36 research outputs found
In-situ growth optimization in focused electron-beam induced deposition
We present the application of an evolutionary genetic algorithm for the
in-situ optimization of nanostructures prepared by focused
electron-beam-induced deposition. It allows us to tune the properties of the
deposits towards highest conductivity by using the time gradient of the
measured in-situ rate of change of conductance as fitness parameter for the
algorithm. The effectiveness of the procedure is presented for the precursor
W(CO)6 as well as for post-treatment of Pt-C deposits obtained by dissociation
of MeCpPt(Me)3. For W(CO)6-based structures an increase of conductivity by one
order of magnitude can be achieved, whereas the effect for MeCpPt(Me)3 is
largely suppressed. The presented technique can be applied to all beam-induced
deposition processes and has great potential for further optimization or tuning
of parameters for nanostrucures prepared by FEBID or related techniques
A hybrid polymer/ceramic/semiconductor fabrication platform for high-sensitivity fluid-compatible MEMS devices with sealed integrated electronics
Active microelectromechanical systems can couple the nanomechanical domain
with the electronic domain by integrating electronic sensing and actuation
mechanisms into the micromechanical device. This enables very fast and
sensitive measurements of force, acceleration, or the presence of biological
analytes. In particular, strain sensors integrated onto MEMS cantilevers are
widely used to transduce an applied force to an electrically measurable signal
in applications like atomic force microscopy, mass sensing, or molecular
detection. However, the high Young's moduli of traditional cantilever materials
(silicon or silicon nitride) limit the thickness of the devices, and therefore
the deflection sensitivity that can be obtained for a specific spring constant.
Using softer materials such as polymers as the structural material of the MEMS
device would overcome this problem. However, these materials are incompatible
with high-temperature fabrication processes often required to fabricate high
quality electronic strain sensors. We introduce a pioneering solution that
seamlessly integrates the benefits of polymer MEMS technology with the
remarkable sensitivity of strain sensors, even under high-temperature
deposition conditions. Cantilevers made using this technology are inherently
fluid compatible and have shown up to 6 times lower force noise than their
conventional counterparts. We demonstrate the benefits and versatility of this
polymer/ceramic/semiconductor multi-layer fabrication approach with the
examples of self-sensing AFM cantilevers, and membrane surface stress sensors
for biomolecule detection
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Monitoring Dynamic Protein Expression in Single Living E. Coli. Bacterial Cells by Laser Tweezers Raman Spectroscopy
Laser tweezers Raman spectroscopy (LTRS) is a novel, nondestructive, and label-free method that can be used to quantitatively measure changes in cellular activity in single living cells. Here, we demonstrate its use to monitor changes in a population of E. coli cells that occur during overexpression of a protein, the extracellular domain of myelin oligodendrocyte glycoprotein (MOG(1-120)) Raman spectra were acquired of individual E. coli cells suspended in solution and trapped by a single tightly focused laser beam. Overexpression of MOG(1-120) in transformed E. coli Rosetta-Gami (DE3)pLysS cells was induced by addition of isopropyl thiogalactoside (IPTG). Changes in the peak intensities of the Raman spectra from a population of cells were monitored and analyzed over a total duration of three hours. Data was also collected for concentrated purified MOG(1-120) protein in solution, and the spectra compared with that obtained for the MOG(1-120) expressing cells. Raman spectra of individual, living E. coli cells exhibit signatures due to DNA and protein molecular vibrations. Characteristic Raman markers associated with protein vibrations, such as 1257 cm{sup -1}, 1340 cm{sup -1}, 1453 cm{sup -1} and 1660 cm{sup -1}, are shown to increase as a function of time following the addition of IPTG. Comparison of these spectra and the spectra of purified MOG protein indicates that the changes are predominantly due to the induction of MOG protein expression. Protein expression was found to occur mostly within the second hour, with a 470% increase relative to the protein expressed in the first hour. A 230% relative increase between the second and third hour indicates that protein expression begins to level off within the third hour. It is demonstrated that LTRS has sufficient sensitivity for real-time, nondestructive, and quantitative monitoring of biological processes, such as protein expression, in single living cells. Such capabilities, which are not currently available in flow cytometry, open up new possibilities for analyzing cellular processes occurring in single microbial and eukaryotic cells
Direct-write nanoscale printing of nanogranular tunnelling strain sensors for sub-micrometre cantilevers
The sensitivity and detection speed of cantilever-based mechanical sensors increases drastically through size reduction. The need for such increased performance for high-speed nanocharacterization and bio-sensing, drives their sub-micrometre miniaturization in a variety of research fields. However, existing detection methods of the cantilever motion do not scale down easily, prohibiting further increase in the sensitivity and detection speed. Here we report a nanomechanical sensor readout based on electron co-tunnelling through a nanogranular metal. The sensors can be deposited with lateral dimensions down to tens of nm, allowing the readout of nanoscale cantilevers without constraints on their size, geometry or material. By modifying the inter-granular tunnel-coupling strength, the sensors’ conductivity can be tuned by up to four orders of magnitude, to optimize their performance. We show that the nanoscale printed sensors are functional on 500 nm wide cantilevers and that their sensitivity is suited even for demanding applications such as atomic force microscopy
Quasielastic 12C(e,e'p) Reaction at High Momentum Transfer
We measured the 12C(e,e'p) cross section as a function of missing energy in
parallel kinematics for (q,w) = (970 MeV/c, 330 MeV) and (990 MeV/c, 475 MeV).
