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In its main definition, piezoelectrets are polymeric structures with electric charged internal cavities. The bipolar-trapped charges form macro-dipoles that can be mechanically deformed, thus presenting a high piezoelectric coefficient in the order of hundreds of pC/N. Such results outperform most of the traditional piezoelectric polymers. As piezoelectrets can be manufactured by different methods, some of the techniques allow the inner cavities to be geometrically controlled, therefore providing some degree of freedom in the piezoelectric behavior. This report provides a description of the most relevant methods, starting with a brief introduction of piezoelectret origin and reaching recent achievements in piezoelectret production, such as additive manufacturing (3D printing). Materials that are frequently employed in piezoelectret fabrication and methods for improving their characteristics are also presented.

The imagiology using Narrow Band Light (NBL) is widely employed in detection of mucosa's premature changes of gastrointestinal tract, while taking advantage of light spectral features by enhancing the vascular structures without the application of any type of dye. NBL uses two specific spectral bands centered in blue (415 nm) and green (540 nm). Despite their greater advantages, this technique is not available on intra-corporal imagiology devices yet. Thus, this paper presents a low-cost method to adapt such devices without the need to develop specific and expensive LEDs (Light-Emitting Diodes) centered at 415 nm and 540 nm. The method combines optical filters with commercial LEDs to provide transmitted light with the desired peaks at 415 nm and 540 nm. Two optical filters were designed and fabricated, using 7 thin-films layers of SiO2 and TiO2 deposited by RF sputtering. The measurements showed that the transmitted light through the filters presented relative transmittance peaks located at 414 nm and 542 nm wavelengths with relative transmittances of 31% and 62% and FWHM (Full-Width-Half-Maximum) of 17 nm and 29 nm, respectively. The measurements also showed significant relative transmittances located at NBL central wavelengths of 415 and 540 nm with 30% and 60%.

Ceroid neuronal lipofuscinosis (CLN) is a rare group of autosomal recessive neurodegenerative diseases that cause developmental delay and seizures. Herein, we present a case of a 7-year-old girl who referred for magnetic resonance imaging (MRI) following cognitive impairment and seizures. MRI was performed demonstrating some usual findings, and, surprisingly, a normal-sized cerebellum. This case draws attention to not hold to just the classical imaging presentation in order to suspect some leukodystrophy.

This study demonstrates that the electron beam irradiation of materials, typically used in characterization measurements, could be employed for advanced fabrication, modification, and functionalization of composites. We developed irradiation equipment using an electron beam irradiation source to be applied in materials modification. Using this equipment, the formation of a thick Ag film on the Ag3PO4 semiconductor is carried out by electron beam irradiation for the first time. This is confirmed by various experimental techniques (X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy) and ab initio molecular dynamics simulations. Our calculations demonstrate that, at the earlier stages, metallic Ag growth is initiated preferentially at the (110) surface, with the reduction of surface Ag cations forming metallic Ag clusters. As the (100) and (111) surfaces have smaller numbers of exposed Ag cations, the reductions on these surfaces are slower and are accompanied by the formation of O2 molecules.

In this paper, a microwave biosensor with unprecedented sensitivity based on encoded pulse propagation and microfluidics is theoretically investigated and experimentally demonstrated. The structure consists of a double-spiral transmission line on FR4 substrate electromagnetically coupled to a copper coiled capillary tube above it. The working principle for improved sensitivity consists of propagating an encoded sequence of short pulses (Walsh-Hadamard spreading code with variable temporal length) in a recirculating manner so that the pulses are deformed both due to dispersive and time-delay effects. Once the recirculation is finished, the energy of the code at the sensor output is calculated, providing an indicator directly related with the analyte concentration. The experimental results demonstrate the improved sensitivity of this sensor approach for the case of glucose with 2.9 mg/ml resolution. Furthermore, we demonstrate the potential of this technology as a sensor platform by investigating other chemical compounds such as isopropyl alcohol (IPA) and acetone with a sensitivity of 20% of the volume. Finally, the outstanding performance, both in terms of accuracy and sensitivity, situates the present multi-purpose approach within the state-of-the-art of microwave (bio)chemical sensors.

The non-invasive intracranial pressure (NIICP) method based on a skull deformation has been proven to be a significant tool for an assessment of the intracranial pressure (ICP) and compliance. Herein, we present the development and characterization of a novel wireless sensor that uses this method as its working principle and was designed to be easy to use, to have a high resolution, and to achieve a good accessibility. Initially, a brief review of the physiology fundamentals of the ICP and the historic evolution of the NIICP method are mentioned. The sensor architecture and the rationale for the chosen components are then presented, aiming to ensure nanometer displacement measurements, the conversion of analog resolution to digital at a high speed, the fewest amount of distortion, wireless communication, and signal calibration. The NIICP signal has a typical amplitude of $5~\mu \text{m}$ , and thus a resolution of at least 1% of this amplitude is required for an NIICP waveform analysis. We also demonstrate a 40-nm resolution of the sensor using a nanometric displacement test system that can also respond dynamically for NIICP signals from 50 to 180 bpm without any significant distortion (maximum deviation of P2/P1 ratio of 2.6%). The future applications for this device are broad and can enhance a clinical assessment of the intracranial dynamics.

