Lab-on-PCB Devices

Lab-on-PCB devices can be considered an emerging technology. In fact, most of the contributions have been published during the last 5 years. It is mainly focussed on both biomedical and electronic applications. The book includes an interesting guide for using the different layers of the Printed Circuit Boards for developing new devices; guidelines for fabricating PCB-based electrochemical biosensors, and an overview of fluid manipulation devices fabricated using Printed Circuit Boards. In addition, current PCB-based devices are reported, and studies for several aspects of research and development of lab-on-PCB devices are described

Microstimulation and multicellular analysis: A neural interfacing system for spatiotemporal stimulation

Willfully controlling the focus of an extracellular stimulus remains a significant challenge in the development of neural prosthetics and therapeutic devices. In part, this challenge is due to the vast set of complex interactions between the electric fields induced by the microelectrodes and the complex morphologies and dynamics of the neural tissue. Overcoming such issues to produce methodologies for targeted neural stimulation requires a system that is capable of (1) delivering precise, localized stimuli a function of the stimulating electrodes and (2) recording the locations and magnitudes of the resulting evoked responses a function of the cell geometry and membrane dynamics. In order to improve stimulus delivery, we developed microfabrication technologies that could specify the electrode geometry and electrical properties. Specifically, we developed a closed-loop electroplating strategy to monitor and control the morphology of surface coatings during deposition, and we implemented pulse-plating techniques as a means to produce robust, resilient microelectrodes that could withstand rigorous handling and harsh environments. In order to evaluate the responses evoked by these stimulating electrodes, we developed microscopy techniques and signal processing algorithms that could automatically identify and evaluate the electrical response of each individual neuron. Finally, by applying this simultaneous stimulation and optical recording system to the study of dissociated cortical cultures in multielectode arrays, we could evaluate the efficacy of excitatory and inhibitory waveforms. Although we found that the proximity of the electrode is a poor predictor of individual neural excitation thresholds, we have shown that it is possible to use inhibitory waveforms to globally reduce excitability in the vicinity of the electrode. Thus, the developed system was able to provide very high resolution insight into the complex set of interactions between the stimulating electrodes and populations of individual neurons.Ph.D.Committee Chair: Stephen P. DeWeerth; Committee Member: Bruce Wheeler; Committee Member: Michelle LaPlaca; Committee Member: Robert Lee; Committee Member: Steve Potte

Development of a silicon photomultiplier based innovative and low cost positron emission tomography scanner.