At w=475 MeV, at the maximum of the quasielastic peak, there is a large
continuum (E_m > 50 MeV) cross section extending out to the deepest missing
energy measured, amounting to almost 50% of the measured cross section. The
ratio of data to DWIA calculation is 0.4 for both the p- and s-shells. At w=330
MeV, well below the maximum of the quasielastic peak, the continuum cross
section is much smaller and the ratio of data to DWIA calculation is 0.85 for
the p-shell and 1.0 for the s-shell. We infer that one or more mechanisms that
increase with transform some of the single-nucleon-knockout into
multinucleon knockout, decreasing the valence knockout cross section and
increasing the continuum cross section.Comment: 14 pages, 7 figures, Revtex (multicol, prc and aps styles), to appear
in Phys Rev
Anticipated initial results from the NASA Mars 2020 Perseverance Rover Mastcam-Z multispectral, stereoscopic imaging investigation
Mastcam-Z is a high-heritage imaging system aboard NASA's Mars 2020 Perseverance rover that is based on the successful Mastcam investigation on the Mars Science Laboratory (MSL) Curiosity rover. It has all the capabilities of MSL Mastcam, and is augmented by a 4:1 zoom capability that will significantly enhance its stereo imaging performance for science, rover navigation, and in situ instrument and tool placement support. The Mastcam-Z camera heads are a matched pair of zoomable, focusable charge-coupled device (CCD) cameras that collect broad-band Red/green/blue (RGB) or narrow-band visible/near-infrared (VNIR; ~400-1000 nm) multispectral color data as well as direct solar images using neutral density filters. Each camera has a selectable field of view ranging from ~7.7° to ~31.9° diagonally, imaging at pixel scales from 67 to 283 µrad/pix (resolving features ~0.7 mm in size in the near field and ~3.3 cm in size at 100 m) from its position ~2 m above the surface on the Perseverance Remote Sensing Mast (RSM)
The Mars 2020 Perseverance Rover Mast Camera Zoom (Mastcam-Z) Multispectral, Stereoscopic Imaging Investigation
Mastcam-Z is a multispectral, stereoscopic imaging investigation on the Mars 2020 mission’s Perseverance rover. Mastcam-Z consists of a pair of focusable, 4:1 zoomable cameras that provide broadband red/green/blue and narrowband 400-1000 nm color imaging with fields of view from 25.6° × 19.2° (26 mm focal length at 283 μrad/pixel) to 6.2° × 4.6° (110 mm focal length at 67.4 μrad/pixel). The cameras can resolve (≥ 5 pixels) ∼0.7 mm features at 2 m and ∼3.3 cm features at 100 m distance. Mastcam-Z shares significant heritage with the Mastcam instruments on the Mars Science Laboratory Curiosity rover. Each Mastcam-Z camera consists of zoom, focus, and filter wheel mechanisms and a 1648 × 1214 pixel charge-coupled device detector and electronics. The two Mastcam-Z cameras are mounted with a 24.4 cm stereo baseline and 2.3° total toe-in on a camera plate ∼2 m above the surface on the rover’s Remote Sensing Mast, which provides azimuth and elevation actuation. A separate digital electronics assembly inside the rover provides power, data processing and storage, and the interface to the rover computer. Primary and secondary Mastcam-Z calibration targets mounted on the rover top deck enable tactical reflectance calibration. Mastcam-Z multispectral, stereo, and panoramic images will be used to provide detailed morphology, topography, and geologic context along the rover’s traverse; constrain mineralogic, photometric, and physical properties of surface materials; monitor and characterize atmospheric and astronomical phenomena; and document the rover’s sample extraction and caching locations. Mastcam-Z images will also provide key engineering information to support sample selection and other rover driving and tool/instrument operations decisions
Optical Trapping and Coherent Anti-Stokes Raman Scattering (CARS) Spectroscopy of Submicron-Sized Particles
Chan JW, Winhold H, LAne SM, Huser T. Optical Trapping and Coherent Anti-Stokes Raman Scattering (CARS) Spectroscopy of Submicron-Sized Particles. IEEE J.Select. Top.Quanum Electron. 2005;11(4):858-863