Proof Of Concept Measurements Research Articles

Simultaneous Scanning Ion Conductance and Electrochemical Microscopy in Lithium‐Ion Battery Research

AbstractDeeper understanding of processes involved in operation of lithium‐ion batteries (LIBs) is necessary to further optimize them for future applications. Extensive research was conducted on the formation of a solid electrolyte interphase (SEI) on negative battery electrodes, still leaving several questions unanswered. Scanning probe microscopies (SPMs) enable in situ and operando investigations and have the potential to explain some phenomena. Scanning electrochemical microscopy (SECM) and scanning ion conductance microscopy (SICM) could be employed in LIB studies. A novel SICM method based on the redox couple ferrocene/ferrocenium is introduced for applications in carbonate solvents widely used in LIBs. Proof of concept measurements were conducted with a micro milled copper circuit board as model substrate. Furthermore, the proposed SICM approach was hyphenated with feedback mode SECM resulting in the simultaneous mapping of morphology and electrochemical activity. A flexible dual‐probe arrangement was developed enabling usage of both SPM techniques at the same time, and furthermore, an easy replacement of both individual probes if needed. The setup was applied in the characterisation of commercial graphite electrodes for LIBs before and after conducting a pre‐charging protocol. Changes in electrochemical activity and topography of the graphite electrode were resolved in simultaneously generated SECM/SICM recordings.

Frequency Comb OFDM Radar System With High Range Resolution and Low Sampling Rate

Common orthogonal frequency-division multiplexing (OFDM)-based radar waveforms normally require high sampling rates if a good range resolution shall be achieved. In contrast, this article proposes a scheme that keeps the necessary sampling rates at the transmitter (Tx) and receiver (Rx) constant while simultaneously increasing the instantaneous signal bandwidth in the radar channel. In addition, not only a high range resolution but also a high unambiguous velocity can be achieved with the waveform. The scheme is based on the upconversion and downconversion of a thinned out OFDM signal with two different frequency combs at the Tx and Rx. In the downconversion process, the orthogonal subcarriers of the several subbands in the RF channel are interleaved in a way that they can be sampled by an analog-to-digital converter with a lower sampling rate than the overall signal bandwidth. The theoretical model of the waveform and the necessary signal processing steps are explained in detail and the proof of concept measurements are provided, which verifies the practical functionality of the proposed scheme.

Dual-angle open field wavefront sensor for simultaneous measurements of the central and peripheral human eye.

We have developed a novel dual-angle open field wavefront sensor. This device captures real-time foveal and peripheral Zernike aberrations, while providing natural binocular viewing conditions for the subjects. The simultaneous data recording enables accurate analysis of changes in ocular optics with accommodation overcoming any uncertainties caused by accommodative lag or lead. The instrument will be used in myopia research to study central and peripheral ocular optics during near work and to investigate the effects of optical myopia control interventions. Proof of concept measurements, performed on an artificial eye model and on 3 volunteers, showed good repeatability with foveal-peripheral data synchronization of 65 msec or better. The deviations from subjective cycloplegic refractions were not more than 0.31 D. Furthermore, we tested the dual-angle wavefront sensor in two novel measurement schemes: (1) focusing on a close target, and (2) accommodation step change.

Exploiting Direct Laser Writing for Hydrogel Integration into Fragile Microelectromechanical Systems.

The integration of chemo-responsive hydrogels into fragile microelectromechanical systems (MEMS) with reflective surfaces in the micron to submicron range is presented. Direct laser writing (DLW) for 3D microstructuring of chemoresponsive “smart” hydrogels on sensitive microstructures is demonstrated and discussed in detail, by production of thin hydrogel layers and discs with a controllable lateral size of 2 to 5 µm and a thickness of some hundred nm. Screening results of polymerizing laser settings for precision microstructuring were determined by controlling crosslinking and limiting active chain diffusion during polymerization with macromers. Macromers are linear polymers with a tunable amount of multifunctional crosslinker moieties, giving access to a broad range of different responsive hydrogels. To demonstrate integration into fragile MEMS, the gel was deposited by DLW onto a resonator with a 200 nm thick sensing plate with high precision. To demonstrate the applicability for sensors, proof of concept measurements were performed. The polymer composition was optimized to produce thin reproducible layers and the feasibility of 3D structures with the same approach is demonstrated.

