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- ItemMicrofluidics chips fabrication techniques comparison(NATURE PORTFOLIO, 2024-11-20) Liu, Xiaocheng; Sun, Antao; Brodský, Jan; Gablech, Imrich; Lednický, Tomáš; Vopařilová, Petra; Zítka, Ondřej; Zeng, Wen; Neužil, PavelThis study investigates various microfluidic chip fabrication techniques, highlighting their applicability and limitations in the context of urgent diagnostic needs showcased by the COVID-19 pandemic. Through a detailed examination of methods such as computer numerical control milling of a polymethyl methacrylate, soft lithography for polydimethylsiloxane-based devices, xurography for glass-glass chips, and micromachining-based silicon-glass chips, we analyze each technique's strengths and trade-offs. Hence, we discuss the fabrication complexity and chip thermal properties, such as heating and cooling rates, which are essential features of chip utilization for a polymerase chain reaction. Our comparative analysis reveals critical insights into material challenges, design flexibility, and cost-efficiency, aiming to guide the development of robust and reliable microfluidic devices for healthcare and research. This work underscores the importance of selecting appropriate fabrication methods to optimize device functionality, durability, and production efficiency.
- ItemThermodynamics of Crystals Formation and Growth in a Sessile Droplet(Cell Press, 2024-05-09) Zhu, Hanliang; Zhang, Yue; Lu, Haiyang; Feng, Jianguo; Yan, Qi-Long; Brodský, Jan; Gablech, Imrich; Neužil, PavelAccurately detecting subtle thermodynamics during crystallization and associated water evaporation processes, especially around seed formation, has been challenging. Here, we report a method to investigate the complex energy changes during these simultaneous endothermic and exothermic events. We employ an open-space microcalorimeter, coupled with optical observation using a microscope equipped with a camera for real-time monitoring. This method reveals crystal formation by observing energy changes and simultaneously visualizing the sample. The concentration influence for potassium chloride crystallization is analyzed, including energy released and the evaporation thermodynamics using isothermal microcalorimetry. We also monitor the energy dissipation during crystallization, showing an 4.2 s period for potassium chloride crystal seed formation with a released energy of 11.9 J. This method can potentially reshape strategies for controlled crystallization across diverse industrial and laboratory settings. Extending beyond potassium chloride, our findings shed light on broader crystallization dynamics, paving the way for innovations in materials and energy sciences.
- ItemLow-Voltage Low-Power Differential Difference Current Conveyor Transconductance Amplifier and Its Application to a Versatile Analog Filter(IEEE, 2024-07-12) Kumngern, Montree; Khateb, Fabian; Kulej, TomaszThis paper presents a new low-voltage low-power differential difference current conveyor transconductance amplifier (DDCCTA). The proposed DDCCTA utilizes a multiple-input gate-driven MOS transistor (MIGD-MOST) operating in the subthreshold region to achieve low supply voltage, minimum number of MOS differential pairs and minimum power consumption. To show the advantages of the proposed DDCCTA, it was used to realize a versatile analog filter. The filter uses three DDCCTAs, two grounded capacitors, and two grounded resistors to realize 65 transfer functions of low-pass, high-pass, band-pass, band-stop, and all-pass filters by appropriately selecting the input and output terminals without changing the filter topology. The filter also has the advantages of high-input impedance, which is ideal for voltage-mode circuits, independent control of the natural frequency and quality factor, and the ability to electronically tune the natural frequency. The proposed DDCCTA and versatile analog filter were designed and simulated using SPICE with TSMC 0.18 mu m CMOS technology to verify the new circuits. The proposed filter uses +/- 0.5 V of supply voltage and 103 mu W of power.
- ItemCompact 3D-Printed Unit for Separation of Simple Gas Mixtures Combined with Chemiresistive Sensors(MDPI, 2024-07-06) Zvonková, Magdaléna; Adámek, Martin; Skowronková, Nela; Dlabaja, Stepan; Matyáš, Jiří; Jaššo, Miroslav; Adámková, Anna; Mlček, Jiří; Salek, Richardos Nikolaos; Búran, MartinInexpensive chemiresistive sensors are often insufficiently selective as they are sensitive to multiple components of the gas mixture at the same time. One solution would be to insert a device in front of the sensor that separates the measured gas mixture and possibly isolates the unwanted components. This study focused on the fabrication and characterization of a compact unit, which was fabricated by 3D printing, for the separation and detection of simple gas mixtures. The capillary, the basic part of the compact unit, was 4.689 m long and had a diameter of 0.7 mm. The compact unit also contained a mixing chamber on the inlet side and a measuring chamber with a MiCS-6814 sensor on the outlet side. Mixtures of ethanol and water at different concentrations were chosen for characterization. The measured calibration curve was found to have a reliability of R2 = 0.9941. The study further addressed the elements of environmental friendliness of the materials used and their sustainability.
- ItemEffect of Heat Stress on the Antioxidant Activity of Boar Ejaculate Revealed by Spectroscopic and Electrochemical Methods(ESG, 2015-06-24) Horký, Pavel; Tmejová, Kateřina; Kenšová, Renáta; Cernei, Natalia Vladimirovna; Kudr, Jiří; Ruttkay-Nedecký, Branislav; Sapáková, Eva; Adam, Vojtěch; Kizek, RenéAn effect of heat stress on antioxidant activity and overall quality of boar ejaculates was monitored. The samples of boar ejaculates were divided into two groups according to ejaculate quality. In the group A, regarding antioxidant activity a decreased value of N,N-dimethyl -1,4-diaminobenzene method by 71 %, an increase in 2,2-diphenyl-1-picrylhydrazyl method by 104 %, and decrease in superoxide dismutase activity by 39 % was determined. Results of the metal content were as follows decrease in levels of copper by 60 % and zinc by 52 %. Also decreases in metallothionein content by 64 %, and in pH by 11 % were recorded. In the group B, in antioxidant activity again a decreased value of DMPD by 68 %, and an increase in DPPH by 207 % was recorded. In addition reduced levels of copper by 78 %, zinc by 30 %, metallothionein by 64 %, and value of pH by 11 % were determined. The results show that heat stress induces an increase in protection against oxidative stress; in addition, levels of metallothionein, zinc and copper in the boar ejaculates in both groups are decreased when compared to day 0.