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Mohamed S.A.,Albert Ludwigs University of Freiburg | Manoli Y.,Institute For Mikro Und Informationstechnik
Proceedings - IEEE International Symposium on Circuits and Systems | Year: 2015

A voltage-controlled oscillator (VCO) with low phase noise and low power dissipation for sub-harmonic mixing is proposed. A cross-coupled negativeresistance circuit with nMOS transistors in the feedback is adopted to suppress high-order harmonics. According to this proposed structure, low phase noise can be achieved under low power dissipation. The VCO chip including a cross-coupled differential buffers (not shown in this work) is implemented in 0.13μm CMOS process under a supply voltage of 1.2V and consumes a total power of 0.5 mW. The measured results show that the VCO with integrated buffers at 1 MH offset frequency has a phase noise of -138 dBc/Hz. The proposed design has a wide tuning range of 380-420 MHz under the tuning voltage of 0-1.2V power supply voltage. © 2015 IEEE.

Kliche K.,Institute For Mikro Und Informationstechnik | Kattinger G.,Institute For Mikro Und Informationstechnik | Billat S.,Institute For Mikro Und Informationstechnik | Shen L.,Institute For Mikro Und Informationstechnik | And 3 more authors.
IEEE Sensors Journal | Year: 2013

We present a microelectromechanical systems-based sensor for the thermal detection of changes of gas mixtures such as the CO2 concentration in air that is of interest in air conditioning climate control within buildings. Key properties of the system are low power consumption (<10mW) and high long-term stability through the absence of moving or consumptive components. The used sensor chip has three silicon-microwires (thermistors) surrounded by the gas mixture to be analyzed. A centered wire (heater) is supplied with sinusoidal heating power. This induces a thermal response via the surrounding gas to measurement wires (detectors) located in different distances from the heater. The phase shift between heating power and induced thermal responses at the detectors is analyzed and depends on the thermal properties of the gas. After calibration, the sensor is able to quantify the concentration of an individual component within a mixture of different but known gas components. This is demonstrated by measuring the CO2 concentration in N 2CO2 mixtures with a resolution of 0.2% at constant pressure and temperature. © 2001-2012 IEEE.

Vashist S.K.,Institute For Mikro Und Informationstechnik | Vashist S.K.,Albert Ludwigs University of Freiburg | Lam E.,National Research Council Canada | Hrapovic S.,National Research Council Canada | And 2 more authors.
Chemical Reviews | Year: 2014

Biosensing and diagnostic platforms with high sensitivity, specificity, and fast response time are based on immobilized biomolecules such as antibodies (Abs), aptamers, enzymes, nucleic acids, receptors, and whole cells for the detection of target analytes. Such sensing biomolecules should be bound to the surface of a signal transducer with a required specific chemical, electrical, or optical property. The biological recognition event generates a quantifiable signal, which is equated to the amount or concentration of the analyte. APTES can be deposited on solid materials, electrode materials, nanomaterials, and nanocomposites under variable conditions of concentration, solvent, temperature, and time. In addition, curing conditions such as air/heat drying might be necessary depending upon the intended application. Pertinent information on the thickness, morphology, and conformation of the APTES layer reported in the literature is often different and conflicting.

Vashist S.K.,Institute For Mikro Und Informationstechnik | Vashist S.K.,Albert Ludwigs University of Freiburg | Schneider E.M.,University of Ulm | Luong J.H.T.,University College Cork
Analyst | Year: 2014

This article describes a highly-sensitive surface plasmon resonance (SPR)-based immunoassay (IA) for human fetuin A (HFA), a specific biomarker for atherosclerosis and hepatocellular carcinoma. The assay is based on a novel immobilization procedure that simply involves the dilution of an anti-HFA capture antibody (Ab) in 1% (v/v) 3-aminopropyltriethoxysilane (APTES), followed by its dispensing on a KOH-treated gold (Au)-coated SPR chip and incubation for 30 min. The developed SPR IA detected 0.3-20 ng mL-1 of HFA with a limit of detection and sensitivity of 0.7 ng mL-1 and 1 ng mL -1, respectively. The highly-simplified Ab immobilization procedure is also 5-fold more rapid than conventional procedures. It leads to the leach-proof binding of the capture Ab, which means that the developed SPR IA is highly cost-effective, as the Ab-bound SPR chip could be reused for many repeated HFA IAs after regeneration with 10 mM glycine-HCl, pH 2.0. The Ab-bound SPR chip, stored at 4 °C, lost only 18% of its original activity after 4 months. For the detection of HFA spiked in diluted human whole blood and plasma, the results obtained by the developed SPR IA agreed well with the commercial HFA sandwich ELISA. This journal is © the Partner Organisations 2014.

Kalkandjiev K.,Albert Ludwigs University of Freiburg | Riegger L.,BioFluidix GmbH | Kosse D.,Institute For Mikro Und Informationstechnik | Welsche M.,Albert Ludwigs University of Freiburg | And 4 more authors.
Journal of Micromechanics and Microengineering | Year: 2011

We investigate TMMF photopolymer as a cost-efficient alternative to glass for the leak-tight sealing of high-density silicon microchannels. TMMF enables low temperature sealing and access to structures underneath via lamination and standard UV-lithography instead of costly glass machining and anodic bonding. TMMF is highly transparent and has a low autofluorescence for wavelengths larger than 400 nm. As the photopolymer is too thin for implementing bulky world-to-chip interfaces, we propose adhesive bonding of cyclic olefin copolymer (COC) modules. All materials were tested according ISO 10993-5 and showed no cytotoxic effects on the proliferation of L929 cells. To quantify the cost efficiency of the proposed techniques, we used an established silicon/Pyrex nanoliter dispenser as a reference and replaced structured Pyrex wafers by TMMF laminates and COC modules. Thus, consumable costs, manpower and machine time related to sealing of the microchannels and implementing the world-to-chip interface could be significantly reduced. Leak tightness was proved by applying a pressure of 0.2 MPa for 5 h without delamination or crosstalk between neighboring microchannels located only 100 μm apart. In contrast to anodic bonding, the proposed techniques are tolerant to surface inhomogeneities. They enable manufacturing of silicon/polymer microfluidics at lower costs and without compromising the performance compared to corresponding silicon/glass devices. © 2011 IOP Publishing Ltd.

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