1,720,977 research outputs found
Micro-for-Nano: A Low-Power Platform for Nanomaterial Integration and Nanosensors Interface on 0.13μm CMOS Technology
No full textDuring the last years, material science has been focused on the exploration of the material characteristics at nanoscale. In fact, some materials show different properties only if they are designed with a nanometer structure. Even if they can be used to build macro devices (e.g., tactile surface, strain sensors), the nanostructured materials can reach high sensitivity or accuracy. Thin films [1], nanoparticles [2] and nanowires composites [3] have been widely used thanks to their sensitivity to mechanical strengths [4] or light stimuli [5-7]. In these cases, a large number of nanostructured elements have been merged in a single device to transduce macro-phenomena (e.g., strain, bending, pressure, temperature). Although nanomaterials can be used for standard sensor applications, the aim of nanotechnology is to exploit the dimension of the basic elements (e.g., nanoparticles) to conceive innovative applications at nanoscale. In order to exploit the ultra-small dimension of these materials, researchers addressed the development of nanodevices including only a single nanostructured element to increase sensitivity and accuracy. Nanomaterials, such as nanowires (NWs), bridging molecules or nanoparticles, are considered the basis for a new generation of bio-sensors able to interact with gases [8, 9], molecules (e.g., DNA molecules) or other bio-substances at nanoscale. Some examples are the lab-on-chip designed to implement drug detection using functionalized CNT [10] and the Electronic Nose able to identify different gas molecules [11]. The fabrication process of a nanosensor (or nanodevice) mainly consists in the integration of nanomaterials (previously synthesized for achieving the desired functionality) with metal electrodes. The fabrication process is actually complex and implies high costs. Different techniques can be used to connect nanomaterial with metal electrodes and, then, to the custom electronic interface. The most used methods for integration involve a stochastic deposition upon interdigitated electrodes [12] or chemical processes to directly grow the nanomaterials in-situ [13] or an electrically controlled deposition of nanomaterials dissolved in liquid solution [14]. The fabricated nanodevice is a passive component and it needs to be connected to a measurement system, involving long cables and therefore high parasitics. Fundamentally, when a nanomaterial is exposed to specific molecules or physical phenomena, its resistance or capacitance changes proportionally to the sensed quantity. Thus, the larger the variation of the resistance or capacitance of nanomaterials, the higher the sensitivity to specific phenomena. The electronic interface for passive nanosensors should be able to stimulate the nanomaterial and convert the large variation of its electrical characteristics to analog or digital signals compliant with commercial electronics. The nanomaterial signal is usually a current in the pA-μA range and the noise coupling, due to long interconnections, can easily affect the whole nanodevice sensitivity. Hence, a new approach for the nanosensor fabrication and for the read-out is strictly required to cut fabrication costs and improve measurement accuracy. The electronic interface needs to be placed as close as possible to avoid interferences at the interconnection cables. Anyway, the read-out system has also to overcome flicker-noise effects during DC or low-frequency measurements. In addition to the issues related to the measurement accuracy, a single nanosensor is not sufficient to produce reliable results because of the process variation in nanomaterial synthesis and nanodevice fabrication. Thus, an array of nanosensors is strongly suggested because a large number of nanodevices compensates the defects in single nanosensor fabrication. The measurement system provides the final results performing an average calculation of the nanosensor outputs. Actually, if the final aim is a complex system as the Electronic Nose [15] (i.e., an integrated multi-sensors system) or a bio-sensors for blood analysis [16], an array of nanosensors is strictly required given that different molecules have to be detected and average measurements are mandatory. This PhD thesis reports about a flexible platform implemented in CMOS technology for conceiving a Micro-for-Nano (M4N) system where nanosensors and microelectronics coexist on the same chip. The nanomaterial integration process (Chapter 2, Chapter 3), the read-out circuits for nanosensor interface (Chapter 4, Chapter 5) and the architecture to handle large number of integrated nanosensors (Chapter 6) will be described in the following chapters. The M4N project has been developed in collaboration with the Italian Institute of Tecnology (IIT@PoliTO), which has supported all the experiments needed to set-up the integration process and to characterize the designed CMOS circuit
