10 research outputs found
Controlling macropore formation in patterned n-type silicon: Existence of a pitch-dependent etching current density lower bound
No full textA novel power-controlling approach for integrated, conductometric gas sensors
No full textAn original power controlling driving/reading circuit for Porous Silicon JFET (PSJFET) gas sensors is presented. The PSJFET is an integrated p-channel JFET with two independent gates: a meso-structured PS layer, acting as a sensing, floating gate, which modulates the JFET current upon adsorption/desorption of specific analytes, and a high-impedance electric gate, which allows the JFET current tuning independently from analytes in the environment. The circuit exploits the independence of the sensing and electrical gate terminals to set/control the sensor power-dissipation, which is kept almost constant independently from adsorption/desorption-induced effects, while simultaneously carrying out a current-voltage conversion. For such a purpose, a negative feedback loop is used to modulate the PSJFET electric gate voltage, which becomes the output signal, while keeping constant the source-drain sensor current and, hence, the power dissipation. The proposed approach is validated by performing time-resolved measurements on PSJFET sensors under different NO2 concentrations (100ppb, 300ppb, 500ppb), at room temperature
Technology, characterization and preliminary sensing application of photoelectrosynthesized polypyrrole on microstructured silicon
No full textThe present work describes a novel technology for microstructuring polypyrrole based on the photoelectropolymerization of PPy films on micromachined n-type silicon (n-Si) substrates. The proposed approach conjugates the flexibility of micromachining techniques in fabricating three-dimensional (3D) microstructures with conducting polymers technology leading to the development of novel PPy films whose features at the microscale can be tailored to the specific applications. Photoelectropolymerization process has been previously studied on flat n-Si substrates and, under selected experimental conditions, on micromachined n-Si containing regular array of ordered macropores with pitch of 8 mu m, size (s) of 5 mu m and depth (d) of 10 mu m. Scanning Electron Microscopy (SEM) analysis of both flat and microstructured PPy films evidenced an isotropic polymers deposition uniformly covering the silicon substrates and perfectly replicating micromachined silicon features. The electrochemical response of photogenerated PPy films to selected probe has been observed and the role of micrometer-scale morphology in enhancing film recognition properties has been verified
Highly conformal growth of microstructured polypyrrole films by electrosynthesis on micromachined silicon substrates
No full textCapillary optofluidics by high-aspect-ratio photonic crystals
No full textIn this work, vertical, silicon/air one-dimensional photonic crystals (1DPhCs) are proposed as sensing elements for capillary optofluidics. As proof-of-concept, a drop-and-measure optofluidic platform that integrates a 1DPhC operating in the near-infrared region into a simple capillary microfluidic network is reported. The platform is fabricated by silicon electrochemical micromachining (ECM) technology and is optically characterized by measuring the shift of 1DPhC refelctivity upon capillary infiltration of liquids with different refractive indices into the PhC air-gaps. Experimental measures highlight that high reproducibility, good linearity, high sensitivity, and good limit of detection are achieved under capillary operation, thus foreseeing a novel generation of drop-and-measure platforms for refractometry/chemical analysis making use of PhCs
Coherent transport properties of a three-terminal hybrid superconducting interferometer
No full textWe present an exhaustive theoretical analysis of a double-loop Josephson proximity interferometer, such as the one recently realized by Strambini et al. for control of the Andreev spectrum via an external magnetic field. This system, called ω-SQUIPT, consists of a T-shaped diffusive normal metal (N) attached to three superconductors (S) forming a double-loop configuration. By using the quasiclassical Green-function formalism, we calculate the local normalized density of states, the Josephson currents through the device, and the dependence of the former on the length of the junction arms, the applied magnetic field, and the S/N interface transparencies. We show that by tuning the fluxes through the double loop, the system undergoes transitions from a gapped to a gapless state. We also evaluate the Josephson currents flowing in the different arms as a function of magnetic fluxes, and we explore the quasiparticle transport by considering a metallic probe tunnel-coupled to the Josephson junction and calculating its I-V characteristics. Finally, we study the performances of the ω-SQUIPT and its potential applications by investigating its electrical and magnetometric properties.QN/Nazarov Grou
Electrochemical Preparation of Micro and Nano Structures and Systems in Silicon for (Bio) Sensing and Nano (Medicine) Applications
No full textWhen dealing with biosensing and nanomedicine applications the length scale of targets may vary over more than 5 orders of magnitude moving from the molecular level (0.1-1 nm) up to the cell level (1-10 μm). A number of micro and nanostructuring technologies have been developed over the years to enable the preparation of both structures and systems with length scales suitable to match specific biological targets.
