Antenna-Coupled Titanium Microbolometers: Application for Precise Control of Radiation Patterns in Terahertz Time-Domain Systems.

An ability of lensless titanium-based antenna coupled microbolometers (Ti-µbolometers) operating at room temperature to monitor precisely radiation patterns in terahertz time-domain spectroscopy (THz-TDS) systems are demonstrated. To provide comprehensive picture, two different THz-TDS systems and Ti-µbolometers coupled with three different antennas-narrowband dipole antennas for 0.3 THz, 0.7 THz and a log-periodic antenna for wideband detection-were selected for experiments. Radiation patterns, spatial beam profiles and explicit beam evolution along the propagation axis are investigated; polarization-sensitive properties under various THz emitter power ranges are revealed. It was found that the studied Ti-µbolometers are convenient lensless sensors suitable to discriminate and control THz radiation pattern features in various wideband THz-TDS systems.

A THz Receiver with Novel Features and Functionality.

The presented THz receiver is based on an antenna coupled titanium micro-bolometer. A new geometrical design improves the robustness and extends the lifetime of the sensor. A study of sensor lifetime using different biasing currents is presented. The lifetime was verified by several tests and over 1000 operating hours. A new micro-bolometer sensitivity measurement algorithm is presented in the paper and measurement results using the proposed algorithm are shown. The new algorithm was developed to be suitable for ATM production testing. In the paper, a novel feature called "sensitivity boosting" is described, together with its influence on sensitivity and lifetime.

A Differential Monolithically Integrated Inductive Linear Displacement Measurement Microsystem.

An inductive linear displacement measurement microsystem realized as a monolithic Application-Specific Integrated Circuit (ASIC) is presented. The system comprises integrated microtransformers as sensing elements, and analog front-end electronics for signal processing and demodulation, both jointly fabricated in a conventional commercially available four-metal 350-nm CMOS process. The key novelty of the presented system is its full integration, straightforward fabrication, and ease of application, requiring no external light or magnetic field source. Such systems therefore have the possibility of substituting certain conventional position encoder types. The microtransformers are excited by an AC signal in MHz range. The displacement information is modulated into the AC signal by a metal grating scale placed over the microsystem, employing a differential measurement principle. Homodyne mixing is used for the demodulation of the scale displacement information, returned by the ASIC as a DC signal in two quadrature channels allowing the determination of linear position of the target scale. The microsystem design, simulations, and characterization are presented. Various system operating conditions such as frequency, phase, target scale material and distance have been experimentally evaluated. The best results have been achieved at 4 MHz, demonstrating a linear resolution of 20 µm with steel and copper scale, having respective sensitivities of 0.71 V/mm and 0.99 V/mm.

Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues.

A terahertz (THz) imaging system based on narrow band microbolometer sensors (NBMS) and a novel diffractive lens was developed for spectroscopic microscopy applications. The frequency response characteristics of the THz antenna-coupled NBMS were determined employing Fourier transform spectroscopy. The NBMS was found to be a very sensitive frequency selective sensor which was used to develop a compact all-electronic system for multispectral THz measurements. This system was successfully applied for principal components analysis of optically opaque packed samples. A thin diffractive lens with a numerical aperture of 0.62 was proposed for the reduction of system dimensions. The THz imaging system enhanced with novel optics was used to image for the first time non-neoplastic and neoplastic human colon tissues with close to wavelength-limited spatial resolution at 584 GHz frequency. The results demonstrated the new potential of compact RT THz imaging systems in the fields of spectroscopic analysis of materials and medical diagnostics.

Humidity sensors printed on recycled paper and cardboard.

Research, design, fabrication and results of various screen printed capacitive humidity sensors is presented in this paper. Two types of capacitive humidity sensors have been designed and fabricated via screen printing on recycled paper and cardboard, obtained from the regional paper and cardboard industry. As printing ink, commercially available silver nanoparticle-based conductive ink was used. A considerable amount of work has been devoted to the humidity measurement methods using paper as a dielectric material. Performances of different structures have been tested in a humidity chamber. Relative humidity in the chamber was varied in the range of 35%-80% relative humidity (RH) at a constant temperature of 23 °C. Parameters of interest were capacitance and conductance of each sensor material, as well as long term behaviour. Process reversibility has also been considered. The results obtained show a mainly logarithmic response of the paper sensors, with the only exception being cardboard-based sensors. Recycled paper-based sensors exhibit a change in value of three orders of magnitude, whereas cardboard-based sensors have a change in value of few 10s over the entire scope of relative humidity range (RH 35%-90%). Two different types of capacitor sensors have been investigated: lateral (comb) type sensors and modified, perforated flat plate type sensors. The objective of the present work was to identify the most important factors affecting the material performances with humidity, and to contribute to the development of a sensor system supported with a Radio Frequency Identification (RFID) chip directly on the material, for use in smart packaging applications. Therefore, the authors built a passive and a battery-supported wireless module based on SL900A smart sensory tag's IC to achieve UHF-RFID functionality with data logging capability.

Mobile wireless monitoring system for prehospital emergency care.