This work focuses on acoustic analysis as a way of discriminating mineral oil, providing a robust technique, immune to electromagnetic noise, and in some cases, depending on the applied sensor, a low-cost technique. Thus, we propose a new method for the diagnosis of the quality of mineral oil used in electrical transformers, integrating a ferroelectric-based hydrophone and an acoustic transducer. Our classification solution is based on a supervised machine learning technique applied to the signals generated by an in-home built hydrophone. A total of three statistical datasets entries were collected during the acoustic experiments on four types of oils. The first, the second, and third datasets contain 180, 240, and 420 entries, respectively. Eighty-four features were considered from each dataset to apply to two classification approaches. The first classification approach is able to distinguish the oils from the four possible classes with a classification error less than 2%, while the second approach is able to successfully classify the oils without errors (e.g., with a score of 100%).

This work presents a capacitive modulator design and modeling of a new waveguide architecture using silicon and poly-si technologies. We use a methodology involving the entire lumped-type modulator design process, from the optical design to the small-signal RF analysis. By means of geometric and physical parameters adjustments, the trade-offs among several figures of merit are analyzed in this paper. Due to the waveguide configuration, it is shown that the modulator can improve the trade-off between $V_{\pi }$ and bandwidth compared to the state-of-the-art for this kind of device. For instance, the best combinations are $V_{\pi }\simeq$ 1 V @ 20.4 GHz and $V_{\pi }$ = 5.7 V @ $\sim$ 31 GHz, with equivalent optical losses of 3 dB and 1.1 dB, respectively.

The exponential demand for bandwidth in data centers is on high alert with the increase in data traffic. In this scenario, the design of optical modulators is crucial for the continuous evolution of communication systems. For data center interconnect (DCI) applications, this mean that modulators should offer high bandwidth and low optical loss. In addition, devices must operate with low power consumption and be compatible with complementary metal–oxide–semiconductor (CMOS) processes for low-cost and large-scale manufacturing. These facts show the importance of advancement in Silicon (Si) modulators solutions, since they have the potential to fulfill all these requirements. However, designing a device that meets all these requirements at the same time is still challenging, because there are several trade-offs problems involved for which different Silicon modulators types are not yet able to solve. In this context, this paper reviews the challenges in Silicon photonics (SiPh) modulators for data center interconnect applications.

A Silicon (Si) modulator and a design methodology using a system-oriented numerical approach are proposed. The main contributions of this work are to provide a Silicon modulator as an alternative solution for intra-data center interconnect (DCI) applications and a single figure-of-merit (FOM) for the modulator design, which takes as input the main device parameters (modulation efficiency ( V π × L ), optical loss, and electro-optical bandwidth ( f 3 d B )) and provides a global optical system optimization. By using a numerical approach, the modulator physical parameters are analyzed according to system performance metrics such as the required receiver sensitivity to reach a target bit error rate (BER), and the required transmitter launch power. A capacitive Silicon device and a 4-level pulse amplitude modulation (PAM-4) system simulator is presented. The results show an efficient modulator ( V π = 3.5 V ) with high bandwidth ( f 3 d B > 38 GHz ), which is promising for data centers solutions, where power consumption is critical and high-speed is required.

This paper presents a system for characterization of thermoelectric generators (TEGs) for energy harvesting. This system can monitor and characterize up to three TEGs simultaneously and it is comprised by two main electronic circuits: The first one is composed by twelve input channels being three for reading voltage, three for reading current by making use of instrumentation amplifiers (reference ACS712) and six thermocouples for signal reading (

This paper proposes a Flexible Infrastructure for Dynamic Power Control (FIDPC) of Electric Vehicle (EV) Battery Chargers. This infrastructure dynamically adjusts the EV battery charger current, according to the power demand of the home wherein the vehicle is plugged. An infrastructure was implemented to validate this proposal. Such infrastructure is composed by an EV battery charger and a communication system based on a Radio Frequency interface. The battery charger has nominal power of 3.6 kVA and operates with sinusoidal current and unitary total power factor, while the RF interface provides continuous data flow to the battery charger with information about the home total current consumption (rms value). Experimental tests were performed under realistic conditions to validate the concept behind the proposed FIDPC. These tests served to assess the behavior of the EV battery charger with dynamic power control on a single-phase, 230 V, 16 A, 50 Hz residential electrical installation. The experimental results confirm the quick time response of the FIDPC even when working under heavy home load variations., This work was supported by the Fundacao para a Ciencia e Tecnologia (FCT) through Project PEst-UID/CEC/00319/2013. The work of V. Monteiro was supported by the FCT agency through a doctoral scholarship under Grant SFRH/BD/80155/2011. The review of this paper was coordinated by Dr. D. Cao.

This paper presents a capacitive modulator design and modeling using poly-si and silicon technologies. We propose a methodology involving the entire modulator design process, from the optical design, charge distribution calculation and small-signal RF analysis. Thus, in the case of silicon photonics modulators, the paper proposes means to optimize the trade-offs among several figures of merit. It is shown that high bandwidth operation (>30 GHz) can be achieved by sacrificing a little the modulation efficiency. info:eu-repo/semantics/publishedVersion

Transformers are one of the most important equipment found in electrical power systems. Thus, their status must be constantly monitored to avoid critical failures. The analysis of the dissolved gas (DGA) in the oil is one of the most important technique to detect short-circuits and partial discharges. However, this technique has a serious drawback to get the percentage of water absorbed by the oil, requiring other kind of predictive technique. In this context, this paper presents a technique to detect the water content in oils, which uses ultrasound measurement. The measurement results showed that after the frequency scan, the best results for determining the percentage of water in insulating oils were obtained at frequencies around 5MHz. These preliminary results revealed very promising.

