BDD growth was then realized using microwave plasma chemical vapor deposition process. The deposition conditions are detailed in the Experimental part. Taking into account the low fusion temperature of the fiberglasses, a lowplasma densitywas used.Moreover, these conditions provide a higher mean free path of the active species and allow higher depth growth. SEM images of some fibers of the diamond membrane are sketched in Fig. 1c and d. These pictures illustrate diamond layer thickness according to the membrane depth. One can see that diamond covered 300 μm of the 350 μm thick pristine fiberglass filter, see Fig. 2b. Since there is no plasma within the membrane during the growth step, only diffusion through its pores is responsible for the diamond formation. After 8 h of growth, the thickness of the diamond layer varies from 250 nm for the upstream fibers and 40 nm for downstreamones (Fig. 2c, d and e). This difference is due to the concentration gradient of the species according to the distance fromthe surface of the membrane. Nevertheless, despite this thickness gradient across the filter, themembrane is fully coveredwith diamond and can be easily handled without any particular precautions. One can note that efficient coating in the membrane thickness can only be achieved through BDD growths. It clearly suggests that carbonated species involved in diamond growth are created from trimethylboron.