change boiling heat transfer is crucial for addressing the energy saving posed by high-power compact electronic devices. However, the endeavor to fabricate improved heat transfer structures in confined and constricted spaces remains a formidable challenge. Herein, we present a simple and straightforward acoustofluidics strategy to create stable, controllable, and efficient functional Zinc oxide (ZnO) nanoarray coatings in narrow micro-pin-fins chip surfaces with excellent phase change cooling performance. A robust acoustic micromixer combining bubble acoustic streaming and hydrodynamic effect provided by spiral microchannels is proposed to facilitate microscale fluid mixing across a broad flow rate range. The ZnO nanoarray-coated micro pin-fins chip, which allows for customizable lengths, densities, diameter, and morphology, is fabricated through straightforward adjustment of acoustofluidics micromixer parameters. Excellent phase change cooling performance is obtained on this surface, giving priority to nucleation (superheat≈ 4 °C, reduced by 50.2 %), low wall temperature (≤70.7 ℃) under the limit CHF, negligible pumping energy (≤3.5 kPa), and simultaneously enhancing the critical heat flux (CHF, from 45.1 to 77.2 W·cm⁻²) and heat transfer coefficient (HTC, from 5955 to 15552 W·m⁻²·K⁻¹) by up to 71.3 % and 161.1 %, respectively, compared with the smooth chip surface. In situ observation and analysis of the dynamic wetting behavior and boiling bubble dynamics indicated ZnO nanoarray coated micro pin-fins chip promotes the phase change heat exchange process by massive nucleation sites, effective control of boiling bubbles, and ultra-fast two-stage liquid rewetting capability. These findings not only provide important guidelines for the precise control and rational design of functional nanomaterials, but also provide new insights for embedded cooling and significant energy savings on power devices.