This paper reports on the design and simulation of a bioamplifier, which can amplify bio-signals in the range of 1Hz up to 10kHz while rejecting DC offsets generated at the interface between electrodes and tissue. The fully-integrated bio-amplifier was designed in the 2 metals/1 poly 0.7μm CMOS process from the on-semiconductor. The bioamplifier shows a gain of 39.8dB in the range from 100Hz to 6kHz. The area consumed by the amplifier is around 0.36mm2 of chip area, and the power consumption of the system is around 37μW from a 5V voltage supply.

This paper presents an optical sensor for angular measurements to perform precise tracking of the sun's incident angle in a photovoltaic system. This microdevice was designed using a 0.18μm CMOS technology from TSMC. The microdevice is composed by a matrix of photodiodes and their respective readout electronics. A set of microstructures were used to resolve the angles of rotation by measuring the angle of incident light in the microdevice. These microstructures were fabricated on top of the photodiodes using the same CMOS process. Simulations and experimental setup showed the possibility of taking measurements from the angles between −60 to 60 degrees.

This paper presents an up/down converter double-balanced Gilbert cell mixer for frequencies of 433, 870 and 928 MHz in the ISM band (industrial, scientific and medical). This mixer was designed with the on-semiconductor (former AMIS) 0.7μm CMOS technology. The Gilbert cell topology was selected due to its good figure of merit (FOM), which takes into account parameters such as the conversion gain (CG), isolation between the input ports, linearity and the noise figure. This mixer provides frequency translation by means of a true multiplication on four quadrants. The simulations showed a total power consumption of 3mW from a power supply of 5V, a CG of 10.5dB, an input referred third-order input intercept point (IIP3) of 29.72dBm and an input referred 1-dB compression point (IP1dB) of 13.15dBm. This paper also presents a comparison for the three bands in order to confirm the scalability and suitability of the mixer implemented. The target application of this mixer is to provide communication to/from intra-corporal communication devices.

This paper presents few developments on CMOS microelectronics for the implementation of photonic modules on endoscopic capsules (ECs). The first microelectronic system was developed with the goal to allow photodynamic therapy (PDT) on ECs. This first system was designed in the 2-metals/1-poly 0.7μm CMOS process from the on-semiconductor. The second development is an optical sensor designed for spectroscopy analysis on ECs from diffuse reflectance light originated in the gastrointestinal tissue. This second system was designed in the mixed-signal/RF 0.18μm CMOS general process from the Taiwan Semiconductor (TSMC).

This paper presents optical filters for narrow-band imaging on medical devices. Two optical filters were designed to provide an extremely narrow passband around the 415 nm (blue) and 540 nm (green) wavelengths using the Fabry-Perot phenomenon. Each filter is composed by successive thin-film layers of dielectric materials of titanium dioxide (TiO2) and silicon dioxide (SiO2). The TiO2 and SiO2 that compose the thin-films were fully characterized by ellipsometry applied within the 250–1700 nm wavelength range. The optical performance of the blue NBI optical filter (415 nm) was also measured. These filters were developed to integrate with light emitting diodes (LED) to provide the desired narrow-band imaging (NBI) bands on medical devices.

This paper presents a flexible sensor based on photonics for measuring strain, curvatures and vibrations. This flexible sensor is composed by a Fiber Bragg Grating (FBG) embedded into polydimethylsiloxane (PDMS). The selected FBG resonates at the wavelength of 1552.37 nm and is embedded before the curing for enabling a strong adhesion between both components. Few prototypes were fabricated and characterized. The measurements showed a maximum strain sensitivity of ≈400 pm per 1% elongation, revealing to be sensitive to strain/bending forces and vibration. The measurements allowed to establish a predictable response for both static and dynamic behavior, corresponding to a resolution of ≈88 pm per curvature degree. This flexible sensor also allowed high strain cycles and presented the linear behavior of ≈14 pm °C-1 over the temperature range 20-110 °C. The high-simplicity of the fabrication process results on low-cost with high-degree of reproducibility of their characteristics.

This paper presents a flexible thin-film (FTF) composed by a photovoltaic (PV) cell, a flexible solid-state rechargeable battery and power management electronics. A flexible printed circuit board (fPCB) was used for providing physical support to the electronics and to the battery, whereas a PDMS (polydimethylsiloxane) layer was used for providing mechanical adhesion between the PV cell and the fPCB. The high elasticity of the PDMS makes this material an excellent candidate for adapting two materials with different thermal expansions (fPCB and PV). The physical measurements showed a prototype with a thickness in the range 1.52 ± 0.10 mm, 10 g of weight and 37 × 114 mm of size. The electrical measurements showed ability to provide an output voltage of 3.8 V in a continuously form under these conditions: the PV providing DC power for solar irradiations higher than 6 W m−2, and the battery providing DC power for solar irradiations above bellow 6 W m−2 (value that has emerged during the twilight between sunset and dusk).

