Pool Boiling Heat Transfer on Directly 3D-Printed Metallic Micropillars on Silicon Chips

This study investigates pool boiling heat transfer on metallic micropillar arrays fabricated directly onto silicon wafers using laser powder bed fusion (LPBF). A two-step deposition strategy was employed, in which a thin Sn-3Ag interlayer was printed to enhance metallurgical bonding and thermal compatibility, followed by the fabrication of AISi10Mg micropillars. The working fluid was TMC-49, tested at atmospheric pressure on both a bare silicon wafer and the LPBF-fabricated micropillar surface. High-speed imaging revealed that the bare silicon exhibited sparse nucleation at low heat fluxes, rapid bubble coalescence, and early vapor blanketing near CHF <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\sim 85\text{kW}/\mathrm{m}^{2})$</tex>, whereas the micropillar surface maintained uniform nucleation, rapid bubble departure, and continuous liquid rewetting up to CHF (−379 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{kW}/\mathrm{m}^{2})$</tex>. This represents a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4.5\times$</tex> enhancement in CHF. The micropillar surface also exhibited <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{a} &gt; 7\times$</tex> improvement in peak heat transfer coefficient (HTC), reaching <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 11.9 \text{kW}/\mathrm{m}^{2}\mathrm{K}$</tex> compared to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 1.6\text{kW}/\mathrm{m}^{2}\kappa$</tex> for the plain wafer. These gains are attributed to increased nucleation site density, capillary-driven liquid replenishment through inter-pillar channels, increased stability in vapor venting, and additional surface roughness from LPBF-sintered particles that augment surface area and promote microlayer evaporation. The results demonstrate that LPBF offers a scalable alternative to traditional microfabrication methods, enabling high-performance boiling surfaces without complex cleanroom processing.