A 32-by-32 CMOS microelectrode array for capacitive biosensing and impedance spectroscopy

This paper presents the design of a 1024-channel dual-modality CMOS biosensor suitable for both capacitive sensing and impedance spectroscopy. The chip serves as a platform for detection, localization and monitoring of bacteria and can be adopted for affinity-based assays. The chip features a 32×32 array of unpassivated metal electrodes formed on the top metal of a 0.18μm CMOS process, with an overall sensing area of 2.06 mm2. The system design is based on a shared in-pixel integrator that can be used as a charge amplifier for capacitive sensing (CS) or as part of a transimpedance amplifier for electrical impedance spectroscopy (EIS). The CS mode is capable of a operation bandwidth of 50 MHz at a current consumption of 82 μA per pixel. The EIS channel operates over a bandwidth between 100 Hz and 1 MHz with a total input-referred current noise of 48 pArms and a current consumption of 210 μA per channel

Wideband Fully-Programmable Dual-Mode CMOS Analogue Front-End for Electrical Impedance Spectroscopy

This paper presents a multi-channel dual-mode CMOS analogue front-end (AFE) for electrochemical and bioimpedance analysis. Current-mode and voltage-mode readouts, integrated on the same chip, can provide an adaptable platform to correlate single-cell biosensor studies with large-scale tissue or organ analysis for real-time cancer detection, imaging and characterization. The chip, implemented in a 180-nm CMOS technology, combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar electrical impedance spectroscopy (EIS) analysis. Each VR channel occupies an area of 0.48 mm 2 , is capable of an operational bandwidth of 8 MHz and a linear gain in the range between -6 dB and 42 dB. The gain of the CR channel can be set to 10 kΩ, 50 kΩ or 100 kΩ and is capable of 80-dB dynamic range, with a very linear response for input currents between 10 nA and 100 μ A. Each CR channel occupies an area of 0.21 mm 2 . The chip consumes between 530 μ A and 690 μ A per channel and operates from a 1.8-V supply. The chip was used to measure the impedance of capacitive interdigitated electrodes in saline solution. Measurements show close matching with results obtained using a commercial impedance analyser. The chip will be part of a fully flexible and configurable fully-integrated dual-mode EIS system for impedance sensors and bioimpedance analysis

Dual-mode CMOS analog front-end (AFE) for electrical impedance spectroscopy (EIS) systems

This paper presents the operation of a dualmode wideband CMOS analog front-end (AFE) for electrical impedance spectroscopy. The chip combines two current-readout (CR) channels and four voltage-readout (VR) channels suitable for both bipolar and tetrapolar EIS analysis. The chip addresses the need for flexible readout units for real-time simultaneous single-cell and large scale tissue/organ analysis. Postlayout simulations show that the VR channel is capable of wideband operation up to 12 MHz with noise floor as low as 16.4 nV/Hz1/2. A 2-bit control allows to select between a high-frequency low-gain channel and a bandwidth-limited high-gain channel. Each VR channel occupies an area of 0.48 mm2. The CR channel is capable of 80 dB of dynamic range, by converting currents between 1 nA to 10μA, while achieving a noise floor of 1.4 pA/Hz1/2. An automatic gain control (AGC) unit can be enabled in order maintain the sensor signal within the ADC dynamic range. Each CR channel occupies an area of 0.21 mm2. The chip consumes between 290 μA and 690 μA per channel and operates from a 1.8 V supply. The chip will be part of a fully flexible and configurable dual-mode EIS systems for impedance sensors and bioimpedance analysis

Mechanical behaviour with temperatures of aluminum matrix composites with CNTs

Aluminum is a very useful structural metal employed in different industrial sectors, in particular it is used in large quantities in automotive, aeronautic and nautical industries. The main reasons of its wide use are: a very good oxidation resistance, excellent ductility, low melting temperature (660 °C) and low density (2.71 g/cm3). However, in order to reduce the emissions and fuel consumption is necessary to reduce the overall weight of vehicles by increasing mechanical properties of the structural material. The improvement of mechanical properties is normally achieved through use of reinforcement in materials, used like matrix, in order to improve some specific characteristics. In this work composites of carbon nanotubes (CNTs) dispersed in aluminum were made. The most difficulties in the preparation of this type of composite are represented by the low wettability between metallic matrix and fillers and the possibility of the oxidation of metal during melting with consequent decreasing of mechanical proprieties. The composite was obtained by three consecutive step: the first one is the functionalization of fillers surface to improve the fillers dispersion, the second one is the dispersion of fillers in the matrix by powder mixing and the third one is the melting and casting of the mix prepared. In particular, fillers used are multi walled carbon nanotubes (MWCNTs) with functionalized surface by treatment with a solfonitric solution. Melting and casting are carried out with the aid of an induction furnace with a controlled atmosphere system and centrifugal casting. Argon is the inert gas used to prevent the oxidation of aluminium during fusion. Young’s modulus was evaluated at different temperature and correlated with the different CNTs percentage. The dispersion rate of fillers and the microstructure of the sample were evaluated by FESEM micrograph

