Full Electrostatic Control of Nanomechanical Buckling

Buckling at the micro and nanoscale generates distant bistable states which can be beneficial for sensing, shape-reconfiguration and mechanical computation applications. Although different approaches have been developed to access buckling at small scales, such as the use heating or pre-stressing beams, very little attention has been paid so far to dynamically and precisely control all the critical bifurcation parameters, the compressive stress and the lateral force on the beam. Precise and on-demand generation of compressive stress on individually addressable microstructures is especially critical for morphologically reconfigurable devices. Here, we develop an all-electrostatic architecture to control the compressive force, as well as the direction and amount of buckling, without significant heat generation on micro/nano structures. With this architecture, we demonstrated fundamental aspects of device function and dynamics. By applying voltages at any of the digital electronics standards, we have controlled the direction of buckling. Lateral deflections as large as 12% of the beam length were achieved. By modulating the compressive stress and lateral electrostatic force acting on the beam, we tuned the potential energy barrier between the post-bifurcation stable states and characterized snap-through transitions between these states. The proposed architecture opens avenues for further studies that can enable efficient actuators and multiplexed shape-shifting devices

Nanomechanical Measurement of the Brownian Force Noise in a Viscous Liquid

Accepted manuscrip

Nonlinear nanomechanical mass spectrometry at the single-nanoparticle level

Nanoelectromechanical systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. As nanoscale objects land on NEMS sensors one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset of nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture with which to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and verified the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about 500 single-particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures that possess a limited dynamic range

Performance of nano-electromechanical systems as nanoparticle position sensors

Nanoelectromechanical systems (NEMS) have been utilized as sensitive mass sensors in many applications such as single cell characterization, volatile organic biomarker detection and single molecule mass spectrometry. Using the frequency shift detection, mass of single analytes can be resolved. Mass detection sensitivity can be further improved by accurate measurement of the position, unlocking extra capabilities in nanoscale positioning and manipulation applications. Here, we studied the position sensing performance of two-mode NEMS resonators during detection of single 20 nm gold nanoparticles (GNPs). By recording the position of each particle with frequency shift sensing, the position detection accuracy was evaluated for different beam models and the results are validated by SEM imaging our results indicate that the position sensing accuracy, and therefore the mass sensing accuracy, of nanomechanical resonators depends critically on the use of appropriate beam models

Vapor sensing of colorectal cancer biomarkers in isolation by bare and functionalized nanoelectromechanical sensors

Small dimensions and high resonance frequencies render Nanoelectromechanical systems (NEMS) sensitive mass detectors. Mass detection capability can be used to sense chemicals in the gas phase by functionalizing the device, usually with a polymeric film. The performance of NEMS-based gas detectors in breath analysis applications depends crucially on the selectivity between selected functionalization layers and targeted biomarkers. Here, we report the detection of four colorectal cancer biomarkers at parts-per-million concentration levels, when introduced in isolation to the sensor system within a dry nitrogen stream. The biomarkers, 3-methylpentane, cyclohexane, nonanal, and decanal, were then discriminated from each other by using the combined response of three NEMS devices: one bare device, and two devices coated with either poly(ethyleneoxide) or poly(caprolactone). Our results indicate that bare NEMS are more responsive to high molar mass biomarkers, whereas functionalized sensors are more responsive toward more volatile biomarkers. Considering the inherently fast response times and minuscule limits of detection of NEMS devices, the combined response of differentially coated sensors can be used as the main sensing element to identify and distinguish cancer biomarkers in human breath