Thelen, MarcMarcThelenBochud, NicolasNicolasBochudBrinker, ManuelManuelBrinkerPrada, ClaireClairePradaHuber, PatrickPatrickHuber2021-07-152021-07-152021-06-14Nature Communications 12 (1): 3597 (2021-12-01)http://hdl.handle.net/11420/9896Nanoporosity in silicon leads to completely new functionalities of this mainstream semiconductor. A difficult to assess mechanics has however significantly limited its application in fields ranging from nanofluidics and biosensorics to drug delivery, energy storage and photonics. Here, we present a study on laser-excited elastic guided waves detected contactless and non-destructively in dry and liquid-infused single-crystalline porous silicon. These experiments reveal that the self-organised formation of 100 billions of parallel nanopores per square centimetre cross section results in a nearly isotropic elasticity perpendicular to the pore axes and an 80% effective stiffness reduction, altogether leading to significant deviations from the cubic anisotropy observed in bulk silicon. Our thorough assessment of the wafer-scale mechanics of nanoporous silicon provides the base for predictive applications in robust on-chip devices and evidences that recent breakthroughs in laser ultrasonics open up entirely new frontiers for in-situ, non-destructive mechanical characterisation of dry and liquid-functionalised porous materials.en2041-172320211Nature Publishing Group UKhttps://creativecommons.org/licenses/by/4.0/PhysikTechnikJournal Article10.15480/882.366010.1038/s41467-021-23398-010.15480/882.36603412765910.15480/336.3174Journal Article