Horst Demattio

Determination of hydrazines by chip electrophoresis with contactless conductivity detection.

In this report, a new approach for the fast determination of hydrazine compounds (hy) in complex matrices is presented. The experimental protocol is based on poly(methylmethacrylate) (PMMA) microchip separations with contactless conductivity detection using a compact portable device, which integrates all separation and detection components. Three hy (hydrozine (Hy), methylhydrazine (MH), and 1,1‐dimethylhydrazine (UDMH)) were separated within <30 s at a separation voltage of 3.8 kV using a L(−)‐histidine/2‐(N‐morpholinoethanesulfonic acid) (His/MES) buffer (25:50 mM, pH 5.87). The contactless conductivity detection enables detection limits for Hy, MH, and UDMH of 11.9, 35.5, and 337.8 ng/mL, respectively, with linear concentration dependence up to 10 μg/mL. In complex matrices such as soil samples or river water, interferences were eliminated by implementing ultrasound‐assisted headspace single‐drop microextraction of hy under strongly alkaline conditions, using an aqueous drop of His/MES buffer as the extractant phase. The incorporation of this miniaturized sample preparation step led to improved limits of detection for Hy, MH, and UDMH of 6.5, 15.3, and 11.4 ng/mL, respectively. The overall protocol demonstrates a promising approach for interfacing chip electrophoresis with real‐world applications.

Portable integrated capillary-electrophoresis system using disposable polymer chips with capacitively coupled contactless conductivity detection for on-site analysis of foodstuff

We present a compact portable chip-based capillary electrophoresis system that employs capacitively coupled contactless conductivity detection (C4D) operating at 4 MHz as an alternative detection method compared to the commonly used optical detection based on laser-induced fluorescence. Emphasis was put on system integration and industrial manufacturing technologies for the system. Therefore, the disposable chip for this system is fabricated out of PMMA using injection molding; the electrodes are screen-printed or thin-film electrodes. The system is designed for the measurement of small ionic species like Li+, Na+, K+, SO42- or NO3- typically present in foods like milk and mineral water as well as acids e.g. in wine.

Connector-less SiC power modules with integrated shunt - low-profile design for low inductance and low cost

This paper presents the design, manufacture and characterization of connector-less 1200 V SiC MOSFET half-bridge power modules based on AlN DCB substrate. The modules contain four MOSFETs and no external antiparallel diodes. They are rated for a current of 40 A and include a shunt. Static and dynamic measurement results are presented. Multiphysics simulations are used to validate the measured data. The modules show a power path inductance below 3 nH. The power rating of the implemented chip shunt resistors is sufficient for the performed characterizations but requires revision. The switching loss at turn-on is 340 μJ at 23 A, 800 V, the turn-off loss is well below 50 μJ, principally allowing MHz operation in resonant mode.

Towards high sensitive label free DNA detection in lab-on-chip systems

Surprisingly high sensitivity for DNA fragment detection in contactless conductivity measurements by capacitive coupling of HF signals into microfluidic channels was further investigated by impedance spectroscopy. Experimental results indicate the general high conductivity with reduced capacitive behaviour in parallel. It can be also influenced by an electrical DC field inducing DNA alignment in the electrical measuring cell. The results encourage further development of electrical detection methods alternatively to sophisticated and expensive optical detection methods.