An atomic-resolution nanomechanical mass sensor

Mechanical resonators are widely used as inertial balances to detect small quantities of adsorbed mass through shifts in oscillation frequency1. Advances in lithography and materials synthesis have enabled the fabrication of nanoscale mechanical resonators2,3,4,5,6, which have been operated as precision force7, position8,9 and mass sensors10,11,12,13,14,15. Here we demonstrate a room-temperature, carbon-nanotube-based nanomechanical resonator with atomic mass resolution. This device is essentially a mass spectrometer with a mass sensitivity of 1.3 × 10−25 kg Hz−1/2 or, equivalently, 0.40 gold atoms Hz−1/2. Using this extreme mass sensitivity, we observe atomic mass shot noise, which is analogous to the electronic shot noise16,17 measured in many semiconductor experiments. Unlike traditional mass spectrometers, nanomechanical mass spectrometers do not require the potentially destructive ionization of the test sample, are more sensitive to large molecules, and could eventually be incorporated on a chip. Nanoscale mechanical resonators can make precision measurements of force, position and mass. Atomic resolution in mass sensing at room temperature has now been demonstrated with a carbon nanotube-based resonator that essentially operates as a mass spectrometer. The atomic equivalent of shot noise has also been detected.