14 research outputs found
Metal oxides based electrochemical pH sensors: Current progress and future perspectives
Electrochemical pH sensors are on high demand in numerous applications such as food processing, health monitoring, agriculture and nuclear sectors, and water quality monitoring etc., owing to their fast response (<10 s), wide pH sensing range (2–12), superior sensitivity (close to Nernstian response of 59.12 mV/pH), easy integration on wearable/flexible substrates, excellent biocompatibility and low cost of fabrication. This article presents an in-depth review of the wide range of MOx materials that have been utilized to develop pH sensors, based on various mechanisms (e.g. potentiometric, conductimetric, chemi-resistors, ion sensitive field effect transistor (ISFET) and extended-gate field effect transistor etc.). The tools and techniques such as potentiometric and electrochemical impedance spectroscopic that are commonly adopted to characterize these metal oxide-based pH sensors are also discussed in detail. Concerning materials and design of sensors for various practical application, the major challenges are toxicity of materials, interfernce of other ions or analytes, cost, and flexibility of materials. In this regard, this review also discusses the metal oxide-based composite sensing (active) material, designs of pH sensors and their applications in flexible/wearable biosensors for medical application are examined to present their suitability for these futuristic applications
Antenna sensing for wearable applications
As wearable technologies are growing fast, there is emerging trend to increase functionality of the devices. Antennas which are primarily component in communication systems can offer attractive route forward to minimize the number of components functioning as a sensing element for wearable and flexible electronics. Toward development of flexible antenna as sensing element, this thesis investigates the development of the flexible and printed sensing NFC RFID tag. In this approach, the sensor measurement is supported by the internal sensor and analog-to-digital convertor (ADC) of the NFC transponder. Design optimisation, fabrication and characterization of the printed antenna are described. Besides, the printed antenna, NFC transponder and two simple resistive sensors are integrated to form a fully flexible sensing RFID tag demonstrating applicability in food and health monitoring.
This thesis also presents development of two antenna sensors by using functional materials: (i) An inductor-capacitor (LC) resonant tank based wireless pressure sensor on electrospun Poly-L-lactide (PLLA) nanofibers-based substrate. The screen-printed resonant tank (resonant frequency of ~13.56 MHz) consists of a planar inductor connected in parallel with an interdigitated capacitor. Since the substrates is piezoelectric, the capacitance of the interdigitated capacitor varies in response to the applied pressure. To demonstrate a potential application of developed pressure sensor, it was integrated on a compression bandage to monitor sub-bandage pressure. (ii) To investigate the realization of sensing antenna as temperature sensor simple loop antenna is designed and in this study unlike the first study that the sensing element was the substrate, the conductive body of the antenna itself is considered as a functional material. In this case, a small part of a loop antenna which originally was printed using silver paste is replaced by Poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT: PSS). The sensing mechanism is based on the resonant frequency shift by varying temperature.
While using functional materials is useful for realization of antenna sensor, another approach also is presented by developing stretchable textile-based microstrip antennas on deformable substrate which can measure joint angles of a human limb. The EM characteristics of the meshed patch antenna were compared with its metallic counterpart fabricated with lithography technique. Moreover, the concept of stretchable UHF RFID-based strain sensor is touched in the final part of this thesis
Sensors for Wireless Body Monitoring Applications
Body monitoring systems have recently drawn great attention to modern electronic consumers due to their various health−care and security applications. However, most of the existing monitoring systems need wire connections that prevent free body movements. Complementary metal−oxide−semiconductor (CMOS) technology based wireless sensor systems need integration of different components that make the device volume and production cost high. In adition, their dependency on on−sensor power source limits the continuous monitoring capability. In the thesis, to demonstrate the feasibility of low cost and simple body monitoring systems, we propose a near−infrared (NIR) photodetector (PD) and a humidity sensor (HS) using low−temperature thin−film processes suitable for large−area electronics application.
For NIR detection, a novel lateral metal−semiconductor−metal (MSM) PD architecture is proposed using low−temperature nanocrystalline silicon (nc−Si) as a NIR absorption layer and organic polyimide (PI) as a blocking layer. Experimental results show that addition of PI layer reduces the dark current (ID) up to 103−105 times compared with the PDs without PI layer. Fabricated devices exhibit a low ID of ~10−10 A, a response time of <1.5 ms, and an external quantum efficiency (EQE) of 35−15% for the 740−850 nm wavelengths of light under 100−150 V biasing conditions. Unlike the standard p−i−n PD, our high−performance lateral PD does not require doped p+ and n+ layers. Thus, the reported device is compatible with industry standard amorphous silicon (a−Si) thin−film transistor (TFT) fabrication process, which makes it promising for large−area full hand biometric imagers suitable for various non−invasive body monitoring applications.