This paper analyses the influence of the coating process in the optical efficiency of replicated Moire´ Diffraction Gratings (MDGs), which are applied on real field applications for measuring both the surface displacements and strains. The Moire´ diffraction technique is an experimental full-field, non-contact and high resolution optical method, which can reveal to be very useful in extreme harsh environments. The optical efficiency of the replicated MDGs plays an important role in the quality of the experimental measurements. Two processes were used to obtain the metallic coatings: sputtering and aluminum vaporization. A good coatings quality with high optical efficiency was achieved for both processes (e.g., 17%–28%). However, for the replicated gratings a slight decrease in the optical efficiency was found (e.g., 14%–21%). The MDGs were successfully used for the experimental measurements of displacement and strains in a single lap joint. The measurements also showed that high quality of measurements allowed the identification of unbounded regions., This work was fully supported by the Portuguese Foundation for the Science and Technology (FCT) under the financial Grant FCOMP-01-0124-FEDER-010236, through Project Ref. FCT/PTDC/EME-PME/102095/2008.

Three-dimensional (3D) printing is a feasible solution for fast prototyping with precision in micrometer range. On the other hand, piezoelectrets are polymeric films with internal cavities, which has been electrically charged, resulting in a material with piezoelectric behavior. In the present paper, both, technology and concept were combined to produce structures with well-defined cavities and electromechanical properties. 3D printing can be performed in large range of materials, however for piezoelectret production the polymer must be electrically stable as in electrets. For this study, acrylonitrile butadiene styrene (ABS) was chosen as the base structural material and different voided structures were prepared. Results from pressure dependence and temporal stability are here presented.

This paper presents the fabrication technology of microlenses maintaining a high reproducibility of their characteristics with low cost. The objective of microlenses is to be integrated into imagers in CMOS technology to allow stereoscopic vision. The fabricated microlenses form cylindrical arrays to be placed above the optical filters and photodetectors, in order to potentiate stereoscopic vision and at the same time maximizing the color fidelity. An array of optical filters centered at the primary colors will enable a multicolor usage. The AZ4562 material was the photoresist selected for fabricating the microlenses. The cylindrical shape is obtained by reflowing the photoresist using the hot-plate technique.

This paper presents a photonic system based on Fiber Bragg Gratings (FBGs) for application to wearable garments. The objective is spanning the FBGs over the whole area of the garments for acting as sensing elements. The FBGs are embedded on a polychloroethanediyl (polyvinyl chloride, commonly abbreviated as PVC) carrier in order to increase their sensitivity to strains and for improving the simultaneous acquisition of respiratory and cardiac frequencies with only one FBG sensor. The global structure comprising FBGs and carrier allow high strain cycles and at the same time present linear behavior with the temperature, 17 pm º C -1. The measurements show a stable structure for temperatures up to 100 º C. This brings excellent perspectives for measuring the temperature with high accuracy and range. A set of tests were done by subjecting the FBG/carrier structure (with FBG stretched and no curves) to strains up to 1.2 mm, and it was also observed a linear behaviour: e.g., displacements of 0.8 pm εμ-¹. Behind its sensing enhancement operation, the carrier makes easy to mount the sensing structures., (/0025/2008)

In this paper is presented a fabrication process for obtaining refractive microlenses arrays with high reproducibility and low cost. This process was specifically optimized for the AZ4562 photoresist. Functional prototypes of microlenses arrays with dimensions in the range of 30 m, 4.9 mm and 5 m for width, length and thickness, respectively, were fabricated and tested. The pre-thermal reflow spacing between adjacent isosceles trapezoids is 1.35-5.43 m, from bottom to top, respectively. This separation allows the photoresist to reflow and join the adjacent microlens creating a consistent and homogeneous array., This work and Rui Pedro Rocha are fully supported by the Portuguese Foundation for Science and Technology under the project FCT/PTDC/EEA-ELC/109936/2009 and the financial grant SFRH/BD/33733/2009, respectively. The authors would also like to acknowledge Dr.-Ing Christian Koch from MicroChemicals GmbH for the technical support.

This project is sponsored by ADI with the reference NFCE – FCOMP-01-0202-FEDER-005358 and also sponsored by IVV Automação Lda., This paper presents an active magnetic platform for guiding endoscopic capsules (EC) inside the human body. The system is composed by an external permanent magnet (EPM) made of neodymium Nd-Fe-B rare with a high-level of magnetization (N48) for allowing a maximum magnetic field of 1.5 T. Inside of a standard EC [1] (with dimensions of 26 mm of length and 11 mm in diameter) is placed a small internal permanent magnet (IPM) made of neodymium with cylindrical shape, diameter of 3 mm, length of 8 mm and magnetization of N48. Remote control of ECs allows reliable diagnostic of the esophagus with the required time duration (not possible with the standard EC). The possibility to stop and to rotate the EC will provide detailed images of the esophagus, stomach and small bowel. Also, increasing the speed of the EC will save power battery that will allow the use of a battery with reduced dimensions and opening space for the placement of the IPM inside of the EC.

