Time-Resolved Mass Sensing of a Molecular Adsorbate Nonuniformly Distributed Along a Nanomechnical String

Abstract

We show that the particular distribution of mass deposited on the surface of a nanomechanical resonator can be estimated by tracking the evolution of the device's resonance frequencies during the process of desorption. The technique, which relies on analytical models we have developed for the multimodal response of the system, enables mass sensing at much higher levels of accuracy than is typically achieved with a single frequencyshift measurement and no rigorous knowledge of the mass profile. We report on a series of demonstration experiments, in which the explosive molecule 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) is vapor deposited along the length of a silicon nitride nanostring to create a dense, random covering of RDX crystallites on the surface. In some cases, the deposition is biased to produce distributions with a slight excess or deficit of mass at the string midpoint. The added mass is then allowed to sublimate away under vacuum conditions, with the device returning to its original state over about 4 h (and the resonance frequencies, measured via optical interferometry, relaxing back to their pre-mass-deposition values). Our claim is that the detailed time trace of observed frequency shifts is rich in information-not only about the quantity of RDX initially deposited but also about its spatial arrangement along the nanostring. The data also reveal that sublimation in this case follows a nontrivial rate law, consistent with mass loss occurring at the exposed surface area of the RDX crystallites. arXiv:1501.05647v2 [cond-mat.mes-hall]

Graphene nano-electromechanical mass sensor with high resolution at room temperature

“…Figure 4 and Table S2 summarize the relation between the mass M res of a resonator and its minimum detectable mass δ m , as determined from literature data. 10 , 12 , 15 , 16 , 17 , 31 , 48 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 Most results have the fractional frequency fluctuation in the range of 10 −4 –10 −6 , with the solid trendlines in the figure indicating a mass resolution proportional to the resonator mass. The figure shows that identifying molecules in the mass range of MDa, which is a challenge in MS, can relatively easily performed with NEMS mass sensors, and furthermore, protein analysis and identification at single-molecule level is achievable if the resonator mass and the frequency fluctuation can be minimized sufficiently.…”

Exceptional Point Enhances Sensitivity of Optomechanical Mass Sensors

“…This is not the case neither for electromechanical nor single optomechanical mass sensors aforementioned, where the sensing process employs tracking the frequency shifts of the mechanical resonator due to mass changes induced by any added tiny object [1,2]. Moreover, simple multimodal response of a mechanical resonator enables mass sensing at much higher levels of accuracy than what is typically achieved with a single frequency shift measurement [15]. It goes without saying that mass sensor performances are enhanced in coupled systems that feature strong coupling regime or those exhibiting very narrow splitting in their eigenmodes structure.…”

Intermodal Coupling as a Probe for Detecting Nanomechanical Modes

“…Nanomechanical resonators have been used in a wide range of demanding sensor applications such as gas sensing [1][2][3], single-molecule mass sensing [4], single-protein [5] and neutral-particle [6] mass spectrometry, force sensing [7,8], and inertial imaging [9]. A common trend in recent years has been the exploitation of higher-order modes of a mechanical sensor in mass [5,6,[10][11][12][13][14][15], force [7,8,16], stiffness [13,17], and spatial sensing [9,18,19] where the extra information obtained from the higher-order modes usually expands the types of measurements and increases the sensitivity at the same time [20,21]. Higher-order modes can be utilized for numerous applications, such as quality factor control [22], mechanical vibration registers [23], or phonon cavities [24,25].…”