Single-Particle Nanomechanical Mass Spectrometry in Nanoliter Liquid Suspensions

The mass of nanoparticles critically affects their behavior and functional performance, creating a demand for tools that combine high-throughput, high-resolution single-particle analysis with minimal sample consumption. Dip-in nanomechanical probes address this need by transferring analytes directly to nanowire resonators, requiring only nanoliters of suspension and minimizing sample losses. Employing ionic liquids as media enables the use of a microscopic droplet as stable sample reservoir, and vacuum operation for enhanced mass resolution. Tests with 30 nm gold nanoparticles achieve accurate mass characterization in 15 minutes, with probe resolution of 0.1 ag, wetting fluctuations reduced to 1 ag, and negligible sample consumption. These results highlight the potential of dip-in probes for fast, precise single-particle mass analysis across a broad range of nanoparticle sizes.