This paper presents a stereoscopic image sensor in CMOS technology. The proposed sensor allows the acquisition of stereoscopic images with a resolution of 1024×1024 pixels per channel and a targeted signal-to-noise ratio and dynamic-range of 60 dB. An array of microlenses (fabricated with post-processing techniques) separates the left and right optical channels to form the stereoscopic image. An array of optical filters tuned to the primary colors allows a multicolor usage. The fill factor is increased by applying the 1.5 transistor (1.5 T) concept and photodiodes with octagonal shapes. The reflow method applied to the AZ9260 thick photoresist allows the fabrication of microlenses with high reproducibility

This paper presents radio-frequency (RF) microsystems (MSTs) composed by low-power devices for use in wireless sensors networks (WSNs). The RF CMOS transceiver is the main electronic system and its power consumption is a critical issue. Two RF CMOS transceivers with low-power and low-voltage supply were fabricated to operate in the 2.4 and 5.7GHz ISM bands. The measurements made in the RF CMOS transceiver at 2.4GHz, which showed a sensitivity of -60dBm with a power consumption of 6.3mW from 1.8V supply. The measurements also showed that the transmitter delivers an output power of 0dBm with a power consumption of 11.2mW. The RF CMOS transceiver at 5.7GHz has a total power consumption of 23mW. The target application of these RF CMOS transceivers is for MSTs integration and for use as low-power nodes in WSNs to work during large periods of time without human operation, management and maintenance. These RF CMOS transceivers are also suitable for integration in thermoelectric energy scavenging MSTs.

Thin-film solid-state rechargeable batteries on silicon are ideal power sources for microsystems applications, where a high level of integration is required. This paper presents a lithium solid-state thin-film battery for integration in stand-alone microsystems. The thin-films were deposited by direct current (DC) and radio-frequency (RF) reactive sputtering techniques. The materials of the battery includes SnO2, Li3PO4N and LiCoO2 as anode, electrolyte and cathode, respectively. The SnO2 gives the battery a maximum storage capacity of 781 mAhg−1, the LiCoO2 can maintain a capacity of 140 mAhg−1. The two materials used as anode and cathode with the Li3PO4N as electrolyte can obtain an output voltage in the range 3-4.2 V.

The performance of minimally invasive devices for medical inspection could be significantly improved by an amplification imaging module (AIM), which can be considered a highly miniaturized digital microscope to image in-vivo tissue in real-time. An example is the magnification provided by the bulky conventional endoscope that allows the recognition of the affected mucosa with higher precision as compared to normal endoscopic inspection and enables the differentiation of affected tissue from healthy surroundings. Therefore, an AIM that can be integrated in very small medical devices as optical tool for ophthalmologic, thoracic and gastro endoscopic diagnostic will be a tremendous breakthrough. An especially microfabricated 200 µm thick PDMS lens, limiting the total length of the optical system to about 11 mm plus 4 mm for the lateral lens assembly (suitable to include in a 30 mm×11 mm cylindrical medical device) was assembled with more 3 commercial lenses. The height, radius of curvature and focal length of the PDMS lens can be changed by design and were selected to meet the specified system performance, which is set by the imaging requirements. The fabrication process was based in a hanging droplet approach, which is a very low-cost and effective method for obtaining lens with the desired properties. Several analyses were performed showing good performance of the lens system: a paraxial magnification of 14 times was achieved with a Modulation Transfer Function (MTF) around 37% at 50 lp/mm and maximum distortion about 1.83%.

This paper presents an acquisition system for measuring and characterization of thermoelectric generators (TEGs) for energy harvesting purposes on wireless sensors networks (WSNs). This system can monitor and characterize up to three TEGs simultaneously and is comprised of two main electronic circuits: the first one is composed of 12 input channels being three for reading voltage, three for reading current by making use of instrumentation amplifiers (ACS712), and six thermocouples for signal reading (

Early detection of gastrointestinal (GI) can cers is one of most important concerns in medical field. Its detection at the earliest stage is crucial to increase the patient survival chances. Optical signals extraction and analysis, specifically diffuse reflectance and intrinsic fluorescence, may impr ove the ability to detect GI dysplasia, once some morphological and biochemical changes on the tissues (related with early cancer progre ssion) can modify these signals’ shape and intensity. The project under th is paper aims to develop a chip - sized spectros copy microsystem for the early detection of GI cancer. This paper presents the characterization of silicon photodiodes (n+/p - epilayer type) fabricated in a standard 0.7 μm CMOS process, with different dimensions. The main goal is to conclude which photodio de must be fabricated for the microsystem implementation, taking into account its capacity to extract the signals in the relevant spectral band (350 nm – 750 nm), not comprising the microsystem dimensions. With this study , it can be conclude d that the suit able photodiodes for the detection of those spectroscopic signals are the ones with 125 × 125 μm 2 or 100 × 100 μm 2 active area , once their quantum efficiency varies between 20% and 55%, approximately, above 450 nm. In spite of the low photodiod es quantum efficiency (lower than 20%) below 450 nm, the viability of using the 100 × 100 μm 2 photodiode to extract the diffuse reflectance signal, between 350 nm and 750 nm, was proven using a test phantom representative of a GI tissue., This work is funded by FEDER funds through the "Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, projects reference COMPETE: FCOMP-01-0124-FEDER-020241 and FCOMP-01-124-FEDER-037291 (PEst-C/FIS/UI0607/2013) and by FCT – Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. S. Pimenta thanks the FCT for the SFRH/BD/87605/2012 PhD grant.