Advanced application of a sublayer fence probe in highly instationary turbomachinery flows: observations on prestall instabilities

The present paper introduces a novel approach for measuring near wall flow velocities by utilizing a sublayer surface fence probe. Hereby, a difference in static pressure builds up over a microscopic obstacle within the viscous sublayer. An analytical model of the angular dependent pressure difference is employed to derive information about the flow direction. Furthermore, a computational preston tube approach has been used to calibrate the surface fence probe with regard to a flow velocity to be assigned to half of the fence height. Through the use of a sophisticated analyzing algorithm the flow direction and its velocity can be determined as a function of time. As a proof of concept measurements were conducted within the radial gap of an annular compressor rig yielding both mean and time resolved near wall flow fields. Former are in very good compliance with oil flow visualizations proving the methods accuracy. The experimental results give unprecedented insights into an unsteady flow phenomenon that arises when an axial compressor is operating close to its stalling limit. The presented technique allows for investigating turbomachinery areas which formerly were observable only by computational means.Graphical

Combined Layer/Particle Approaches in Surface Molecular Imprinting of Proteins: Signal Enhancement and Competition.

Herein we report novel approaches to the molecular imprinting of proteins utilizing templates sizing around 10 nm and some 100 nm. The first step comprised synthesizing nanoparticles of molecularly imprinted polymers (MIP) towards bovine serum albumin (BSA) and characterizing them according to size and binding capacity. In a second step, they were utilized as templates. Quartz crystal microbalances (QCM) coated with MIP thin films based on BSA MIP nanoparticles lead to a two-fold increase in sensor responses, compared with the case of directly using the protein as the template. This also established that individual BSA molecules exhibit different “epitopes” for molecular imprinting on their outer surfaces. In light of this knowledge, a possible MIP-based biomimetic assay format was tested by exposing QCM coated with BSA MIP thin films to mixtures of BSA and imprinted and non-imprinted polymer (NIP) nanoparticles. At high protein concentrations (1000 ppm) measurements revealed aggregation behavior, i.e., BSA binding MIP NP onto the MIP surface. This increased sensor responses by more than 30% during proof of concept measurements. At lower a BSA concentration (500 ppm), thin films and particles revealed competitive behavior.

ORGANIC SCINTILLATOR FOR REAL-TIME NEUTRON DOSIMETRY.

We developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV-0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cf neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.

A Novel Detection Method for Underwater Moving Targets by Measuring Their ELF Emissions with Inductive Sensors.

In this article, we propose a novel detection method for underwater moving targets by detecting their extremely low frequency (ELF) emissions with inductive sensors. The ELF field source of the targets is modeled by a horizontal electric dipole at distances more than several times of the targets’ length. The formulas for the fields produced in air are derived with a three-layer model (air, seawater and seafloor) and are evaluated with a complementary numerical integration technique. A proof of concept measurement is presented. The ELF emissions from a surface ship were detected by inductive electronic and magnetic sensors as the ship was leaving a harbor. ELF signals are of substantial strength and have typical characteristic of harmonic line spectrum, and the fundamental frequency has a direct relationship with the ship’s speed. Due to the high sensitivity and low noise level of our sensors, it is capable of resolving weak ELF signals at long distance. In our experiment, a detection distance of 1300 m from the surface ship above the sea surface was realized, which shows that this method would be an appealing complement to the usual acoustic detection and magnetic anomaly detection capability.

Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the nondestructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy system was tested at the Los Alamos Neutron Science Center’s weapons nuclear research facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics, such as the modulation transfer function and the detective quantum efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.

Serial weighting of micro-objects with resonant microchanneled cantilevers

Atomic force microscopy (AFM) cantilevers have proven to be very effective mass sensors. The attachment of a small mass to a vibrating cantilever produces a resonance frequency shift that can be monitored, providing the ability to measure mass changes down to a few molecules resolution. Nevertheless, the lack of a practical method to handle the catch and release process required for dynamic weighting of microobjects strongly hindered the application of the technology beyond proof of concept measurements. Here, a method is proposed in which FluidFM hollow cantilevers are exploited to overcome the standard limitations of AFM-based mass sensors, providing high throughput single object weighting with picogram accuracy. The extension of the dynamic models of AFM cantilevers to hollow cantilevers was discussed and the effectiveness of mass weighting in air was validated on test samples.

Volumetric HiLo microscopy employing an electrically tunable lens.

