Jiri Kroutil

Detection of Breathing

Acoustic signals originate by the flow of air through the trachea during breathing. These signals are possible to pick-up by microphone. This paper describes a method of the breathing detection based on the sensing of acoustic signals in trachea. Parameters of the breathing, detection inspiration and expiration and apnoea pause are possible to determine from these signals. This method is simple and easy to use, portable and provides an accurate measurement and seems to be well suited for use as a modern breathing monitor.

Fabrication of Diamond Based Quartz Crystal Microbalance Gas Sensor

Synthetic diamond has remarkable properties comparable with natural diamond and hence is a very promising material for many various applications (sensors, heat sink, optical mirrors, cold cathode, tissue engineering, etc.). Nowadays, deposition of diamond films is normally employed in chemical vapor deposition (CVD) usually at high temperatures (800900 °C), what limit its application to high melting substrates. Gravimetric (mass) sensors belong to the major categories of chemical sensors and the most common type of mass sensor is the bulk acoustic quartz crystal microbalance (QCM). This contribution deals with a nanocrystalline diamond (NCD) growth from the H2/CH4/CO2 gas mixture at low temperature (400 °C) by pulsed linear antenna microwave plasma system on 10 MHz circular AT-cut quartz resonators substrate. Gas sensor based on the NCD-coated QCM was developed for detection of ammonia (NH3) at room temperature. Measurements not only confirmed the functionality of this first published NCD-coated QCM sensor, but in addition its sensitivity was twofold to a virgin QCM sensor with a gold active layer.

Respiration monitoring during sleeping

The respiration belongs among basic vital functions and the knowledge of their parameters and quality is necessary in medicine. The research is leading to the methods, which are inconvenienced patients. These methods are important for monitoring respiration towards observation quality sleeping or The Sudden Infant Death Syndrome (SIDS). This paper contains an overview of the methods for the respiration monitoring used not only in practice of medicine but till now developed.

Gas-sensing behaviour of ZnO/diamond nanostructures

Microstructured single- and double-layered sensor devices based on p-type hydrogen-terminated nanocrystalline diamond (NCD) films and/or n-type ZnO nanorods (NRs) have been obtained via a facile microwave-plasma-enhanced chemical vapour deposition process or a hydrothermal growth procedure. The morphology and crystal structure of the synthesized materials was analysed with scanning electron microscopy, X-ray diffraction measurements and Raman spectroscopy. The gas sensing properties of the sensors based on i) NCD films, ii) ZnO nanorods, and iii) hybrid ZnO NRs/NCD structures were evaluated with respect to oxidizing (i.e., NO2, CO2) and reducing (i.e., NH3) gases at 150 °C. The hybrid ZnO NRs/NCD sensor showed a remarkably enhanced NO2 response compared to the ZnO NRs sensor. Further, inspired by this special hybrid structure, the simulation of interaction between the gas molecules (NO2 and CO2) and hybrid ZnO NRs/NCD sensor was studied using DFT calculations.

Precise beat frequency evaluation circuit for multi-oscillators QCM gas detectors

Presented work deals with crystal oscillators that can be used as a quartz crystal microbalance (QCM) gas sensor. There are presented two basic oscillators that are very common in literature. The oscillators were put into practice and tested in the gas chamber with different crystals of basic frequency 10 MHz. There were tested clean crystal resonators and resonators coated by a sensitive layer. Frequency response of the oscillators is usually very small and it is comparable with the effects such as temperature change or crosstalk in the evaluation circuit. The evaluation circuit thus must be designed carefully. Main goal of this paper is comparison of two basic designs of the oscillators and presentation of the precise evaluation circuit with minimal crosstalk and reverse transmission in signal ways.

Acoustic method for respiratory monitoring

This paper describes a method of the respiration monitoring based on the sensing of acoustic signals in trachea. Further, the article describes method for signal processing of the acoustic signals. The respiration belongs among basic vital functions and the knowledge of their parameters and quality is necessary in medicine. The research is leading to the methods, which are inconvenienced patients. Monitoring of respiration is important for monitoring respiration towards observation quality sleeping or The Sudden Infant Death Syndrome (SIDS).

Gas analyzer for quick indicative measurements

The article describes the design and realization of the gas analyzer using 4 types of gas sensors — catalytic, electrochemical, semiconductor and infrared sensor. The analyzer is intended for quick orientation measuring the presence of gas. The analyzer includes basic parts — the sensor part, the evaluation and control part, the display and the output actuator part. The analyzer is designed for easy modification of its connection to different types of chemical sensors. The sensor part includes a chemical sensor, an EEPROM and a temperature sensor. The type of the used sensor sets the operation mode of the both part — evaluation and control part. Actuators on the output are ready to control the security elements (ventilation, alarm, etc.). The display shows the basic information — gas concentration, temperature, and more. Evaluation and control part includes microprocessor, memory for long-term data, signaling LEDs, push buttons.

Characterization of gas sensor with polyaniline film

The aim of the paper is to present results of design gas sensor with different form of polyaniline active layer for toxic gases detection. Sensing of toxic gases is very important in many applications. Automotive, defence, aerospace, agriculture, chemical industry, medicine, environmental, food and drink are many important markets for chemical and biological sensors. The advantages of resistive sensors are easy fabrication, simple operation and low production cost. Using of polymer film causes that this sensor is not required heating of active layer. This leads to reduce power consumption. Active layer is operated at room temperature.

The Study of Graphene Gas Sensor

The graphene is suitable for gas sensing applications for its two dimensional char-acter which gives the best possible ratio between sensor surface and volume. The interactionbetween graphene surface and gas molecules can signicantly change the graphene layer trans-port properties. Therefore graphene can serve as a sensitive layer in a gas sensor. This work isconcentrated on the analysis of the conductivity of graphene layer exposed to dierent gases(NH3, CO2 ...). Together with the electrical measurement on the interdigital graphene sensora simulation based on quantum atomistic approach has been performed. We used ATK toolkitby Quantuwise based on density functional theory (DFT) models. The exchange-correlationpotential is approximated within the generalized gradient approximation (GGA). The trans-port properties of the electrode-device- electrode geometry were calculated by means of non-equilibrium Greens function formalism as implemented in ATK. Experimental conductivitychanges are compared with the simulation results.