Extreme Nanoscale Thermal Insulation in Monolayer Nano Bubble Wraps

Thermal transport in the ultra–low-conductivity regime is central to advancing energy efficiency, thermal management, and emerging concepts in thermal computing. For decades,

aerogels have held the record for the lowest thermal conductivity under ambient conditions. Here, we introduce nano–bubble wrap materials that lower this benchmark by an additional

order of magnitude. These structures feature periodic 10 nm air cavities embedded within atomically thin monolayers, enabling simultaneous suppression of gas-phase conduction

through deep Knudsen confinement and reduction of solid-phase phonon transport via atomically thin walls, weak van der Waals coupling, and engineered strain. Time-domain

thermoreflectance measurements reveal remarkable low out-of-plane thermal conductivities below 0.001 W · M−1K−1 at room temperature and atmospheric pressure. Nano–bubble wraps offer a promising versatile platform for controlling heat flow in ultrathin materials, opening pathways for thermal metamaterials and next-generation energy-efficient technologies.