23 research outputs found
Atmospheric Pressure Mass Spectrometry by Single-Mode Nanoelectromechanical Systems
Weighing particles above MegaDalton mass range has been a persistent
challenge in commercial mass spectrometry. Recently, nanoelectromechanical
systems-based mass spectrometry (NEMS-MS) has shown remarkable performance in
this mass range, especially with the advance of performing mass spectrometry
under entirely atmospheric conditions. This advance reduces the overall
complexity and cost, while improving the limit of detection. However, this
technique required the tracking of two mechanical modes, and the accurate
knowledge of mode shapes which may deviate from their ideal values especially
due to air damping. Here, we used a NEMS architecture with a central platform,
which enables the calculation of mass by single mode measurements. Experiments
were conducted using polystyrene and gold nanoparticles to demonstrate the
successful acquisition of mass spectra using a single mode, with improved areal
capture efficiency. This advance represents a step forward in NEMS-MS, bringing
it closer to becoming a practical application for mass sensing of
nanoparticles.Comment: 24 pages, 4 figure
Design and fabrication of CSWAP gate based on nano-electromechanical systems
In order to reduce undesired heat dissipation, reversible logic offers a promising solution where the erasure of information can be avoided to overcome the Landauer limit. Among the reversible logic gates, Fredkin (CSWAP) gate can be used to compute any Boolean function in a reversible manner. To realize reversible computation gates, Nano-electromechanical Systems (NEMS) offer a viable platform, since NEMS can be produced en masse using microfabrication technology and controlled electronically at high-speeds. In this work-in-progress paper, design and fabrication of a NEMS-based implementation of a CSWAP gate is presented. In the design, the binary information is stored by the buckling direction of nanomechanical beams and CSWAP operation is accomplished through a mechanism which can selectively allow/block the forces from input stages to the output stages. The gate design is realized by fabricating NEMS devices on a Silicon-on-Insulator substrate. © Springer International Publishing Switzerland 2016
Three-Dimensional Electrode Integration with Microwave Sensors for Precise Microparticle Detection in Microfluidics
Microwave sensors integrated with microfluidic platforms can provide the size
and permittivity of single cells and microparticles. Amongst the microwave
sensor topologies, the planar arrangement of electrodes is a popular choice
owing to the ease of fabrication. Unfortunately, planar electrodes generate a
non-uniform electric field which causes the responsivity of the sensor to
depend on the vertical position of a microparticle in the microfluidic channel.
To overcome this problem, we fabricated three-dimensional (3D) electrodes at
the coplanar sensing region of an underlying microwave resonator. The 3D
electrodes are based on SU8 polymer which is then metallized by sputter
coating. With this system, we readily characterized a mixture composed of 12 um
and 20 um polystyrene particles and demonstrated separation without any
position-related calibration. The ratio of the electronic response of the two
particle types is approximately equal to the ratio of the particle volumes,
which indicates the generation of a uniform electric field at the sensing
region. The current work obviates the need for using multiple coplanar
electrodes and extensive processing of the data for the calibration of particle
height in a microfluidic channel: as such, it enables the fabrication of more
sophisticated microwave resonators for environmental and biological
applications
Inertial Imaging with Nanomechanical Systems
Mass sensing with nanoelectromechanical systems has advanced significantly during the last decade. With nanoelectromechanical systems sensors it is now possible to carry out ultrasensitive detection of gaseous analytes, to achieve atomic-scale mass resolution and to perform mass spectrometry on single proteins. Here, we demonstrate that the spatial distribution of mass within an individual analyte can be imaged—in real time and at the molecular scale—when it adsorbs onto a nanomechanical resonator. Each single-molecule adsorption event induces discrete, time-correlated perturbations to all modal frequencies of the device. We show that by continuously monitoring a multiplicity of vibrational modes, the spatial moments of mass distribution can be deduced for individual analytes, one-by-one, as they adsorb. We validate this method for inertial imaging, using both experimental measurements of multimode frequency shifts and numerical simulations, to analyse the inertial mass, position of adsorption and the size and shape of individual analytes. Unlike conventional imaging, the minimum analyte size detectable through nanomechanical inertial imaging is not limited by wavelength-dependent diffraction phenomena. Instead, frequency fluctuation processes determine the ultimate attainable resolution. Advanced nanoelectromechanical devices appear capable of resolving molecular-scale analytes
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
Intermodal coupling as a probe for detecting nanomechanical modes
Nanoelectromechanical systems provide ultrahigh performance in sensing applications. The sensing performance and functionality can be enhanced by utilizing more than one resonance mode of a nanoelectromechanical-systems device. However, it is often challenging to measure mechanical modes at high frequencies or modes that couple weakly to output transducers. In this paper, we propose the use of intermodal coupling as a mechanism to enable the detection of such modes. To implement this method, a probe mode is continuously driven and monitored using a phase-locked loop, while an auxiliary drive signal scans for other modes. Each time the auxiliary drive signal excites the corresponding mode by matching the mechanical frequency, the effective tension within the structure increases, which in turn causes a frequency shift in the probe mode. The location and width of these frequency shifts can be used to determine the frequency and quality factor of mechanical modes indirectly. Intermodal coupling can be used as a tool to obtain the spectrum of a mechanical structure even if some of these modes cannot be detected conventionally