The Silicon Photomultiplier (SiPM) is a state-of-the-art semiconductor photodetector consisting of a high density matrix (up to 104) of independent pixels of micro-metric dimension (from 10 μm to 100 μm) which form a macroscopic unit of 1 to 6 mm2 area. Each pixel is a single-photon avalanche diode operated with a bias voltage of a few volts above the breakdown voltage. When a charge carrier is generated in a pixel by an incoming photon or a thermal effect, a Geiger discharge confined to that pixel is initiated and an intrinsic gain of about 106 is obtained. The output signal of a pixel is the same regardless of the number of interacting photons and provide only a binary information. Since the pixels are arranged on a common Silicon substrate and are connected in parallel to the same readout line, the SiPM combined output response corresponds to the sum of all fired pixel currents. As a result, the SiPM as a whole is an analogue detector, which can measure the incoming light intensity. Nowadays a great number of companies are investing increasing efforts in SiPM detector performances and high quality mass production. SiPMs are in rapid evolution and benefit from the tremendous development of the Silicon technology in terms of cost production, design flexibility and performances. They have reached a high single photon detection sensitivity and photon detection efficiency, an excellent time resolution, an extended dynamic range. They require a low bias voltage and have a low power consumption, they are very compact, robust, flexible and cheap. Considering also their intrinsic insensitivity to magnetic field they result to have an extremely high potential in fundamental and applied science (particle and nuclear physics, astrophysics, biology, environmental science and nuclear medicine) and industry. The SiPM performances are influenced by some effects, as saturation, afterpulsing and crosstalk, which lead to an inherent non-proportional response with respect to the number of incident photons. Consequently, it is not trivial to relate the measured electronic signal to the corresponding light intensity. Since for most applications it is desirable to qualify the SiPM response (i.e in order to properly design a detector for a given application, perform corrections on measurements or on energy spectra, calibrate a SiPM for low light measurements, predict detector performance) the implementation of characterization procedures plays a key role. The SiPM field of application that has been considered in this thesis is the Positron Emission Tomography (PET). PET represents the most advanced in-vivo nuclear imaging modality: it provides functional information of the physiological and molecular processes of organs and tissues. Thanks to its diagnostic power, PET has a recognized superiority over all other imaging modalities in oncology, neurology and cardiology. SiPMs are usually successfully employed for the PET scanners because they allow the measurement of the Time Of Flight of the two coincidence photons to improve the signal to noise ratio of the reconstructed images. They also permit to perfectly combine the functional information with the anatomical one by inserting the PET scanner inside the Magnetic Resonance Imaging device. Recently, PET technology has also been applied to preclinical imaging to allow non invasive studies on small animals. The increasing demand for preclinical PET scanner is driven by the fact that small animals host a large number of human diseases. In-vivo imaging has the advantage to enable the measurement of the radiopharmaceutical distribution in the same animal for an extended period of time. As a result, PET represents a powerful research tool as it offers the possibility to study the abnormalities at the origin of a disease, understand its dynamics, evaluate the therapeutic response and develop new drugs and treatments. However, the cost and the complexity of the preclinical scanners are limiting factors for the spread of PET technology: 70-80% of small-animal PET is concentrated in academic or government research laboratories. The EasyPET concept proposed in this Thesis, protected under a patent filed by Aveiro University, aims to achieve a simple and affordable preclinical PET scanner. The innovative concept is based on a single pair of detector kept collinear during the whole data acquisition and a moving mechanism with two degrees of freedom to reproduce the functionalities of an entire PET ring. The main advantages are in terms of the reduction of the complexity and cost of the PET system. In addition the concept is bound to be robust against acollinear photoemission, scatter radiation and parallax error. The sensitivity is expected to represent a fragility due to the reduced geometrical acceptance. This drawback can be partially recovered by the possibility to accept Compton scattering events without introducing image degradation effects, thanks to the sensor alignment. A 2D imaging demonstrator has been realized in order to assess the EasyPET concept and its performance has been analyzed in this Thesis to verify the net balance between competing advantages and drawbacks. The demonstrator had a leading role in the outreach activity to promote the EasyPET concept and a significant outcome is represented by the new partners that recently joined the collaboration. The EasyPET has been licensed to Caen S.p.a. and, thanks to the participation of Nuclear Instruments to the electronic board re-designed, a new prototype has been realized with additional improvements concerning the mechanics and the control software. In this Thesis the prototype functionalities and performances are reported as a result of a commissioning procedure. The EasyPET will be commercialized by Caen S.p.a. as a product for the educational market and it will be addressed to high level didactic laboratories to show the operating principles and technology behind the PET imaging. The topics mentioned above will be examined in depth in the following Chapters according to the subsequent order. In Chapter 1 the Silicon Photomultiplier will be described in detail, from their operating principle to their main application fields passing through the advantages and the drawback effects connected with this type of sensor. Chapter 2 is dedicated to a SiPM standard characterization method based on the staircase and resolving power measurement. A more refined analysis involves the Multi-Photon spectrum, obtained by integrating the SiPM response to a light pulse. It exploits the SiPM single photon sensitivity and its photon number resolving capability to measure some of its properties of general interest for a multitude of potential applications, disentangling the features related to the statistics of the incident light. Chapter 3 reports another SiPM characterization method which implements a post-processing of the digitized SiPM waveforms with the aim of extracting a full picture of the sensor characteristics from a unique data-set. The procedure is very robust, effective and semi-automatic and suitable for sensors of various dimensions and produced by different vendors. Chapter 4 introduces the Positron Emission Tomography imaging: its principle, applications, related issues and state of the art of PET scanner will be explained. Chapter 5 deals with the preclinical PET, reporting the benefits and the technological challenges involved, the performance of the commercially available small animal PET scanners, the main applications and the frontier research in this field. In Chapter 6 the EasyPET concept is introduced. In particular, the basic idea behind the operating principle, the design layout and the image reconstruction will be illustrated and then assessed through the description and the performance analysis of the EasyPET proof of concept and demonstrator. The effect of the use of different sensor to improve the light collection and the coincidence detection efficiency, together with the analysis of the importance of the sensor and the crystal alignment will be reported in Chapter 7. The design, the functionalities and the commissioning of the EasyPET prototype addressed to the educational market will be defined in Chapter 8. Finally, Chapter 9 contains a summary of the conclusions and an outlook of the future research studies

Biomedical Engineering

Biomedical engineering is currently relatively wide scientific area which has been constantly bringing innovations with an objective to support and improve all areas of medicine such as therapy, diagnostics and rehabilitation. It holds a strong position also in natural and biological sciences. In the terms of application, biomedical engineering is present at almost all technical universities where some of them are targeted for the research and development in this area. The presented book brings chosen outputs and results of research and development tasks, often supported by important world or European framework programs or grant agencies. The knowledge and findings from the area of biomaterials, bioelectronics, bioinformatics, biomedical devices and tools or computer support in the processes of diagnostics and therapy are defined in a way that they bring both basic information to a reader and also specific outputs with a possible further use in research and development

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Miniature high dynamic range time-resolved CMOS SPAD image sensors