When bio-Nanotechnology meets Microelectronics
No full textDuring the last years, material science was focusing on the exploration of the material characteristics at nanoscale. To completely exploit the ultra-small dimension and high sensitivity of these materials, researchers addressed the development of nanodevices including only a single nanostructured element, such as nanowires (NWs), nanotubes, molecules or nanoparticles. These nanomaterials can also be considered the basis for a new generation of bio-sensors able to interact with gas, molecules (e.g., DNA molecules) or other bio-substances at nanoscale. To electrically connect the nano-element, we use planar gold nanogaps (<10nm) organized in arrays and obtained through electromigration process controlled by a full custom PCB-based modular system. During first experiments, monolayers of conductive Thiophene molecules have been self-assembled onto the nanogap resulting in a gold-molecules-gold molecular junction. Even functionalized NWs can be placed in the nanogap using dielectrophoresis. The I/V characteristic of a Metal- Molecular-Metal junction shows that a plausible resistance is in the range 10MΩ – 10GΩ but it strongly depends on the size of NWs or on the type, the number and the length of bonded molecules on the nanogap. Basically, these new generation sensors rely on changes of electrical properties (R, C) of nanodevices that have to be converted into electrical signals with an ad-hoc interfacing circuit fabricated in a standard low-cost technology. The CMOS process satisfies these requirements. The design of the read-out circuit has to garantee: – large R and C read-out range, due to process variation of nanodevices; – high SNR, to measure ultra-low current flowing through molecular nanodevices; – low power consumption to support high densitity integration of nanosensors organized in array; A quasi-digital Resistance to time-domain converter (e.g., Resistance-to-Frequency(R2F), Resistance-to-Time(R2T), PWM) can be an adaptive and effective solution. The proposed R2F converter shows low measurement error (<1%) within the 50kΩ – 3GΩ range and consumes 142μW. Moreover, the last R2T prototype consumes only 8.5μW, it has higher linearity in the whole range with maximum measurement error of 0.8%
A Flexible Low-Power 130 nm CMOS Read-Out Circuit With Tunable Sensitivity for Commercial Robotic Resistive Pressure Sensors
No full textEnergy analysis methods and tools for modelling and Optimizing monitoring tyre systems
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Power-aware partitioning of data converters
No full textSerial data streaming, one of the most important functions in modern communication systems, is becoming more and more power consuming as bit-rate is increasing without standstill. In this work, we propose a novel technique for partitioning conventional N-bit registers in standard data converters, in order to reduce their switching activity, and therefore power consumption. The architecture here presented have a very low area overhead with respect to the standard ones for serializers and, furthermore, it allows different (i.e., custom) configurations for the partitioning. The proposed method even allows to extract idleness conditions of register banks in order to apply the well-known clock-gating technique to the circuit and thus furtherly reducing the total power consumption. This method has been applied to different data converters (i.e., serializers) in a base-band radio within an ultra low-power industrial design and the results highlight the effectiveness of the proposed techniqu
An Hardware-In-the-Design Methodology for Wireless Sensor Networks based on Event-Driven Impulse Radio Ultra-Wide Band
No full textThis paper conceptualizes and comments an Hardware-In-the-Loop-based methodology for the design and test of wireless links based on Impulse-Radio UWB. The paper analyses standard HDL simulation EDA tools for interfacing compatibility with the physical peripherals in a generic HIL configuration to define a general Hardware-In-the-Design methodology, i.e. the HIL validation in the first steps of a standard design flow. Our concept has been compared with AMS-HDL models and standard simulation flows and with real-time simulations on a flexible platform (e.g. FPGA). The design methodology is applied to a Wireless Sensor Network design based on event-driven IR-UWB (one-way node-to-node communication). Advantages of the introduced HIDF technique compared to standard design flows are presented and discusse
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