Firm exit during economic slowdowns: does foreign ownership matter?

Do multinationals’ activities contribute to the severity of global economic crisis by quickly closing down facilities or otherwise allow to mitigating some of the worst effects, by remaining rooted in the local economy and thus reducing lay-offs and output contraction in the host countries? The present paper provides an empirical analysis on the link between foreign ownership and firm survival over an almost 20-year period and during two economic downturns in particular, using an extensive firm-level database and applying hazard models. We analyse the determinants of exit of firms and investigate whether there are significant differences in the hazard rates of foreign and domestic firms when controlling for firm and industry specificities. Additionally we assess whether the foreignness effect alters during economic downturns and whether any spillovers arise from the multinationals’ presence in the industry. After controlling for several firm and industry specific characteristics, we find that foreign firms exhibit higher failure rates over the time period as a whole. However, during economic slowdowns domestic and foreign firms do not exhibit different chances of survival and exit. Finally, regarding potential spillovers, our results suggest that foreign presence may impact positively upon local firms’ survival

Optimal irreversible stimulated emission

We studied the dynamics of an initially inverted atom in a semi-infinite waveguide, in the presence of a single propagating photon. We show that atomic relaxation is enhanced by a factor of 2, leading to maximal bunching in the output field. This optimal irreversible stimulated emission is a novel phenomenon that can be observed with state-of-the-art solid-state atoms and waveguides. When the atom interacts with two one-dimensional electromagnetic environments, the preferential emission in the stimulated field can be exploited to efficiently amplify a classical or a quantum state.Comment: 9 pages, 6 figure

Generation of 11-fs dark pulses via coherent perfect absorption in plasmonic metamaterial

Dark pulses are dips in power of electro magnetic radiation on a constant background that are often accompanied by a phase jump across the intensity minimum. Since their discovery, dark pulses have attracted considerable attention in many fields such as dark solitons and optical communications. Here we report generation of 11 fs dark pulses using the regime of “perfect absorption”. When two coherent counter-propagating electromagnetic waves of the same intensity form a standing wave, a thin absorber placed in the antinode of the wave could completely dissipate energy of both waves if its traveling wave absorption is 50%. If one of the waves is a “gate pulse” in time domain, the “perfect absorption” regime will exist only during the pulse, when a dip in power of “carrier pulse” will be created. “Dark pulses” are generated by positioning plasmonic absorber in the anti-node of the standing wave and balancing peak intensities . These dark pulses are characterized using cross-correlation technique. Measured width of the “dark pulse” is border than 6 fs “gate pulse”, which is nearly 11fs as shown in Fig. 1B. Width of the “dark pulse” is limited by transient plasmonic absorption establishes with completion of the plasmon relaxation time, which is typically 11fs in gold nanostructures. We argue that bandwidth of dark pulses is limited by the plasmon relaxation time of the absorber

A high power CMOS class-D amplifier for inductive-link medical transmitters

Powering of medical implants by inductive coupling is an effective technique, which avoids the use of bulky implanted batteries or transcutaneous wires. On the external unit side, class-D and class-E power amplifiers (PAs) are conventionally used thanks to their high efficiency at high frequencies. The initial specifications driving this work require the use of multiple independent stimulators, which imposes serious constraints on the area and functionality of the external unit. An integrated circuit class-D PA has been designed to provide both small area and enhanced functionality, the latter achieved by the addition of an on-chip phased-locked loop (PLL), a dead-time generator and a phase detector. The PA has been designed in a 0.18μm CMOS high-voltage process technology and occupies an area of 9.86 mm2. It works at frequencies up to 14 MHz and 30 V supply and efficiencies higher than 80% are obtained at 14 MHz. The PA is intended for a closed-loop transmitter system that optimises power delivery to medical implants