165 research outputs found
A continuous flow microelectrophoretic module for protein separation
No full textIn the framework of our research work, we are developing a microfluidic system that can be used as a pre-treatment device for the sample preparation in analytical microsystems, as biosensors, for instance. Sample pre-treatment phase is usually envisaged before chemical and biological analysis. For example, if we want to perform contaminants detection in a complex matrix as milk, we must consider that the sample consists in a solution of butterfat globules and water with dissolved carbohydrates and protein complexes. If we want a bio-sensor to perform a label free detection of some target-contaminants in milk, interferents in the matrix must be removed. Proteins are an important part of these interferents, and their concentration needs to be reduced, in order to avoid fouling and consequently the inhibition of the sensor, or false positive results in the analysis. We have designed and fabricated a SPLITT flow thin fractionation device for protein separation that is now under testing with a BSA solution
Coupling of electrons to intermolecular phonons in molecular charge transfer dimers: a resonance Raman study
No full textWe report resonance Raman scattering (RRS) spectra and Raman excitation profiles (REP) of a system containing π dimers of identical molecular radical ions measured with laser excitation in resonance with the charge transfer (CT) transition. A Peierls–Hubbard (PH) Hamiltonian has been used to model the investigated system and to calculate its optical and RRS properties. Results are reported for two polyoxometallate salts of tetrathiafulvalene (TTF), namely (TTF)2(W6O19) and (TTF)2(Mo6O19) whose structures contain almost isolated (TTF+)2 dimers. The RRS spectra of (TTF)2(W6O19), measured in resonance with the CT absorption band centered at 832 nm, show three phonon modes located at 55, 90, and 116 cm−1 which are strongly resonance enhanced. These modes have been associated to the out‐of‐phase combinations of the translational motions of the two molecules composing the dimer. Such modes are effective in modulating the intradimer transfer integral, thus providing an efficient mechanism for coupling with the electronic system and for enhancement of the scattering intensity at resonance with the CT transition. The REP for the three strongly coupled modes of (TTF)2(W6O19) have been measured with laser excitation wavelengths ranging from 740 to 930 nm. Quantitative analysis of the REP data has been performed based on a perturbative solution of the PH model to second order in the electron‐molecular‐vibration (EMV) and electron‐intermolecular‐phonon (EIP) interactions. The CT absorption profile and the REP’s have been calculated using a time correlator technique and the model parameters have been optimized in order to fit the experimental REP data. Infrared vibronic absorptions of (TTF)2(W6O19), originated by the EMV coupling, have been measured and independent information on the electronic parameters of the PH model have been derived. This has made the choice of the fitting parameters used for the REP calculations rather unambiguous and has allowed us to obtain, for the first time, reliable experimental estimates of the EIP coupling constants
Instability and Drift Phenomena in Switching RF-MEMS Microsystems
No full textMEMS switches include mobile beams in their mechanical structure and these suspended parts are essential for the device functioning. This paper illustrates the most important instability phenomena related to MEMS switches. Starting from the most important instability exploited in these devices—the electrical actuation—the paper also analyzes other important effects related to instability phenomena, which are very common in this type of technology. Instabilities due to dielectric charge trapping, fabrication tolerances, mechanical deformation, contact wear, and temperature variation are duly analyzed, giving a comprehensive view of the complexity encountered in the reliable functioning of these apparently simple devices
A Miniaturized SPLITT System for On-Line Protein Separation
No full textThe development of a microfluidic module for on-line protein separation is presented in this paper. The device is based on the SPLITT (Split flow Thin fractionation) technique and the separation of proteins is electrically driven by means of two platinum electrodes included in the structure of the microdevice. The microfluidic network is realized by means of a thin dry film structure, Ordyl SY 355, (thermo-compression lamination), laminated on three levels, which is patterned through a photolithographic technique. The device has been tested with a Bovine Serum Albumin (BSA) solution, through absorbance measurements with a spectrophotometer, with best achieved separation at the outlet of 40%, measured as relative concentration unbalance at output channels
Continuous binary protein separation in a microfabricated electrical split-flow thin fractionation (SPLITT) device
No full textDevelopment of a Passive Skin for Glass Building Surfaces in a Smart Electromagnetic Environment
No full textElectromagnetic metasurfaces (MTS), also referred to as Reconfigurable Intelligent Surfaces (RIS) in their dynamic form, have the potential to actively shape the wireless communication environment, particularly in 5G and 6G systems. They help overcome significant path loss issues, especially at millimeter-wave (mmWave) frequencies within the FR2 band. Our study focuses on MTS from a fabrication standpoint, highlighting the microfabrication methods employed to create a static and passive MTS prototype on a 6′′-optically transparent wafer substrate. This MTS design is intended for integration onto large glass surfaces commonly found in urban settings
Chromium in MEMS Technology
No full textThis chapter has the purpose to address several topics where chromium can be encountered in MEMS technology, and the different ways to exploit its unique properties in the fabrication of MEMS and more in general microsystem devices. The aim of this choice is also to collect in a clear and organized way many specific knowledge that can normally be found only scattered around in different and diverse sources of scientific and technological information. The structure of the chapter can be described as follows: first a short introductory section where it is explained what is MEMS technology, what are the general principles of MEMS microfabrication, and the types of devices that can be produced by this technology. Then a brief review of chromium chemical properties relevant for MEMS, also with reference of its compounds, including oxidation behavior and chemical etching properties is given. It follows a discussion on mechanical and physical properties of this metal, and a summary of common deposition techniques (PVD, sputtering, electroplating) for chromium and its compounds. A core section about different uses of chromium in MEMS technology is then presented: chromium for masks in photolithography, chromium as adhesion layer for structural and noble metals, chromium as structural material in thin film resistors and other less frequent uses. Finally a short section on chromium alloys and their exploitation in MEMS applications is reported
All porous silicon microcavities: growth and physics
No full textThe spontaneous emission of a material can be controlled by placing it in a micron-sized optical cavity. In this paper we introduce the subject and we discuss the realization, the physics and perspective applications of all porous silicon microcavities. The emission properties of the cavities have been characterized as a function of the temperature, of the excitation power and of the response time. Coupled microcavities are demonstrated. Modeling of the structure have been performed on the basis of a transfer matrix approximation
Chipless RFID Sensors for the Internet of Things: Challenges and Opportunities
No full textRadio-frequency identification (RFID) sensors are one of the fundamental components of the internet of things that aims at connecting every physical object to the cloud for the exchange of information. In this framework, chipless RFIDs are a breakthrough technology because they remove the cost associated with the chip, being at the same time printable, passive, low-power and suitable for harsh environments. After the important results achieved with multibit chipless tags, there is a clear motivation and interest to extend the chipless sensing functionality to physical, chemical, structural and environmental parameters. These potentialities triggered a strong interest in the scientific and industrial community towards this type of application. Temperature and humidity sensors, as well as localization, proximity, and structural health prototypes, have already been demonstrated, and many other sensing applications are foreseen soon. In this review, both the different architectural approaches available for this technology and the requirements related to the materials employed for sensing are summarized. Then, the state-of-the-art of categories of sensors and their applications are reported and discussed. Finally, an analysis of the current limitations and possible solution strategies for this technology are given, together with an overview of expected future developments
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