Ultrathin aluminum wick with dual-scale microgrooves for enhanced capillary performance

Abstract

With the burgeoning development of electronic devices with higher heat flux, thinner volume, lighter weight, and flexibility, heat pipes and vapor chambers are facing big challenges, especially in fabricating high-performance wicks within limited space. Microgrooves have gained increasing interest for the ability to be directly curved on the substrates, whereas the capillary performance enhancement hits a bottleneck. In this study, a chemical-free ultrathin aluminum wick with dual-scale microgrooves was fabricated via two-step laser texturing in 0.3 mm thick AA6061. The resultant surface, composed of main microgrooves and periodic sub-microgrooves in the ridges and valleys, demonstrated enhanced capillary performance via capillary rise rate experiments. The interaction of liquids in dual-scale microgrooves, that was the pumping effect and the flow resistance reducing effect, would be the main reason for the capillary performance enhancement. The ultrathin aluminum wick with dual-scale microgrooves exhibited a K/Reff about 1.322 µm with a shallow depth of about 100 µm, increased by 11.3% compared with that of single-scale microgrooves due to the assistance of the sub-microgrooves. This wick kept the ability to transport liquid under bending angles of 90 and 135°. Moreover, the wicking performance of different liquids decreased with the decrease of surface tension to viscosity ratio. The ultrathin aluminum wick with dual-scale microgrooves showed enhanced capillary performance, which was among the best with thickness less than 200 µm to our knowledge. This work provides insight into the design of high-performance wicks within limited space and weight.