Ústav mikroelektroniky

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Single EX-CCCII-Based First-Order Versatile Active Filter
(MDPI, 2024-08-21) Kumngern, Montree; Khateb, Fabian; Kulej, Tomasz
This paper presents a new current-mode first-order versatile active filter employing one extra-x second-generation current controlled current conveyor (EX-CCCII) and one grounded capacitor. The proposed filter can realize first-order filtering functions of a low-pass filter (LPF), high-pass filter (HPF), and all-pass filter (APF) within the same topology with low-input and high-output impedances required for current-mode circuits. This multiple-output EX-CCCII-based filter can provide six transfer functions as both non-inverting and inverting filtering functions of the LPF, HPF, and APF are obtained. The filter also offers electronic control of the pole frequency of all filtering. The proposed current-mode filter can be applied to work as a mixed-mode active filter, namely in the transadmittance-mode (TAM), transimpedance-mode (TIM), and voltage-mode (VM). Each operation mode can provide six transfer functions. The proposed filter was simulated and designed using SPICE and 0.18 mu m CMOS technology. Experimental results using the commercially available integrated circuit AD844 were used to confirm the functionality of the new circuits.
Comparative analysis of surface layer functionality in STM and AFM probes: Effects of coating on emission characteristics
(SLOVAK UNIV TECHNOLOGY, 2024-08-01) Knápek, Alexandr; Allaham, Mohammad Mahmoud; Košelová, Zuzana; Burda, Daniel; Podstránský, Jáchym; Mousa, Marwan S. Mousa; Sobola, Dinara
This study compares different types of scanning probe microscopy (SPM) probes according to the function of the surface layer at the tip apex. Three main types of SPM probes were analyzed: scanning tunneling microscopy (STM) tungsten probes, conductive atomic force microscopy (AFM) probes, and non-conductive AFM probes. The tungsten STM probes were coated with a graphite layer to simulate the effects of carbonization. The tested AFM probes were specifically NenoProbe conductive AFM probes (platinum-coated tip) and Akiyama non-conductive AFM probes coated with gold. The gold coating is intended to improve surface conductivity and help achieve a homogeneous, oxidation-resistant surface. The three samples were measured in a field emission microscope to study their current-voltage characteristics. The obtained current-voltage characteristics were tested and analyzed by the Forbes field emission orthodoxy test, providing the field emission parameters that correlate with the state of the scanning probe tip. In this study, the most important parameter is the formal emission area parameter, which indicates the formal tunneling current density through the probe tip-sample nanogap. For an STM tip, this reflects the size and shape of the region from which electrons tunnel to the sample surface. If this area is larger than expected or desired, it may indicate problems with tip function or tip wear. This information is critical for evaluating the performance and accuracy of the STM tip and can help diagnose problems and optimize its function.
Microfluidics 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, Pavel
This 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.
Compact 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, Martin
Inexpensive 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.
Low-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, Tomasz
This 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.

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