In this talk, electrochemical preparation of nano and micro structures and systems in silicon with length scales spanning over 5 order of magnitudes, able to target different applications both in (nano)medicine (e.g. sinusoid-like liver on a chip, nanopillars for cell transfection, 3D microincubators for tumor cell screening) and (bio)sensing (e.g. microneedles for transdermal biosensing, optical biosensors for point-of-care clinical diagnostics, chemitransitor sensors for environmental monitoring), is presented and discussed.
1. S.Mariani, V. Robbiano, L. M. Strambini, A. Debrassi, G. Egri, L. Dähne, G. Barillaro, Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing, Nature Communications, 9, 5256, 1-13 (2018)
2. B. Delalat, C. Cozzi, S. R. Ghaemi, G. Polito, F. E. Kriel, T. D. Michl, F. J. Harding, C. Priest, G. Barillaro, N. H. Voelcker, Microengineered Bioartificial Liver Chip for Drug Toxicity Screening, Advanced Functional Materials 1801825 (2018).
3. Robbiano, G. M. Paterno, A. A. La Mattina, S. G. Motti, G. Lanzani, F. Scotognella, G. Barillaro, Room-Temperature Low-Threshold Lasing From Monolithically Integrated Nanostructured Porous Silicon Hybrid Microcavities, ACS Nano12, 4536−4544 (2018).
4. J. Harding, S. Surdo, B. Delalat, C. Cozzi, R. Elnathan, S. Gronthos, N. H. Voelcker, G. Barillaro, Ordered Silicon Pillar Arrays Prepared by Electrochemical Micromachining: Substrates for High-Efficiency Cell Transfection, ACS Applied Materials and Interfaces, 8 (43), 29197-29202 (2016).
5. Mariani, L. M. Strambini, G. Barillaro, Femtomole Detection Of Proteins Using A Label-Free Nanostructured Porous Silicon Interferometer For Perspective Ultra-Sensitive Biosensing, ACS Analytical Chemistry, 88 (17), 8502-8509 (2016).
6. Mariani, L. Pino, L. M. Strambini, L. Tedeschi, G. Barillaro, 10000-Fold Improvement in Protein Detection Using Nanostructured Porous Silicon Interferometric Aptasensors, ACS Sensors, 1, 1471-1479(2016).
7. M. Sainato, L.M. Strambini, S. Rella, E. Mazzotta, G. Barillaro, Sub-Parts Per Million NO2 Chemi-Transistor Sensors Based on Composite Porous Silicon/Gold Nanostructures Prepared by Metal-Assisted Etching, ACS Applied Materials and Interfaces 7, 7136 (2015).
8. M. Strambini, A. Longo, S. Scarano, T. Prescimone, I. Palchetti, M. Minunni, D. Giannessi, G. Barillaro, Self-Powered Microneedle-Based Biosensors for Pain-Free High-Accuracy Measurement of Glycaemia in Interstitial Fluid, Biosensors and Bioelectronics,66, 162 (2015)
Extremophiles in an Antarctic Marine Ecosystem
No full textRecent attempts to explore marine microbial diversity and the global marine microbiome have indicated a large proportion of previously unknown diversity. However, sequencing alone does not tell the whole story, as it relies heavily upon information that is already contained within sequence databases. In addition, microorganisms have been shown to present small-to-large scale biogeographical patterns worldwide, potentially making regional combinations of selection pressures unique. Here, we focus on the extremophile community in the boundary region located between the Polar Front and the Southern Antarctic Circumpolar Current in the Southern Ocean, to explore the potential of metagenomic approaches as a tool for bioprospecting in the search for novel functional activity based on targeted sampling efforts. We assessed the microbial composition and diversity from a region north of the current limit for winter sea ice, north of the Southern Antarctic Circumpolar Front (SACCF) but south of the Polar Front. Although, most of the more frequently encountered sequences were derived from common marine microorganisms, within these dominant groups, we found a proportion of genes related to secondary metabolism of potential interest in bioprospecting. Extremophiles were rare by comparison but belonged to a range of genera. Hence, they represented interesting targets from which to identify rare or novel functions. Ultimately, future shifts in environmental conditions favoring more cosmopolitan groups could have an unpredictable effect on microbial diversity and function in the Southern Ocean, perhaps excluding the rarer extremophiles
