298 research outputs found
Nanomechanical Thermal Response Modeling for Optimal Signal Estimation via Kalman filtering
No full textWe propose a thermal circuit model for nanomechanical infrared spectroscopy (NEMS-IR), suitable
for model-based filtering techniques such as Kalman filtering. This model accounts for the
resonator’s dual time constant response and its noise profiles, enabling optimal estimation of the
absorbed input power by the nanomechanical resonator. System identification utilizes a step response
(Figure 1a) and the power spectral density of the noise (Figure 1b). An adaptive Kalman filter, which
increases in bandwidth upon resonator illumination, is employed for precise input estimation (Figure
1c and 1d). Reproducibility and linearity are evaluated by conducting five measurements across three
power levels for both laser "on" and "off" transients (Figure 1e). Additionally, a staircase function is
applied to demonstrate the resonator's immunity to the slower second time constant when the
illuminating laser power is increased stepwise
Nanomechanical Photothermal Detectivity, Microscopy & Spectroscopy
No full textSuspended ceramic structures with nanometer-scale thickness, as well as 2D materials, serve as mechanically resonant structures with low mechanical energy loss, making them excellent candidates for thermal sensing applications. At TU Wien, our group explores photothermal IR detection, microscopy, and spectroscopy using nanomechanical resonators, commonly referred to as nanoelectromechanical systems (NEMS). These resonators are highly sensitive to temperature changes, which manifest as shifts or de-tuning of their resonant frequency. Consequently, any material placed on these resonators—whether a thin film for broadband IR absorption, dispersed molecules, or single molecules—can be detected if it absorbs light and dissipates heat. This means that the absorbing material, the analyte, becomes an integral part of the detection system itself, with no wavelength limitations, allowing for in situ measurements across the entire spectrum that the analyte can absorb. The choice of resonator material and its geometric design is crucial in minimizing noise and optimizing the resonator's response, which in turn enhances its noise equivalent power (NEP). We have successfully measured IR light in the range from 1 to 25 µm with an NEP of 7 pW/√Hz,[1] localized single dye molecules and determined the orientation of single nanorods,[2,3] measured and separated the IR spectra of nanograms of simultaneously desorbing species,[4] and opened new avenues for studying ultrafine particles, proteins, and catalysis.[5]
1. Piller, Markus, et al. "Thermal IR detection with nanoelectromechanical silicon nitride trampoline resonators." IEEE Sensors Journal 23.2 (2022): 1066-1071.
2. Chien, Miao-Hsuan, et al. "Single-molecule optical absorption imaging by nanomechanical photothermal sensing." Proceedings of the National Academy of Sciences 115.44 (2018): 11150-11155.
3. Kanellopulos, Kostas, Robert G. West, and Silvan Schmid. "Nanomechanical photothermal near infrared spectromicroscopy of individual nanorods." ACS photonics 10.10 (2023): 3730-3739.
4. Luhmann, Niklas, et al. "Nanoelectromechanical infrared spectroscopy with in situ separation by thermal desorption: Nems-ir-td." ACS sensors 8.4 (2023): 1462-1470.
5. West, Robert G., Kostas Kanellopulos, and Silvan Schmid. "Photothermal microscopy and spectroscopy with nanomechanical resonators." The Journal of Physical Chemistry C 127.45 (2023): 21915-21929
How bandwidth and sample points affect precision of Q-factor measurements in PiezoMEMS resonators
No full textPiezoelectric silicon MEMS resonators based on aluminum nitride (AlN) thin films are a versatile
technology platform for a multitude of sensor applications [1,2]. Given the moderate piezoelectric
coefficients of AlN and thus low stroke levels, such devices are commonly designed for resonant
operation [3]. Resonances in linear devices are characterized by two quantities, resonance frequency
! and quality factor . In this work, we examine the impact of bandwidth and number of samples
points within a given frequency range on the precision, by which can be measured
Psychometrische Eigenschaften einer deutschsprachigen Übersetzung des Mental Toughness Inventory (MTI-D)
No full textDas Mental Toughness Inventory (MTI; Middleton, Martin & Marsh, 2011) ist ein Selbstbeurteilungsinstrument zur Erfassung von 12 Facetten mentaler Stärke im Sport oder anderen leistungsbezogenen Kontexten. Ins Deutsche übersetzt, wurde das MTI–D an einer deutschsprachigen Stichprobe (N = 1 122), davon n = 914 Athletinnen und Athleten und n = 208 Studierende der Sportwissenschaft aus 41 Sportarten hinsichtlich Faktorstruktur, Messinvarianz, Reliabilität, Konstrukt- und Kriteriumsvalidität untersucht. Entsprechend der theoretischen Konzeption ergaben Bifaktorenanalysen für das MTI–D eine Struktur mit einem gemeinsamen Faktor und 12 spezifischen Faktoren. Die Reliabilität (ω) der Gesamtskala und der Subskalen lag zwischen .81 und .98, während die Werte für omega hierarchical subscale tiefer lagen (.07 ≤ ωHS ≤ .77). Der globale und die spezifischen Faktoren korrelierten hypothesenkonform mit dem Engagement und Leistungsniveau im Sport sowie dem Test of Performance Strategies (TOPS-D; Schmid, Birrer, Kaiser & Seiler, 2010) zur Erfassung mentaler Strategien im Sport. Zwar könnten einzelne Faktoren optimiert werden, doch es liegen Hinweise darauf vor, dass mit dem MTI–D mentale Stärke reliabel und valide erfasst werden kann
Modelling the Interaction of Non-Slender MEMS Resonators with Fluidic and Elastic Environments
No full textResonators with slender geometries are ubiquitous in microelectromechanical systems (MEMS).