Electrically tunable lenses exhibit strong potential for fast motion-free axial scanning in a variety of microscopes. However, they also lead to a degradation of the achievable resolution because of aberrations and misalignment between illumination and detection optics that are induced by the scan itself. Additionally, the typically nonlinear relation between actuation voltage and axial displacement leads to over- or under-sampled frame acquisition in most microscopic techniques because of their static depth-of-field. To overcome these limitations, we present an Adaptive-Lens-High-and-Low-frequency (AL-HiLo) microscope that enables volumetric measurements employing an electrically tunable lens. By using speckle-patterned illumination, we ensure stability against aberrations of the electrically tunable lens. Its depth-of-field can be adjusted a-posteriori and hence enables to create flexible scans, which compensates for irregular axial measurement positions. The adaptive HiLo microscope provides an axial scanning range of 1 mm with an axial resolution of about 4 μm and sub-micron lateral resolution over the full scanning range. Proof of concept measurements at home-built specimens as well as zebrafish embryos with reporter gene-driven fluorescence in the thyroid gland are shown.

Extending nanoscale spectroscopy with titanium nitride probes

We present a means of controlling the stoichiometry of titanium nitride (TiN) coatings on probes for tip‐enhanced Raman spectroscopy measurements made using sputtering so that outstanding enhancements can be obtained. This provides a more robust alternative to gold‐coated tips that also has potential for tuning the plasmon resonance and working in new environments. Proof of concept measurements on poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonate) thin films demonstrate increases in the observed intensity with contrast values up to 3.1. TiN is mechanically, chemically, and thermally robust. When deposited under appropriate conditions it has optical properties, including a plasmon resonance, very similar to those of gold. However, the spontaneous formation of a surface TiNxOy layer with relatively high values of y has prevented attaining enhancements in tip‐enhanced Raman spectroscopy beyond that provided by the lightning rod effect. Depositing a thin layer of aluminum to form a passivating Al2O3 layer over the TiN plasmonic structure allows the stoichiometry achieved in the vacuum deposition to be maintained. Copyright © 2016 John Wiley & Sons, Ltd.

Attitude determination and control for centrifugal tether deployment on the ESTCube-1 nanosatellite

This paper presents the design, development, and pre-launch characterization of the ESTCube-1 Attitude Determination and Control System (ADCS). The design driver for the ADCS has been the mission requirement to spin up the satellite to 360 deg¢s i1 with controlled orientation of the spin axis and to acquire the angular velocity and the attitude during the scientific experiment. ESTCube-1 is a one-unit CubeSat launched on 7 May 2013, 2:06 UTC on board the Vega VV02 rocket. Its primary mission is to measure the Coulomb drag force exerted by a natural plasma stream on a charged tether and, therefore, to perform the basic proof of concept measurement and technology demonstration of electric solar wind sail technology. The attitude determination system uses three-axis magnetometers, three-axis gyroscopic sensors, and two-axis Sun sensors, a Sun sensor on each side of the satellite. While commercial off-the-shelf components are used for magnetometers and gyroscopic sensors, Sun sensors are custom- built based on analogue one-dimensional position sensitive detectors. The attitude of the satellite is estimated on board using an Unscented Kalman Filter. An ARM 32-bit processor is used for ADCS calculations. Three electromagnetic coils are used for attitude control. The system is characterized through tests and simulations. Results include mass and power budgets, estimated uncertainties as well as attitude determination and control performance. The system fulfils all mission requirements.

Determining the energy distribution of electrons produced in associative detachment: The electron spectrometer with multipole trap

Design of a novel instrument for the analysis of the kinetic energy of the detached electrons is presented. The electron spectrometer with multipole trap combines a radiofrequency ion trap with a magnetic adiabatic collimation filter and is capable of measuring the energy of electrons produced in the trap. The theory of operation and numerical simulations of the instrument are presented together with a proof of concept measurements using three different mechanisms of electron production – thermionic emission from a tungsten filament; laser photodetachment from O− anions; associative detachment of O− + H2, D2, and CO.

Development of a capillary electrophoresis–mass spectrometry method for small peptides in the soil solution

Small peptides are being investigated for their role in ecosystem cycling and plant uptake of organic N, but little is known of molecular forms in the soil solution. The aim of this study was to develop a capillary electrophoresis–tandem mass spectrometry procedure for profiling small peptides in the soil solution. Capillary electrophoresis–mass spectrometry was capable of separating and detecting a range of small peptide standards. Adequate recovery (>90%) of standard peptides spiked into samples of soil solution indicated that separation and detection were robust and not significantly affected by the sample matrix. The method was applied to samples of soil solution from grassland mesocosms filled with clay-loam soil from an abruptic lixisol. Soil solution (ultrafiltered <3 kDa) contained at least 298 putatively identified peptides with most being smaller than 600 Da. Less than 5% of small peptides contained basic amino acids, which may reflect their preferential adsorption to the soil stationary phase versus peptides comprised of acid or neutral amino acids. Capillary electrophoresis–mass spectrometry of small peptides is robust and has already yielded novel findings with its first proof of concept measurements on the soil solution.