Theoretical study of quasi-longitudinal Lamb modes in SiN/c-AlN thin composite plates for liquid sensing applications

The propagation of quasi-longitudinal Lamb mode along SiN/c-AlN thin composite plates was modeled and analyzed aimed at the design of a sensor able to detect the parameters change of a liquid environment, such as added mass and viscosity changes. Three modes were identified that have high phase velocity and quite good electroacoustic coupling efficiency: the fundamental quasi symmetric mode (qS0) and two higher order quasi-longitudinal modes (qL1 and qL2) with a dominantly longitudinal displacement component at one plate side. The velocity and attenuation of these modes were calculated for different liquid viscosities, and the gravimetric and viscosity sensitivities of both the phase velocity and attenuation were theoretically calculated

An interdisciplinary approach to the nanomanipulation of SiO2 nanoparticles. Design, fabricationand feasibility

Although some recent developments in nanotechnology made the prospects of a direct mechanical manipulation of micro- or nano-objects quite realistic, there are still several concerns and difficulties that affect such an endeavor. This is probably due to the large base of knowledge that is necessary to approach the problem of handling a nano-object by means of a nano- or micro-device. Therefore, any progress in this field is possible only by means of an integrated and interdisciplinary approach, which takes into account different aspects of the phenomenon. During the actual pioneering phase, there is a certain convenience in handling nano-objects that: (a) have peculiar known characteristics; (b) are easily recognizable, and (c) are interesting to the scientific community. This paper presents the interdisciplinary activities that were necessary to set up an experiment where specifically synthesized SiO2 particles came in contact with the tips of specifically-designed and -fabricated nanomanipulators. SiO2 mesoporous nanoparticles (KCC-1), having a peculiar dendritic structure, have been selected as a suitable nano-object because of the possibility to easily modulate their morphology. The expected contact force has been also calculated by means of Finite Element Analysis (FEA) electro-mechanical simulations

In-lab characterization of HYPSOS, a novel stereo hyperspectral observing system: first results

HYPSOS (HYPerspectral Stereo Observing System, patented) is a novel remote sensing instrument able to extract the spectral information from the two channels of a pushbroom stereo camera; thus it simultaneously provides 4D information, spatial and spectral, of the observed features. HYPSOS has been designed to be a compact instrument, compatible with small satellite applications, to be suitable both for planetary exploration as well for terrestrial environmental monitoring. An instrument with such global capabilities, both in terms of scientific return and needed resources, is optimal for fully characterizing the observed surface of investigation. HYPSOS optical design couples a pair of folding mirrors to a modified three mirror anastigmat telescope for collecting the light beams from the optical paths of the two stereo channels; then, on the telescope focal plane, there is the entrance slit of an imaging spectrograph, which selects and disperses the light from the two stereo channels on a bidimensional detector. With this optical design, the two stereo channels share the large majority of the optical elements: this allowed to realize a very compact instrument, which needs much less resources than an equivalent system composed by a stereo camera and a spectrometer. To check HYPSOS actual performance, we realized an instrument prototype to be operated in a laboratory environment. The laboratory setup is representative of a possible flight configuration: the light diffused by a surface target is collimated on the HYPSOS channel entrance apertures, and the target is moved with respect to the instrument to reproduce the in- flight pushbroom acquisition mode. Here we describe HYPSOS and the ground support equipment used to characterize the instrument, and show the preliminary results of the instrument alignment activities

Compliant Nano-Pliers as a Biomedical Tool at the Nanoscale: Design, Simulation and Fabrication

This paper presents the development of a multi-hinge, multi-DoF (Degrees of Freedom) nanogripper actuated by means of rotary comb drives and equipped with CSFH (Conjugate Surface Flexure Hinges), with the goal of performing complex in-plane movements at the nanoscale. The design approach, the simulation and a specifically conceived single-mask fabrication process are described in detail and the achieved results are illustrated by SEM images. The first prototype presents a total overall area of (550 × 550) μm2, an active clamping area of (2 × 4) μm2, 600 nm-wide circular curved beams as flexible hinges for its motion and an aspect ratio of about 2.5. These features allow the proposed system to grasp objects a few hundred nanometers in size

