Toward practical mass spectrometry with nanomechanical pillar resonators by surface acoustic wave transduction

Nanoelectromechanical systems (NEMS) have shown outstanding performance in the detection of small masses down to single proton sensitivity. To obtain a high enough throughput for application in practical mass spectrometry, NEMS resonators are arranged in two-dimensional (2D) arrays. However, all state-of-the-art electromechanical transduction methods rely on electrical lines placed close to the mechanical resonators, which drastically restricts the density of 2D resonator arrays. An exception is the transduction by surface acoustic waves (SAWs), which has so far only been shown for the transduction of single nanomechanical pillar resonators. Here, we demonstrate the transduction of pillar pairs by SAWs. The pillars have a diameter of 700 nm and show a mass responsivity of −588 ± 98 ng ⁻¹. The distances between the pillar pairs are 70 nm and 14.3 µm. SAW transduction enabled us to measure both pillars of each pair with electrical lines no closer than 300 µm, illustrating the potential of SAWs to transduce dense arrays of pillar resonators, a crucial step toward practical mass spectrometry with NEMS.