Artur Rydosz

A Micropreconcentrator Design Using Low Temperature Cofired Ceramics Technology for Acetone Detection Applications

We design and manufacture the gas micropreconcentrator in low temperature cofired ceramics (LTCC) technology. The structure is 1.2-mm thick and has lateral dimensions of 25 × 20 mm. It consists of eight layers of LTCC green tapes with spiral-shaped channel filled with absorbing powder. Two heaters covered by the ceramic foils are embedded over and below the channel. The heaters are required for heating the adsorbent to elevated temperatures during its activation and desorption processes. In this paper, we describe the fabrication processes of a micropreconcentrator structure designed for acetone detection applications together with thermal and preconcentration measurements of the device. Commercially available adsorbents: Carboxen-1018, Carboxen-1012, and Carboxen-1003 from Sigma-Aldrich are selected and tested in order to concentrate low levels of acetone. The best concentration factor obtained is 5250.

Gas-Sensing Performance of M-Doped CuO-Based Thin Films Working at Different Temperatures upon Exposure to Propane

Cupric oxide (CuO) thin films are promising materials in gas sensor applications. The CuO-based gas sensors behaved as p-type semiconductors and can be used as part of an e-nose or smart sensor array for breath analysis. The authors present the investigation results on M-doped CuO-based (M = Ag, Au, Cr, Pd, Pt, Sb, Si) sensors working at various temperatures upon exposure to a low concentration of C3H8, which can be found in exhaled human breath, and it can be considered as a one of the biomarkers of several diseases. The films have been deposited in magnetron sputtering technology on low temperature cofired ceramics substrates. The results of the gas sensors’ response are also presented and discussed. The Cr:CuO-based structure, annealed at 400 °C for 4 h in air, showed the highest sensor response, of the order of 2.7 at an operation temperature of 250 °C. The response and recovery time(s) were 10 s and 24 s, respectively. The results show that the addition of M-dopants in the cupric oxide films effectively act as catalysts in propane sensors and improve the gas sensing properties. The films’ phase composition, microstructure and surface topography have been assessed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) methods.

Micropreconcentrator in LTCC Technology with Mass Spectrometry for the Detection of Acetone in Healthy and Type-1 Diabetes Mellitus Patient Breath

Breath analysis has long been recognized as a potentially attractive method for the diagnosis of several diseases. The main advantage over other diagnostic methods such as blood or urine analysis is that breath analysis is fully non-invasive, comfortable for patients and breath samples can be easily obtained. One possible future application of breath analysis may be the diagnosing and monitoring of diabetes. It is, therefore, essential, to firstly determine a relationship between exhaled biomarker concentration and glucose in blood as well as to compare the results with the results obtained from non-diabetic subjects. Concentrations of molecules which are biomarkers of diseases’ states, or early indicators of disease should be well documented, i.e., the variations of abnormal concentrations of breath biomarkers with age, gender and ethnic issues need to be verified. Furthermore, based on performed measurements it is rather obvious that analysis of exhaled acetone as a single biomarker of diabetes is unrealistic. In this paper, the author presents results of his research conducted on samples of breath gas from eleven healthy volunteers (HV) and fourteen type-1 diabetic patients (T1DM) which were collected in 1-l SKC breath bags. The exhaled acetone concentration was measured using mass spectrometry (HPR-20 QIC, Hiden Analytical, Warrington, UK) coupled with a micropreconcentrator in LTCC (Low Temperature Cofired Ceramic). However, as according to recent studies the level of acetone varies to a significant extent for each blood glucose concentration of single individuals, a direct and absolute relationship between blood glucose and acetone has not been proved. Nevertheless, basing on the research results acetone in diabetic breath was found to be higher than 1.11 ppmv, while its average concentration in normal breath was lower than 0.83 ppmv.

A Negative Correlation Between Blood Glucose and Acetone Measured in Healthy and Type 1 Diabetes Mellitus Patient Breath

Background: Exhaled acetone analysis has long been recognized as a supplementary tool for diagnosis and monitoring diabetes, especially type 1 diabetes. It is essential, therefore to determine the relationship between exhaled acetone concentration and glucose in blood. Usually, a direct linear correlation between this both compounds has been expected. However, in some cases we can observe a reverse correlation. When blood glucose was increasing, breath acetone declined. Methods: The breath analysis as a supplementary tool for diagnosing and monitoring diabetes makes sense only in case of utilization of portable analyzers. This need has created a market for gas sensors. However, commercially available acetone gas sensors are developed for measuring samples at several tens part per million. The exhaled acetone concentration was measured using commercial acetone gas sensor (TGS 822, 823 Figaro, Arlington Heights, IL, USA Inc) with micropreconcentrator in low temperature cofired ceramics. The reference analyzer–mass spectrometry (HPR-20 QIC, Hiden Analytical, Warrington, UK) was used. Results: Twenty-two healthy volunteers with no history of any respiratory disease participated in the research, as did 31 patients diagnosed with type 1 diabetes. Respectively, 3 healthy volunteer and 5 type 1 diabetes mellitus subjects with reverse trend were selected. The linear fitting coefficient various from 0.1139 to 0.9573. Therefore, it is necessary to determine the correlation between blood glucose concentrations and under different conditions, for example, insulin levels, as well as correlate the results with clinical tests, for example, Hb1Ac. Conclusions: It is well known that the concentration of acetone is strongly influenced by diet, insulin treatment, and so on. Therefore, much more complex analysis with long-term measurements are required. Thus, presented results should be regarded as tentative, and validation studies with the analysis of clinical test and in a large number of patients, including control groups, need to be carried out.