This paper presents a Low-Cost Flexible-Platform (LCFP) for measuring and characterizing photodetectors. This LCFP can characterize simultaneously up to 16 photodetectors and is composed by two main electronic circuit boards: a Transimpedance Amplifier Board (TIAB) and a Development Board (DevB). The TIAB was designed and optimized to reduce the noise increase, in order to convert photocurrents into voltages and at the same time, allowing the gain selection between one of the three values: 1 × 105 (low-gain, LG), 1 × 106 (medium-gain, MG) and 1 × 107 (high-gain, HG). The DevB is composed by 16 analog inputs, 54 digital inputs/outputs and an internal Analog to Digital Converter (ADC). It is possible to digitally change the Upper End Voltage (UEV) of the ADC's range to voltages below +5 V. The DevB can convert into the digital domain each one of the 16 analog signals from the TIAB with a resolution of 48.9 nA, 4.9 nA and 0.5 nA for the highest value of UEV (+5 V) and when either LG, MG or HG is selected, respectively. The measured data can be acquired in real-time with LabView software, which allows the real-time monitoring of the photocurrents for individual elements in the photodetector both through a numeric and graphical display. The light intensity can be defined by 8 digital outputs allowing 256 light intensity increments/steps from 0 to a maximum defined (by the lamp's manufacturer) light intensity. This LCFP can be used in industry to make quality control, e.g., when different test conditions are applied to the optical sensors/photodetectors and the user/customer need to quickly check if the response or performance is acceptable or resulted on any significant drifts. All these features combined with the low-cost under 1400 € makes this LCFP a suitable tool to quickly evaluate the performance of optical sensors/photodetectors., This work was sponsored by the Brazilian agency National Council of Scientific Research (Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq) under the grant 400110/2014-8: Ciência sem Fronteiras/Chamada de projetos MEC/MCTI/CAPES/CNPQ/FAPS – Bolsa Pesquisador Visitante Especial (PVE) 2014.

This paper presents two approaches in microlenses (MLs) and photodiodes (PDs) integration for improving the light-photocurrent conversion. The first one consists in fabricating MLs with AZ4562 photoresist on a glass substrate: The integration of MLs with a focal length of 170 µm on a 150 µm thickness glass substrate aligned on top of a 240 µm square CMOS photodiode resulted in a decrease of ≈38% for the light-current conversion under white light. In the second approach the MLs were fabricated also with AZ4562 in 24-5 µm width-thickness (at the apex) on top of a 240 µm and 24 µm square CMOS photodiodes. The results showed an increase in light-current conversion in both cases: The 240 µm photodiode presented an increase of ≈2.6% and ≈5.2% under white and red light respectively, while the 24 µm photodiode presented an increase of ≈2.3% and ≈14.5% also under white and red light respectively.

This letter presents a microlenses (MLs) fabrication process for enhancing the photocurrent (PC) generation efficiency of photodiodes (PDs). The concept was demonstrated with a plano-convex spherical ML fabricated directly on top of a PD. The PDs are of type n+/p-substrate junction fabricated in a standard CMOS process. The base and sag height of the MLs measure 26 and 5 μm, respectively. The PC generation was measured inside a dark chamber under normally incident red light illuminance both with and without the ML on top of the PD. The illuminance was linearly incremented from 0 to 2000 lux. The ML forces more light to impinge into the PDs active area and, therefore, promotes more PC generation. The measurements show that the PD generates, at an approximately constant rate of 14%, more PC with the MLs than without the MLs., This work was supported in part by the Doctoral MIT-Portugal Scholarship under Grant SFRH/BD/33733/2009, in part by the Project FCT/PTDC/EEAELC/109936/2009, and in part by the Portuguese Foundation for Science and Technology.

This paper presents the statistical analysis applied into the shape of microlenses (MLs) for validating the high-reproducibility feature of their fabrication process. The MLs were fabricated with the AZ4562 photoresist, using photolithography and thermal reflow processes. Two types of MLs arrays were produced for statistical analysis purposes: the first with a cross-sectional diameter of 24 μm and the second with a cross-sectional diameter of 30 μm, and both with 5 μm spacing between MLs. In the case of 24 μm diameter arrays, the measurements showed a mean difference in diameter of 2.78 μm with a standard deviation (SD) of 0.22 μm (e.g., 2.78 ± 0.22 μm of SD) before the reflow, and 2.34 ± 0.35 μm of SD after the reflow. For the same arrays, the mean difference in height obtained was, comparatively to the 5.06 μm expected, 0.76 ± 0.10 μm of SD before the reflow and 1.91 ± 0.15 μm of SD after the reflow, respectively. A mean difference in diameter of 2.64 ± 0.41 μm of SD before the reflow, and 1.87 ± 0.34 μm of SD after the reflow was obtained for 30 μm diameter MLs arrays. For these MLs, a mean difference in height of 0.71 ± 0.12 μm of SD before the reflow and 2.24 ± 0.24 μm of SD after the thermal reflow was obtained, in comparison to the 5.06 μm of height expected to obtain. These results validate the requirement for reproducibility and opens good perspectives for applying this fabrication process on high-volume production of MLs arrays., This work was fully supported by the Portuguese Foundation for Science and Technology under the project FCT/ PTDC/EEA-ELC/109936/2009.