For humidity detection, a 30 mm diameter passive LC (p−LC) HS is formed by joining an octagonal planer inductor and a moisture sensitive interdigital zinc oxide (ZnO) capacitor in series. A PCB reader coil is also designed, which is able to sense the HS from <25 mm distance. The HS reads 30−90% of relative humidity (RH) by interrogating change of the resonance frequency (fR) of the reader−sensor system. The reading resolution is ±2.38%RH and the sensitivity is 53.33−93.33 kHz/1%RH for the above 45% RH measurements. Experimental results show that the proposed HS is operational in a range of 0−75 oC as long as recalibration is performed for a temperature drift of above ±3 oC, which makes it suitable for various promising applications operated at different temperatures. Above all, the presented results are promising for the continuous body monitoring applications to observe the humidity wirelessly without any power source on the sensor
Self-Packaged and Low-Loss Suspended Integrated Stripline Filters for Next Generation Systems
The method in which the frequency spectrum is currently allocated is unsustainable. An increasing number of devices are becoming wireless, overcrowding an already crowded spectrum (e.g., the ISM band). Therefore, future systems will be forced to move to higher frequencies in order to be allocated an unused slice of the spectrum and accumulate the desired/required bandwidth. Furthermore, with the continued desire to implement a multitude of sensors on unmanned aerial vehicles (UAVs), as well as the need for conformal small-cell repeaters for 5G communications, next generation systems will have to achieve unprecedented reductions in size, weight, power, and cost (SWaP-C).
In order for future systems to become practical, several fundamental technological hurdles must be overcome including the development of low loss and highly integrated components used to build next generation systems. The RF/microwave filter is of particular interest, as it is not only crucial for conditioning the signal for transmission and/or digitization, but can also affect critical system parameters based on it's placement in the system. Due to the increased attenuative nature of the environment at microwave frequencies, the systems dynamic range will have to be maximized requiring an exceptionally low loss filter if placed close to the antenna in the receiver (Rx) chain, which is necessary for defense and adaptive/re-configurable systems. While low loss microwave filtering can be easily achieved using waveguide design techniques, it is much more difficult in a highly integrated planar design due to increased radiation and dielectric losses. A promising solution which minimizes these losses and offers a planar solution is the suspended integrated stripline (SISL) filter.
In this research, a low loss fully-board integrated lowpass and highpass filter, using the suspended integrated stripline technology, are designed and studied, pushing the stat-of-the-art in planar filtering technologies. A multi-layer board stack-up, with internally buried hollowed cavities, is used to create the suspended stripline. The embedded filter is accessed through a co-planar waveguide-to-stripline vertical via transition and vice-versa. Simulated and measured results show that insertion losses of less than 1 dB are obtainable including the vertical via transition and associated trace losses. Compared to it's suspended substrate stripline (SSS) predecessor, the SISL filter is one order of magnitude smaller and lighter while achieving identical performance. Beyond the proposed filters, this technological solution can be applied to several other passive microwave components such as couplers, power dividers, and gain equalizers. The capabilities demonstrated in this research will be crucial to the design and integration of modern and next generation systems as it requires no mechanical housing, connectors, or assembly, resulting in a light weight, compact size, and low cost solution
Millimeter-Scale Encapsulation of Wireless Resonators for Environmental and Biomedical Sensing Applications
Wireless magnetoelastic resonators are useful for remote mapping and sensing in environments that are harsh or otherwise difficult to access. Compared to other wireless resonators, magnetoelastic devices are attractive because of their inherently wireless nature, and their ability to operate passively without a power source, integrated circuitry, or antenna.
An open challenge for using miniaturized magnetoelastic resonators is application-tailored encapsulation and packaging. General packaging considerations for magnetoelastic resonators include not only the mechanical design but also electromagnetic transparency, adaptability of form factor with appropriate feature size, and chemical inertness and/or biocompatibility.