Downsizing Effects on Micro and Nano Comb Drives

Downscaling has been a focal task of Electronics and Electromechanics in the last few decades, and a great engine for technological progress as well. Nevertheless, a scaling operation affects device physics, functioning and performance. The present paper investigates about the impact of scaling on a test case compliant electrostatic micro or nano actuator that is under development with two preferred micro fabrication methods, namely, thick SOI and thin amorphous silicon. A series of numerical trials on materials strength, electro-mechanical characteristics, sensitivity and overall actuation performance have been carried out at different grades of down-scaling and of aspect ratio. This gave rise to new design charts that we propose here as a predictive and friendly guide to select the most appropriate micro fabrication method

Assessing the consequences of prolonged usage of disposable face masks

Due to the SARS-CoV-2 outbreak, wearing a disposable face mask has become a worldwide daily routine, not only for medical operators or specialized personnel, but also for common people. Notwithstanding the undeniable positive effect in reducing the risk of virus transmission, it is important to understand if a prolonged usage of the same face mask can have effectiveness on filtering capability and potential health consequences. To this aim, we present three investigations. A survey, carried out in central Italy, offers an overview of the distorted public awareness of face mask usage. A functional study shows how prolonged wearing leads to substantial drops in humid air filtration efficiency. Finally, a morphological analysis reports the proliferation of fungal or bacteria colonies inside an improperly used mask. Our study highlights therefore that wearing a face mask is really beneficial only if it is used correctly.Funding Agencies|Italian Ministry of University and Research (MUR) through the Sapienza University Project 2021 "SMART FACE-MASK FOR MONITORING HEALT-RELATED PARAMETERS IN THE BREATHING ZONE" [RG12117A84C979D3]; Regione Lazio; Fondo Europeo di Sviluppo Regionale (FESR) [1398 001-36723]; Italian Ministry of Foreign Affairs and International Cooperation (MAECI) [PGR00843]</p

Terahertz current oscillations in a gated two-dimensional electron gas with antenna integrated at the channel ends

We studied terahertz current oscillations induced by a frequency-tunable radiation source in a AlGaAs/InGaAs/AlGaAs heterostructure field effect transistor channel. A planar antenna was integrated on-chip, and a substrate lens was used for broadband coupling of free-space radiation at 0.18-0.72 THz to the channel ends. Through spectral analysis of the detection signal, we identified two different mixing mechanisms: one related to channel current oscillations and the other to modulation of the gate-to-channel potential. Depending on gate bias and radiation frequency, the two mechanisms either compete or cooperate, leading to responsivity up to 300 V/W and noise equivalent power of 1 nW/Hz(0.5) (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4717464

Design of compressors for FEL pulses using deformable gratings

We present the optical layout of soft X-rays compressors using reflective grating specifically designed to give both positive or negative group-delay dispersion (GDD). They are tailored for chirped-pulse-amplification experiments with FEL sources. The optical design originates from an existing compressor with plane gratings already realized and tested at FERMI, that has been demonstrated capable to introduce tunable negative GDD. Here, we discuss two novel designs for compressors using deformable gratings capable to give both negative and positive GDD. Two novel designs are discussed: 1) a design with two deformable gratings and an intermediate focus between the twos, that is demonstrated capable to introduce positive GDD; 2) a design with one deformable grating giving an intermediate focus, followed by a concave mirror and a plane grating, that is capable to give both positive and negative GDD depending on the distance between the second mirror and the second grating. Both the designs are tunable in wavelength and GDD, by acting on the deformable gratings, that are rotated to tune the wavelength and the GDD and deformed to introduce the radius required to keep the spectral focus. The deformable gratings have a laminar profile and are ruled on a thin silicon plane substrate. A piezoelectric actuator is glued on the back of the substrate and is actuated to give a radius of curvature that is varying from infinite (plane) to few meters. The ruling procedure, the piezoelectric actuator and the efficiency measurements in the soft X-rays will be presented. Some test cases are discussed for wavelengths shorter than 12 nm

Terahertz plasmon cavity modes in a heterostructure transistor

We have observed plasmon cavity modes in a high-mobility two-dimensional electron gas by photocurrent spectroscopy in the 0.15-0.40 THz range. Spectral peaks due to standing wave nonlinearities are clearly observe