They are key components in various applications like atomic force microscopy or mass sensing and
serve as building blocks for complex devices. However, the focus on slender resonator geometries
severely limits the freedom of design and the ability to tune the interaction between the resonator and
its environment. Going beyond slender structures is often not prohibited by fabrication limitations
but rather by difficulties in modelling. In this talk, we present methods for overcoming these
challenges and discuss how non-slender resonators interact with elastic and fluidic environments [1].
We show that the fluid-structure interaction changes significantly when transforming from a slender
beam to a wide plate resonator geometry [2]. By utilizing vibrational modes not present in slender
beam resonators, quality factors in fluids can be increased significantly compared to slender
resonators [3]. An elastic environment of a MEMS resonator is represented by the substrate to which
the resonator is anchored. The vibrational modes of non-slender MEMS resonators exhibit complex
elastic interactions with this anchoring region resulting in a strong dependence of anchor losses on
the vibrational mode. What is more, modal interactions change the anchor-loss-related quality factors
over orders of magnitude. Our results demonstrate that non-slender resonator geometries have several
advantages over conventional slender geometries and the methods presented here allow to tune the
interaction with different types of resonator environments
Transverse Vibration of Silicon Nanowires: Surface Properties
No full textExtreme miniaturization approaching single-digit nanometer linewidths is the outcome of the
continuous need for increased performance and sensitivity. Silicon Nanowires (Si NWs) are
promising building blocks with various applications in nanoelectromechanical systems. Despite
notable advancements in fabrication and integration technologies, thorough characterization of NWs
remains an ongoing process. Incorporating surface state with the native oxide and crystal anisotropy,
recently introduced ExtZP model combines analytical and molecular dynamics approaches thereby
providing a powerful, multiscale interpretation technique of quasistatic bending test results [1].
Simultaneously, transverse vibration is considered an ideal platform to study the surface effect on the
size-dependent mechanical properties of Si NWs. A monolithic fabrication method is employed to
fabricate Si NWs with nominal widths ranging from 10 nm to 80 nm. Their frequency response is
assessed using base excitation and a laser doppler vibrometer (LDV MSA-600, Polytec GmbH).
Surface properties (surface stresses and surface elastic constants) are then extracted through the
ExtZP model and compared with available models for a detailed inspection of the role played by
surface on transverse vibrational response of Si NWs
Faktorielle Validität einer deutschsprachigen Version des Mental Toughness Inventory (Middleton et al., 2005)
No full textReliabilität und Validität einer deutschsprachigen Übersetzung des Mental Toughness Inventory (MIT-D)
No full textInterview: Anne-Marie Fortier
No full textThis paper is an edited version of an email interview conducted by Debra Ferreday and Adi Kuntsman with Anne-Marie Fortier, the author of Multicultural Horizons: Diversity and the Limits of the Civil Nation (Routledge, 2008). Fortier’s work has been informative in the development of some of the arguments explored in this special issue; in their conversation Ferreday and Kuntsman asked her to comment on the ideas of haunting, racial imaginaries, nostalgia, national anxieties, political feelings and hopes for the future
Ferroelectric and energy storage characterization of PVDF-based thin films and nanocomposites
No full textFunctional materials, such as lead zirconate titanate (PZT) and barium titanate (BTO), are widely used in microelectromechanical systems (MEMS) due to their strong piezoelectric properties. However, the inherent stiffness of these ceramics limits their applicability where high mechanical flexibility is required. This limitation has led to the growing interest in piezoelectric polymers, particularly in ferroelectric poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoroethylene (P(VDF-TrFE)). These polymers offer a soft alternative to traditional piezoceramics, making them suitable for flexible MEMS applications. This thesis investigates the electromechanical behaviour of PVDF and P(VDF-TrFE) thin films within the context of polymer science. It specifically explores how processing parameters, surface microstructure, and crystalline phases influence the piezoelectric and ferroelectric properties of these materials. For this purpose, capacitor-type test structures were fabricated by depositing thin films of PVDF and P(VDF-TrFE) via spin-coating. Additionally, capacitors can be applied as energy storage devices, an area where ferroelectric polymers have gained significant interest due to their superior dielectric strength compared to conventional ceramics and higher dielectric permittivity than standard polymeric materials. To leverage these advantageous properties even further, this work focuses on developing P(VDF-TrFE)-based nanocomposites loaded with carboxymethyl cellulose nanofibers mixed with BTO polydopamine-based functionalized high-permittivity nanoparticles (CCNF-BTO@PDA). These nanocomposites were incorporated into spin-cast thin films of 2 μm thickness, which is ten times thinner than those typically reported. Despite challenges such as nanoparticle agglomeration, which became more pronounced in these thinner films and significantly affected the breakdown strength, these findings offer valuable insights for further research in spin-cast fluoropolymer-based nanocomposite thin films, especially when targeting the micrometre thickness range for MEMS applications
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