Single-particle Mass Spectrometry with arrays of frequency-addressed nanomechanical resonators

Abstract

One of the main challenges to overcome to perform nanomechanical Mass Spectrometry (NEMS-MS) analysis in a practical time frame stems from the size mismatch between the analyte beam and the extremely small nanomechanical detector area. We report here the demonstration of NEMS-MS with arrays of 20 individually addressed nanomechanical resonators where the number of inputs-outputs for the whole array is the same as that of a single resonator. While all resonators within an array are interconnected via two metal levels, each resonator is designed with a distinct resonance frequency which becomes its individual address. In order to perform single-particle Mass Spectrometry, the resonance frequencies of the two first modes of each NEMS within an array are monitored simultaneously. Using such an array, mass spectra of metallic aggregates in the MDa range are acquired with more than one order of magnitude improvement in analysis time due to the increase in capture cross section compared to individual resonators. A 20 NEMS array is probed in 150ms with the same mass limit of detection as a single resonator. Spectra acquired with a conventional Time- of-Flight (TOF) mass spectrometer in the same system show excellent agreement. As individual information for each resonator within the array is retained, the array becomes a particle imager, each resonator acting as a pixel. With this technique, we demonstrate how Mass Spectrometry Imaging (MSI) at the single particle level becomes possible by mapping a 4cm-particle beam in the MDa range and above.