A fingerprint blurring phenomenon on a hierarchical nanoporous layer (HNL) glass has been discovered and experimentally investigated. The HNL glass was prepared by a simple one-pot etching as reported by the authors. IR absorption spectra and water contact angle revealed that the blurring does not come from a chemical decomposition but a transportation of the fingerprint components, and the capillary action drives the transportation, not the thermal diffusion. The fine pores in the HNL was indicated to develop the strong capillary force to blur the fingerprint. The fingerprint blurring phenomenon on the HNL can be a candidate for the third anti-fingerprint methodology after the popular ones of low frictional surfaces and anti-glare surfaces.

A hierarchical nanoporous layer (HNL) can be formed on the silicate glass surface by simple alkali etching. Though it reportedly exhibits various useful functions, such as superhydrophilicity, optical anti-reflection, and material impregnation, the principle of its formation still remains unclear. In this study, HNL formation behavior was experimentally investigated while using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) to clarify the role of boron contained in glass. As a result, it was found that HNL formation was significantly promoted by boron, which was rapidly eluted prior to alkali and alkaline earth metals. This suggests that boron, which forms the skeleton structure of glass together with Si and O, elutes to partially decompose the skeleton, and extends the elution route for HNL formation.