In this thesis, the packaging of magnetoelastic resonators is investigated in two contexts: environmental sensing and biomedical sensing. The first context is for tagging and mapping applications in a high temperature (≥ 150°C), high pressure (≥ 10 MPa), corrosive environment, such as a hydraulic fracture branching from a wellbore. This work utilizes for the first time a micro molding process to thermoform liquid crystal polymer (LCP) packages for protecting magnetoelastic resonators. The package is < 10 mm3 and includes micron-scale features to support the resonator and allow it to vibrate with low loss. It has an average shear strength of 60 N, and can endure pressure up to 2000 psi (≈13.8 MPa).
The second context is for implantable magnetoelastic resonators, which are used for sensing biological parameters. These packages must: protect the sensors during deployment through an endoscope, be biocompatible and chemically inert, be able to pass through a complex delivery path, and fit within a limited size. Protecting the resonator during delivery while still allowing interaction with biological fluids is achieved with polymeric packages incorporating features such as a perforated housing and tapered and smoothed edges. This approach also includes features to aid in assembling with plastic stents via polyethylene tethers. The packaged resonator must pass through a complex delivery path without damage due to bending, so the compromise between two architectures – one mechanically flexible (Type F) and one mechanically stiff (Type S) – is evaluated. The primary advantage of the Type F package is the flexibility of the package during the delivery process while that of the Type S package is to maintain a strong signal even when the stent is in a curved bile duct. The length, width, and maximum thickness of the Type F package are 26.40 mm, 2.30 mm and 0.53 mm, respectively. The Type S package has an outer diameter of 2.54 mm, a length of 15 mm, and a maximum thickness of 0.74 mm. The two package types are tested in benchtop flexibility tests, and in vivo and in situ in porcine specimens. The animal tests demonstrate partial functionality of both types of packages, while also indicating that smaller and more elastic package designs are needed.
Remaining in the implantable sensor context, an improved and miniaturized resonator design is explored.
Miniaturizing the resonator accordingly allows miniaturization of the packaging, reducing the impact on the overall functionality of the medical device. The fabricated sensor is 8.25 mm long, 1 mm wide with the largest thickness of 218 μm. The resonant frequency of the resonator is around 173 kHz which is similar to that of a 12.5 mm long ribbon sensor. This resonator design is self-biased, simplifying the packaging and assembly compared to previous designs.PHDElectrical & Computer Eng PhDUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146089/1/jqjiang_1.pd
High Data-Rate, Battery-Free, Active Millimeter-Wave Identification Technologies for Future Integrated Sensing, Tracking, and Communication Systems-On-Chip
RÉSUMÉ Pour de nombreuses applications allant de la sécurité, le contrôle d'accès, la surveillance et la gestion de la chaîne d'approvisionnement aux applications biomédicales et d'imagerie parmi tant d'autres, l'identification par radiofréquence (RFID) a énormément influencé notre quotidien. Jusqu'à présent, cette technologie émergente a été la plupart du temps conçue et développé dans les basses fréquences (en dessous de 3 GHz). D’une part, pour des applications où de courte distances (quelques centimètres) et à faible taux de communications de données sont suffisantes (même préférables dans certains cas), la technologie RFID à couplage inductif qui fonctionne à basse fréquences (LF) ou à haute fréquences (HF) fonctionne très bien et elle est largement utilisée dans de nombreuses applications commerciales. D'autre part, afin d’augmenter la distance de communication (quelques mètres), le débit de données de communication, et ainsi minimiser la taille du tag, la technologie RFID fonctionnant dans la bande d’ultra-haute fréquence (UHF) et aux fréquences micro-ondes (par exemple, 2.4 GHz) a récemment attiré beaucoup d'attention dans le milieu de la recherche et le développement. Cependant, dans ces bandes de fréquences, une bande passante disponible restreinte avec la taille du tag assez large (principalement dominée par la taille d'antenne et de la batterie dans le cas d'un tag actif) sont les principaux facteurs qui ont toujours limité l'évolution de la technologie RFID actuelle. En effet, propulser la technologie RFID dans la bande de fréquences à ondes millimétriques briserait les barrières actuelles de la technologie RFID. La technologie d’identification aux fréquences à ondes millimétriques (MMID) offre plus de bande passante, et permet également la miniaturisation de la taille du tag, car à ces bandes de fréquences, la longueur d’onde est de l’ordre de quelques millimètres, une taille comparable à la taille d’un circuit intégré. L'antenne peut donc être soit intégré sur la même puce (antenne sur puce) ou soit encapsulé dans le même boitier que le circuit intégré. En dotant le tag la capacité de récolter sans fil son énergie à partir d'un signal aux fréquences à ondes millimétriques provenant du lecteur, lui fournissant ainsi l'autonomie énergétique (ainsi éliminant la nécessité d'une batterie et en même temps permettant la miniaturisation du tag), il devient alors possible d'intégrer entièrement tout le tag MMID sur une seule puce y compris les antennes, ce qui aboutira à la mise au point d’une nouvelle technologie miniature (μRFID) fonctionnant à la bande de fréquences à ondes millimétriques.----------ABSTRACT