This paper presents optical filters for integration on stereoscopic image sensors. The filters must cover each one of primary colors within the visible, in order to yield a passband around the respective wavelengths. Dielectric materials based on SiO2 and TiO2 were used due to their compatibility with silicon. The best simulation with only 3 dielectric layers resulted in optical filters with full width at half maximum (FWHMs) of 79, 95 and 124 nm and central wavelengths of 456, 529 and 605 nm, respectively.

This work was fully supported by the Algoritmi’s Strategic Project UI 319-2011-2012, under the Portuguese Foundation for Science and Technology grant Pest C/EEI/UI0319/2011.

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The optical techniques are a powerful tool on situations where either the physical contact or invasive techniques for evaluation are not suitable. Vehicle environments constitute an application field for the optical techniques and are the focus of this chapter. In order to reinforce this kind of techniques, it must be clarified that the idea to manipulate the light backs to the second century before our age, when Archimedes planned to destroy enemy ships using a solar heat ray with an array of actuators to change the shape of a mirror (Bifano T., 2011). Therefore, the field of photonics is the one that offers the possibility to achieve one of the greatest realizations and applications because the light is present in all aspects of the human life and our way of living is impossible without light (Carmo J. P. et al., 2012a). Optical measurement systems are also suitable for harsh monitorization because they are non-contact and full-field techniques. This is the case of Moiré Interferometry, which is used for many optoelectronic applications as displacement measurements (Wronkowski L., 1995), evaluation of microelectronics devices deformation (Xie H. et al., 2004), optical communications (Chen L. et al., 2000), strain measurements with Fiber Bragg Grattings, FBGs, (Silva A. F. et al., 2011) and spectrography (Kong S. H. et al., 2001). In this context, it must be noted that the recent nuclear disaster in Fukushima, Japan, confirms the need of tighter security measures be done within harsh environments (which includes the automobiles) in order to increase both the safety of people and the reliability of vehicles’ parts.

This paper presents a sensing electronic-free wearable solution for monitoring the body kinematics. The measuring of the knee movements, flexion and extension, with the corresponding joint acting as the rotation axis is shown as working principle. The proposed sensing system is based on a single optical Fiber-Bragg Grating (FBG) with a resonance wavelength of 1547.76 nm. The optical fiber with the FBG is placed inside a new polymeric foil composed by three flexible layers which facilitates its placement in the anatomic parts under investigation while maintaining full sensing capabilities. The way the device is placed in the specific body part to be measured enables the clear detection of the movements in respect to the joint. The proposed solution was tested using a prototype that was built to evaluate the device under different condition tests and also to assess the system's consistency. The designed and fabricated system demonstrates clear advantages in medical fields like physical therapy applications as optical fiber is not affected by electromagnetic interference nor does the system needs complex and expensive electronic systems and mechanical parts. Another advantage is the possibility to measure, record and evaluate specific mechanical parameters of the limbs' motion. Patients with bone, muscular and joint related health conditions, as well as athletes, are within the most important end-user applications.

This chapter presents a wireless interface for intra-vehicle communications (data acquisition from sensors, control, and multimedia) at 5.7 GHz. As part of the wireless interface, a RF transceiver was fabricated in the UMC 0.18 µm RF CMOS process and when activated, it presents a total power consumption of 23 mW with the voltage-supply of 1.5 V. This allows the use of only a coin-sized battery for supplying the interface. The carrier frequency can be digitally selectable and take one of 16 possible frequencies in the range 5.42-5.83 GHz, adjusted in steps of 27.12 MHz. These multiple carriers allow a better spectrum allocation and at the same time will improve the channel capacity due to the possibility to allow multiple accesses with multiple frequencies.

An automobile was seen as a simple accessory of luxury in the early years of the past century. Therefore, it was an expensive asset which none of the common citizen could afford. It was necessary to pass a long period and waiting for Henry Ford to establish the first plants with the series fabrication. This new industrial paradigm makes easy to the common American to acquire an automobile, either for running away or for working purposes. Since that date, the automotive research grown exponentially to the levels observed in the actuality. Now, the automobiles are indispensable goods; saying with other words, the automobile is a first necessity article in a wide number of aspects of living: for workers to allow them to move from their homes into their workplaces, for transportation of students, for allowing the domestic women in their home tasks, for ambulances to carry people with decease to the hospitals, for transportation of materials, and so on, the list don’t ends. The new goal pursued by the automotive industry is to provide electric vehicles at low cost and with high reliability. This commitment is justified by the oil’s peak extraction on 50s of this century and also by the necessity to reduce the emissions of CO2 to the atmosphere, as well as to reduce the needs of this even more valuable natural resource. In order to achieve this task and to improve the regular cars based on oil, the automotive industry is even more concerned on doing applied research on technology and on fundamental research of new materials. The most important idea to retain from the previous introduction is to clarify the minds of the potential readers for the direct and indirect penetration of the vehicles and the vehicular industry in the today’s life. In this sequence of ideas, this book tries not only to fill a gap by presenting fresh subjects related to the vehicular technology and to the automotive engineering but to provide guidelines for future research. This book account with valuable contributions from worldwide experts of automotive’s field. The amount and type of contributions were judiciously selected to cover a broad range of research. The reader can found the most recent and cutting-edge sources of information divided in four major groups: electronics (power, communications, optics, batteries, alternators and sensors), mechanics (suspension control, torque converters, deformation analysis, structural monitoring), materials (nanotechnology, nanocomposites, lubrificants, biodegradable, composites, structural monitoring) and manufacturing (supply chains). We are sure that you will enjoy this book and will profit with the technical and scientific contents. To finish, we are thankful to all of those who contributed to this book and who made it possible. info:eu-repo/semantics/publishedVersion