BACKGROUND: Latest achievement technologies allow engineers to develop medical systems that medical doctors in the health care system could not imagine years ago. The development of signal theory, intelligent systems, biophysics and extensive collaboration between science and technology researchers and medical professionals, open up the potential for preventive, real-time monitoring of patients. With the recent developments of new methods in medicine, it is also possible to predict the trends of the disease development as well the systemic support in diagnose setting. Within the framework of the needs to track the patient health parameters in the hospital environment or in the case of road accidents, the researchers had to integrate the knowledge and experiences of medical specialists in emergency medicine who have participated in the development of a mobile wireless monitoring system designed for real-time monitoring of victim vital parameters. Emergency medicine responders are first point of care for trauma victim providing prehospital care, including triage and treatment at the scene of incident and transport from the scene to the hospital. Continuous monitoring of life functions allows immediate detection of a deterioration in health status and helps out in carrying out principle of continuous e-triage. In this study, a mobile wireless monitoring system for measuring and recording the vital parameters of the patient was presented and evaluated. Based on the measured values, the system is able to make triage and assign treatment priority for the patient. The system also provides the opportunity to take a picture of the injury, mark the injured body parts, calculate Glasgow Coma Score, or insert/record the medication given to the patient. Evaluation of the system was made using the Technology Acceptance Model (TAM). In particular we measured: perceived usefulness, perceived ease of use, attitude, intention to use, patient status and environmental status. METHODS: A functional prototype of a developed wireless sensor-based system was installed at the emergency medical (EM) department, and presented to the participants of this study. Thirty participants, paramedics and doctors from the emergency department participated in the study. Two scenarios common for the prehospital emergency routines were considered for the evaluation. Participants were asked to answer the questions referred to these scenarios by rating each of the items on a 5-point Likert scale. RESULTS: Path coefficients between each measured variable were calculated. All coefficients were positive, but the statistically significant were only the following: patient status and perceive usefulness (ß = 0.284, t = 2.097), environment (both urban a nd rural) and perceive usefulness (ß = 0.247, t = 2.570; ß = 0.329, t = 2.083, respectively), and perceive usefulness and behavioral intention (ß = 0.621 t = 7.269). The variance of intention is 47.9%. CONCLUSIONS: The study results show that the proposed system is well accepted by the EM personnel and can be used as a complementary system in EM department for continuous monitoring of patients' vital signs.

A Microbolometer System for Radiation Detection in the THz Frequency Range with a Resonating Cavity Fabricated in the CMOS Technology.

BACKGROUND: The THz sensors using microbolometers as a sensing element are reported as one of the most sensitive room-temperature THz detectors suitable for THz imaging and spectroscopic applications. Microbolometer detectors are usually fabricated using different types of the MEMS technology. The patent for the detection system presented in this paper describes a method for microbolometer fabrication using a standard CMOS technology with advanced micromachining techniques. The measured sensitivity of the sensors fabricated by the patented method is 1000 V/W at an optimal frequency and is determined by the performance of a double-dipole antenna and quarter-wavelength resonant cavity. METHOD: The paper presents a patented method for fabrication of a microbolometer system for radiation detection in the THz frequency range (16). The method is divided into several stages regarding the current silicon micromachining process. Main stages are fabrication of supporting structures for micro bridge, creation of micro cavities and fabrication of Aluminum antenna and Titanium microbolometer. Additional method for encapsulation in the vacuum is described which additionally improves the performance of bolometer. The CMOS technology is utilized for fabrication as it is cost effective and provides the possibility of larger sensor systems integration with included amplification. At other wavelengths (e.g. IR region) thermistors are usually also the receivers with the sensor resistance change provoked by self-heating. In the THz region the energy is received by an antenna coupled to a thermistor. Depending on the specific application requirement, two types of the antenna were designed and used; a narrow-band dipole antenna and a wideband log-periodic antenna. RESULTS: With method described in the paper, the microbolometer detector reaches sensitivities up to 500 V/W and noise equivalent power (NEP) down to 10 pW/√Hz. Additional encapsulation in the vacuum improves its performance at least by a factor of 2, therefore the sensitivity reaches approximately 1000 V/W and NEP down to 5 pW/√Hz. The thermal response time of bolometer is 0.5 µs. The thermistor biasing current drops with its resistance (defined by microbolometer active area), but the sensitivity rises. Typical value of biasing current is 300 µA at 680 Ω of resistance, where the sensitivity reaches highest level. Air pressure decrease highly influences the sensitivity due to lower thermal dissipation to surrounding air. The sensitivity is therefore doubled when packaged in the high vacuum (0.1Pa). CONCLUSION: The main advantage of the presented approach is that the detection devices can be fabricated by a standard silicon micromachining process. Their overall dimension is defined by the receiving antenna and they do not need any additional optic source for the operation. They are robust and appropriate for mass production and can be easily embedded or merged with other vision system in use. The developed microbolometer is highly sensitive, its noise is low and it operates at a room temperature with no additional cooling system at a normal atmospheric pressure. The output of the THz detector connected to a discrete low-noise amplifier increases the total sensitivity up to 106 V/W with no impact on the noise equivalent power of 5 pW/√HZ.

Monitoring, control and diagnostics using RFID infrastructure.

This work demonstrates the developed application for disinfection control by the sensing of chemical agents. The objective was to develop an Automatic Disinfectant Tracker (ADT) that would verify the disinfection of the hands of nurses, doctors, staff, patients, and visitors in hospitals within a required time frame. We have successfully investigated the development of hand disinfection control mechanisms and demonstrated two approaches, both based on the wireless Ultra-High-Frequency-based Radio-Frequency Identification (UHF-RFID) technology. The 100 % efficacy of detecting propanol and ethanol concentration was achieved by using the static disinfectant control (SDC-ADT) method. The time domain response provides an accurate determination of their performance in practice simply by measuring the applied disinfectant concentration and the duration of application. The present paper resulted from the measurements of a capacitive chemical sensor fabricated in the Laboratory for Microelectronics, (LMFE) and on measurements, based on a commercially available resistive type of sensor. A graphic user interface (IDS-GUI) is designed to successfully set the logger parameters and display the results.