For countless applications ranging from security, access control, monitoring, and supply chain management to biomedical and imaging applications among many others, radio frequency identification (RFID) technology has tremendously impacted our daily life. So far, this ever-needed and emerging technology has been mostly designed and developed at low RF frequencies (below 3-GHz). For many practical applications where short-range (few centimeters) and low data-rate communications are sufficient and in some cases even preferable, inductively coupled RFID systems that operate over either low-frequency (LF) or high-frequency (HF) bands have performed quite well and have been widely used for practical and commercial applications. On the other hand, in the quest for a longer communication range (few meters), relatively high data-rate and smaller antenna size RFID systems operating over ultra-high frequency (UHF) and microwave frequency bands (e.g., 2.4-GHz) have recently attracted much attention in the research and development community. However, over these RF bands, a restricted available bandwidth together with an undesired tag size (mainly dominated by its off-chip antenna size and battery in the case of active tag) are the main factors that have been limiting the evolution of today’s RFID technology. Indeed, propelling RFID technology into millimeter-wave frequencies opens up new applications that cannot be made possible today.Millimeter-wave identification (MMID) technology is set out to exploit significantly larger bandwidth and smaller antenna size. Over these frequency bands, an effective wavelength is in the order of a few millimeters, hence close to a typical semiconductor (CMOS) die size. The antenna, therefore, may either be integrated on the same chip (antenna-on-chip – AoC) or embedded in the related package (antenna-in-package – AiP). In addition, by equipping the tag with the capability to wirelessly harvest its energy from an incoming millimeter-wave signal, thereby providing energy autonomy without the need of a battery and at the same time allowing miniaturization, it becomes possible to integrate the entire MMID tag circuitry on a single chip. Furthermore, the timely MMID concept is fully compatible with upcoming and future applications of millimeter-wave technology in wireless communications which are being discussed and developed worldwide in research and development communities, such as the internet of things (IoT), 5G, autonomous mobility, μSmart sensors, automotive RADAR technologies, etc
EUROSENSORS XVII : book of abstracts
Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)
Ultra wide-bandwidth micro energy harvester
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 189-197).An ultra wide-bandwidth resonating thin film PZT MEMS energy harvester has been designed, modeled, fabricated and tested. It harvests energy from parasitic ambient vibration at a wide range of amplitude and frequency via piezoelectric effect. At the present time, the designs of most piezoelectric energy devices have been based on high-Q linear cantilever beams that use the bending strain to generate electrical charge via piezoelectric effect. They suffer from very small bandwidth and low power density which prevents them from practical use. Contrarily, the new design utilizes the tensile stretching strain in doubly-anchored beams. The resultant stiffness nonlinearity due to the stretching provides a passive feedback and consequently a wide-band resonance. This wide bandwidth of resonance enables a robust power generation amid the uncertainty of the input vibration spectrum. The device is micro-fabricated by a combination of surface and bulk micro-machining processes. Released devices are packaged, poled and electro-mechanically tested to verify the wide-bandwidth nonlinear behavior of the system. Two orders of magnitude improvement in bandwidth and power density is demonstrated by comparing the frequency response of the system with that of an equivalent linear harvester with a similar Q-factor.by Arman Hajati.Ph.D
Micro/Nano Structures and Systems
Micro/Nano Structures and Systems: Analysis, Design, Manufacturing, and Reliability is a comprehensive guide that explores the various aspects of micro- and nanostructures and systems. From analysis and design to manufacturing and reliability, this reprint provides a thorough understanding of the latest methods and techniques used in the field. With an emphasis on modern computational and analytical methods and their integration with experimental techniques, this reprint is an invaluable resource for researchers and engineers working in the field of micro- and nanosystems, including micromachines, additive manufacturing at the microscale, micro/nano-electromechanical systems, and more. Written by leading experts in the field, this reprint offers a complete understanding of the physical and mechanical behavior of micro- and nanostructures, making it an essential reference for professionals in this field