Since their integration in complementary metal oxide (CMOS) semiconductor technology in 2003, single photon avalanche diodes (SPADs) have inspired a new era of low cost high integration quantum-level image sensors. Their unique feature of discerning single photon detections, their ability to retain temporal information on every collected photon and their amenability to high speed image sensor architectures makes them prime candidates for low light and time-resolved applications. From the biomedical field of fluorescence lifetime imaging microscopy (FLIM) to extreme physical phenomena such as quantum entanglement, all the way to time of flight (ToF) consumer applications such as gesture recognition and more recently automotive light detection and ranging (LIDAR), huge steps in detector and sensor architectures have been made to address the design challenges of pixel sensitivity and functionality trade-off, scalability and handling of large data rates. The goal of this research is to explore the hypothesis that given the state of the art CMOS nodes and fabrication technologies, it is possible to design miniature SPAD image sensors for time-resolved applications with a small pixel pitch while maintaining both sensitivity and built -in functionality. Three key approaches are pursued to that purpose: leveraging the innate area reduction of logic gates and finer design rules of advanced CMOS nodes to balance the pixel’s fill factor and processing capability, smarter pixel designs with configurable functionality and novel system architectures that lift the processing burden off the pixel array and mediate data flow. Two pathfinder SPAD image sensors were designed and fabricated: a 96 × 40 planar front side illuminated (FSI) sensor with 66% fill factor at 8.25μm pixel pitch in an industrialised 40nm process and a 128 × 120 3D-stacked backside illuminated (BSI) sensor with 45% fill factor at 7.83μm pixel pitch. Both designs rely on a digital, configurable, 12-bit ripple counter pixel allowing for time-gated shot noise limited photon counting. The FSI sensor was operated as a quanta image sensor (QIS) achieving an extended dynamic range in excess of 100dB, utilising triple exposure windows and in-pixel data compression which reduces data rates by a factor of 3.75×. The stacked sensor is the first demonstration of a wafer scale SPAD imaging array with a 1-to-1 hybrid bond connection. Characterisation results of the detector and sensor performance are presented. Two other time-resolved 3D-stacked BSI SPAD image sensor architectures are proposed. The first is a fully integrated 5-wire interface system on chip (SoC), with built-in power management and off-focal plane data processing and storage for high dynamic range as well as autonomous video rate operation. Preliminary images and bring-up results of the fabricated 2mm² sensor are shown. The second is a highly configurable design capable of simultaneous multi-bit oversampled imaging and programmable region of interest (ROI) time correlated single photon counting (TCSPC) with on-chip histogram generation. The 6.48μm pitch array has been submitted for fabrication. In-depth design details of both architectures are discussed

Ultra-thin and flexible CMOS technology: ISFET-based microsystem for biomedical applications

A new paradigm of silicon technology is the ultra-thin chip (UTC) technology and the emerging applications. Very thin integrated circuits (ICs) with through-silicon vias (TSVs) will allow the stacking and interconnection of multiple dies in a compact format allowing a migration towards three-dimensional ICs (3D-ICs). Also, extremely thin and therefore mechanically bendable silicon chips in conjunction with the emerging thin-film and organic semiconductor technologies will enhance the performance and functionality of large-area flexible electronic systems. However, UTC technology requires special attention related to the circuit design, fabrication, dicing and handling of ultra-thin chips as they have different physical properties compared to their bulky counterparts. Also, transistors and other active devices on UTCs experiencing variable bending stresses will suffer from the piezoresistive effect of silicon substrate which results in a shift of their operating point and therefore, an additional aspect should be considered during circuit design. This thesis tries to address some of these challenges related to UTC technology by focusing initially on modelling of transistors on mechanically bendable Si-UTCs. The developed behavioural models are a combination of mathematical equations and extracted parameters from BSIM4 and BSIM6 modified by a set of equations describing the bending-induced stresses on silicon. The transistor models are written in Verilog-A and compiled in Cadence Virtuoso environment where they were simulated at different bending conditions. To complement this, the verification of these models through experimental results is also presented. Two chips were designed using a 180 nm CMOS technology. The first chip includes nMOS and pMOS transistors with fixed channel width and two different channel lengths and two different channel orientations (0° and 90°) with respect to the wafer crystal orientation. The second chip includes inverter logic gates with different transistor sizes and orientations, as in the previous chip. Both chips were thinned down to ∼20m using dicing-before-grinding (DBG) prior to electrical characterisation at different bending conditions. Furthermore, this thesis presents the first reported fully integrated CMOS-based ISFET microsystem on UTC technology. The design of the integrated CMOS-based ISFET chip with 512 integrated on-chip ISFET sensors along with their read-out and digitisation scheme is presented. The integrated circuits (ICs) are thinned down to ∼30m and the bulky, as well as thinned ICs, are electrically and electrochemically characterised. Also, the thesis presents the first reported mechanically bendable CMOS-based ISFET device demonstrating that mechanical deformation of the die can result in drift compensation through the exploitation of the piezoresistive nature of silicon. Finally, this thesis presents the studies towards the development of on-chip reference electrodes and biodegradable and ultra-thin biosensors for the detection of neurotransmitters such as dopamine and serotonin

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Topical Workshop on Electronics for Particle Physics

The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities

The 1991 3rd NASA Symposium on VLSI Design

Papers from the symposium are presented from the following sessions: (1) featured presentations 1; (2) very large scale integration (VLSI) circuit design; (3) VLSI architecture 1; (4) featured presentations 2; (5) neural networks; (6) VLSI architectures 2; (7) featured presentations 3; (8) verification 1; (9) analog design; (10) verification 2; (11) design innovations 1; (12) asynchronous design; and (13) design innovations 2