Performance of Si-Doped WO 3 Thin Films for Acetone Sensing Prepared by Glancing Angle DC Magnetron Sputtering

This paper presents the acetone sensing characteristics of Si-doped (1 at.%) tungsten oxide thin films prepared by glancing angle dc magnetron sputtering. The performance of Si-doped WO3 sensors in the concentration range of 0.04-3.8 ppm at operating temperatures of 150 °C-425 °C has been investigated. Doping of the tungsten oxide film with Si significantly decreases the limit of detection of acetone compared with the pure WO3 sensors reported in the literature. The gas sensors response (S) to acetone was defined as the resistance ratio S = Rair/Rgas, where Rair and Rgas are the electrical resistances for the sensor in air and in gas, respectively. The maximum response measured in this experiment was S = 40.5. Such response was measured in the presence of 3.8 ppm of acetone at an operating temperature of 425 °C using a Si-doped (1 at.%) WO3 thin film deposited at 300 °C and annealed at 300 °C for 4 h in air. The films phase composition, microstructure, and surface topography have been assessed by X-ray diffraction, scanning electron microscope, atomic force microscope, and energy dispersive X-ray spectroscopy methods.

Broadband measurements of reflection coefficient with the use of Butler matrix

A novel application of a 4 × 4 Butler matrix in a broadband reflectometer is presented. The well-known dedicated multiport has been replaced with a standard 4 × 4 Butler matrix with reflective element connected to the one of its ports. It is shown, that properties of such a network allow for the complex reflection coefficient measurements. In order to broaden measurement frequency range, a simple modification of a calibration procedure is proposed. The presented system has been verified experimentally by the measurement of reflection coefficients of three shorted attenuators in frequency range 1 - 5 GHz. The measurements have been compared with ones obtained with the use of commercial VNA, showing good agreement.

Octave-band aperture-stakced microstrip antenna element for wideband antenna arrays

An octave-band aperture-stacked antenna element has been presented. The designed antenna element utilizes two stacked rectangular patches which are excited by aperture coupling with the use of dual-feeding technique along with appropriate matching network. The designed feeding network allows for achieving additional resonance at the lower frequency band, and therefore, the antenna element operates within one frequency octave with improved both flatness of directivity and radiation patterns comparing to the previously described design. The proposed approach has been verified by measurements of the designed antenna element operating in 1.75-3.5 GHz frequency range.

Wide-beam microstrip antenna for application in 24 GHz short-range Doppler sensors

A wide-beam microstrip antenna for applications in short-range Doppler sensors has been developed. Beam widening has been achieved with the use of appropriately fed three radiating patches. To ensure a proper signal distribution along the array, a center radiating element has been designed as an aperture coupled patch fed at its center thorough the slot. Moreover, the center patch serves as a two-way power divider allowing for feeding two outer patches with appropriate amplitudes and phases ensuring simultaneously central symmetry of the antenna which improves radiation pattern.

Leaky-wave antenna with modified metamaterial unit cell for narrowing beam steering bandwidth

A novel unit cell of a composite right/left-handed transmission line has been proposed for application in leaky-wave antennas. It is shown that by the application of an open stub one can freely adjust the radiation frequency range in the right-hand region, and therefore, scanning of the main beam in the desired frequency range can be obtained. The results of theoretical analysis of the unit cell have been shown and confirmed by electromagnetic calculation of the proposed structure.

Nano-thin CuO films doped with Au and Pd for gas sensors applications

The cupric oxide (CuO) thin films are promising materials in gas sensor applications. The CuO exhibits the highest sensitivity for hydrogen sulfide, but it may be also used as a sensor for carbon monoxide or nitrogen dioxide. The sensitivity and long-term stability are critical issues in gas sensor applications. The authors present the results of investigation on nano-thin film of CuO and CuO doped with Au and Pd. The films were deposited in magnetron sputtering technology on LTCC substrates. The results of gas sensor response are presented and discussed. The long-term stability test were performed.