**5.1 Fabrication and the test of the multiscale micro/nanostructured wick structure**

The wick structure of the asymmetric vapor chamber with a nanostructured superhydrophobic condenser, which is described in the previous section, is nanostructured by a chemical surface modification method presented in Section 3.1. The bare sintered wick structure shown in **Figure 16(a)** is coated with a layer of a thin-fin array of copper oxide, which is shown in **Figure 16(b)** and **(c)**. The thermal performance of the vapor chamber with a bare sintered wick structure is compared with that with a multiscale micro/nanostructured wick structure. The experimental setup is the same as described in Section 4.1. The uncertainties of vertical and horizontal thermal resistance for these vapor chambers are 0.7% and 0.8%, respectively.

#### **Figure 16.**

*Scanning electron microscope (SEM) images of the wick structures of the asymmetric vapor chamber with a nanostructured superhydrophobic condenser: (a) bare sintered powder wick structure; (b) low-magnification of multiscale micro/nanostructured wick structure; and (c) high-magnification of multiscale micro/ nanostructured wick structure [29].*

#### *Heat Exchangers*

Moreover, the thermal performance of the ultrathin vapor chamber case 1, which only has a copper-covered stainless-steel mesh wick structure (shown in **Figure 9(a)**, is compared with that of vapor chamber case 2, which has a multiscale micro/nanostructured wick structure (shown in **Figure 9(b)**). The fabrications of other parts of these two types of vapor chambers can be found in sections 3.1 and 4.1. The parameters for assessing the thermal performance can be found in sections 3.2 and 4.1.