The introduction of nanotechnology opened new horizons previously unattainable by thermoelectric devices. The nano-scale phenomena began to be exploited through techniques of thin-film depositions to increase the efficiency of thermoelectric films. This chapter reviews the fundamentals of the phenomenon of thermoelectricity and its evolution since it was discovered in 1822. This chapter also reviews the thermoelectric devices, the macro to nano devices, describing the most used techniques of physical vapor depositions to deposit thermoelectric thin-films. A custom made deposition chamber for depositing thermoelectric thin films by the thermal co-evaporation technique, where construction issues and specifications are discussed, is then presented. All the steps for obtaining a thermoelectric generator in flexible substrate with the custom deposition chamber (to incorporate in thermoelectric microsystems) are described. The aim of thermoelectric microsystem relays is to introduce an energy harvesting application to power wireless sensor networks (WSN) or biomedical devices. The scanning probe measuring system for characterization of the thermoelectric thin films are also described in this chapter. Finally, a few of the prototypes of thermoelectric thin films (made of bismuth and antimony tellurides, \({\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}\), and \({\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}\), respectively) obtained by co-evaporation (using the custom made deposition chamber) and characterized for quality assessment are dealt with. All the issues involved in the co-evaporation and characterization are objects of analysis in this chapter.

This paper presents a low-cost technology for fabricating optical filters arrays tuned for the primary colors. The fabrication process presented in this paper is intended for directly printing the optical filters into a transparent flexible substrate (acetate). The target application of these optical filters is for enabling the acquisition of multicolor stereoscopic images with a sensor made in CMOS technology.

Solid-state thermoelectric generators (TEGs) based on the Seebeck effect to convert temperature gradients, ΔT [K], into electrical energy are being used in an increased number of stand-alone microsystems applications. These generators are composed by at least one pair of p- and n-type thermoelectric elements with high figures-of-merit, ZT, to perform such a conversion. The exact behavior knowledge of generators is mandatory in order to decide the most suitable for the target application. The focus of this paper is to present a methodology to characterize thermoelectric generators, by measuring their behavior for different types of loads. The measurements were done with the help of commercial thermoelectric generators (thermoelectric modules TEC1-12707) and a measurement setup composed by a controlled hot-plate, a controlled cooling fan (above an heat dissipator), a set of two thermistors for measuring the temperature, a personal computer with the data acquisition board model NI USB-6009 and the LabView software from National Instruments for acquiring the measures and for controlling both the hot-plate and the cooling fan. The thermoelectric modules TEC1-12707 was selected due to its compact size (e.g., 40 mm × 40 mm) and because it can withstand temperatures up to 450 K without degrading the quality of measurements. A SPICE model for thermoelectric modules TEC1-12707 was also obtained: an open-circuit voltage of Vopen = 53.17 × ΔT [mV] and an internal resistance of R0 = 3.88 Ω with a tolerance of ΔRint = 0.13 Ω such that Rint = R0 ± ΔRint = 3.88 ± 0.13 Ω. The measurements done under the maximum output power delivery condition (for the maximum temperature gradient of ΔT = 51 °C) resulted in the maximum output power of Pout = 500 mW, as well as in the output current and voltage of Iout = 357 mA and Vout = 1.40 V, respectively. The load resistance of 3.92 Ω (Vout/Iout) is also in accordance with the measurements because it is located in the range [μ − σ, μ + σ] Ω, where μ = R0 = 3.88 Ω and σ = ΔRint = 0.13 Ω. An Agilent multimeter model 34410A with 6½ digits was used for measuring the voltages at the TEG’s output and the respective currents.

This paper presents a frequency synthesizer for the frequency of 2.4 GHz, which were designed to present a reduced level of reference frequency spurs. Parts of the synthesizer were fabricated in a standard 0.18 μm CMOS process, whose architecture is based on a Phase-Locked Loop (PLL) with an integer divider in the feedback loop and was designed to work with a voltage supply of only 1.8 V. Some building blocks are reused thus the novelty of this paper is presenting a PLL with two new blocks for reducing the magnitude of spurs of the process, e.g., a sample-and-hold circuit and a quantizer circuit (with N quantizing levels). The PLL behaviour was simulated for a few number of levels — N={32, 64, 128} — and for a variety of loop-filters. As showed by the simulations, the quantizations provide an additional reduction of the reference-frequency spurs into the output of the PLL. Moreover, the locking time is kept low even after including the two new circuit blocks in the loop