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96 results on '"Mathwig, Klaus"'

58. Bisecting Microfluidic Channels with Metallic Nanowires Fabricated by Nanoskiving

Author

Kalkman, Gerard, Zhang, Yanxi, Monachino, Enrico, Mathwig, Klaus, Kamminga, MacHteld, Pourhossein, Parisa, Oomen, Pieter E, Stratmann, Sarah A, Zhao, Zhiyuan, van Oijen, Antoine M, Verpoorte, Ellsabeth, Chiechi, Ryan, Kalkman, Gerard, Zhang, Yanxi, Monachino, Enrico, Mathwig, Klaus, Kamminga, MacHteld, Pourhossein, Parisa, Oomen, Pieter E, Stratmann, Sarah A, Zhao, Zhiyuan, van Oijen, Antoine M, Verpoorte, Ellsabeth, and Chiechi, Ryan

Abstract

This paper describes the fabrication of millimeter-long gold nanowires that bisect the center of microfluidic channels. We fabricated the nanowires by nanoskiving and then suspended them over a trench in a glass structure. The channel was sealed by bonding it to a complementary poly(dimethylsiloxane) structure. The resulting structures place the nanowires in the region of highest flow, as opposed to the walls, where it approaches zero, and expose their entire surface area to fluid. We demonstrate active functionality, by constructing a hot-wire anemometer to measure flow through determining the change in resistance of the nanowire as a function of heat dissipation at low voltage ( < 5 V). Further, passive functionality is demonstrated by visualizing individual, fluorescently labeled DNA molecules attached to the wires. We measure rates of flow and show that, compared to surface-bound DNA strands, elongation saturates at lower rates of flow and background fluorescence from nonspecific binding is reduced.

Published
2016

61. pH-induced reversal of ionic diode polarity in 300nm thin membranes based on a polymer of intrinsic microporosity

Author

Rong, Yuanyang, primary, Song, Qilei, additional, Mathwig, Klaus, additional, Madrid, Elena, additional, He, Daping, additional, Niemann, Ralf G., additional, Cameron, Petra J., additional, Dale, Sara E.C., additional, Bending, Simon, additional, Carta, Mariolino, additional, Malpass-Evans, Richard, additional, McKeown, Neil B., additional, and Marken, Frank, additional

Published
2016
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62. Bisecting Microfluidic Channels with Metallic Nanowires Fabricated by Nanoskiving

Author

Kalkman, Gerard A., primary, Zhang, Yanxi, additional, Monachino, Enrico, additional, Mathwig, Klaus, additional, Kamminga, Machteld E., additional, Pourhossein, Parisa, additional, Oomen, Pieter E., additional, Stratmann, Sarah A., additional, Zhao, Zhiyuan, additional, van Oijen, Antoine M., additional, Verpoorte, Elisabeth, additional, and Chiechi, Ryan C., additional

Published
2016
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68. Potential-Controlled Adsorption, Separation, and Detection of Redox Species in Nanofluidic Devices.

Author

Jin Cui, Mathwig, Klaus, Mampallil, Dileep, and Lemay, Serge G.

Subjects
*OXIDATION-reduction reaction, *NANOFLUIDIC devices, *ADSORPTION (Chemistry), *SEPARATION (Technology), *ELECTROCHEMISTRY, *ELECTRODES
Abstract

Nanoscale channels and electrodes for electrochemical measurements exhibit extreme surface-to-volume ratios and a correspondingly high sensitivity to even weak degrees of surface interactions. Here, we exploit the potentialdependent reversible adsorption of outer-sphere redox species to modulate in space and time their concentration in a nanochannel under advective flow conditions. Induced concentration variations propagate downstream at a speciesdependent velocity. This allows one to amperometrically distinguish between attomole amounts of species based on their time-of-flight. On-demand concentration pulse generation, separation, and detection are all integrated in a miniaturized platform. [ABSTRACT FROM AUTHOR]

Published
2018
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69. Ionic Transport in Microhole Fluidic Diodes Based on Asymmetric Ionomer Film Deposits.

Author

Mathwig, Klaus, Aaronson, Barak D. B., and Marken, Frank

Subjects
IONOMERS, IONOMER clusters, THIN films, BIOSENSORS, FINITE element method
Abstract

Abstract: Microhole fluidic ionic diodes based on asymmetric deposits of charged ionomer membranes (e. g. Nafion or polymers of intrinsic microporosity) on microhole supports yield high rectification ratios for ionic transport. They are fabricated without the need for complex micro‐ or nanostructuring, and show potential for future applications in desalination and biosensing. Here, we propose an explanation for the functional principle for this type of materials‐based ionic diode. A predictive computational model for ionic diode switching is based on finite element analysis. It is employed to determine the influence of diode geometry as well as type and concentration of aqueous electrolyte on the rectification behavior. [ABSTRACT FROM AUTHOR]

Published
2018
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70. Response time of electrochemical nanofluidic sensors

Author

Kang, Shuo, Mathwig, Klaus, Lemay, Serge Joseph Guy, and Faculty of Science and Technology

Subjects
METIS-291168, IR-84827
Abstract

Nanofluidic thin-layer cells count among the most sensitive electrochemical sensors built to date. Here we study both experimentally and theoretically the factors that limit the response time of these sensors. We find that the key limiting factor is reversible adsorption of the analyte molecules to the surfaces of the nanofluidic system, a direct consequence of its high surface-to-volume ratio. Our results suggest several means of improving the response time of the sensor, including optimizing the device geometry and tuning the electrode biasing scheme so as to minimize adsorption.

Published
2012

94. Microfluidic Digestive Systems for Drug Analysis

Author

Pim de Haan, Verpoorte, Elisabeth, Mathwig, Klaus, and Pharmaceutical Analysis

Subjects
Chemistry, Microfluidics, Nanotechnology, Drug analysis
Abstract

As most medicines are given orally, it is important to study what happens to new drugs upon ingestion. A better, more representative and more efficient model of the human gastrointestinal (GI) tract is required for these studies than used today. This thesis describes novel methods to test the behavior of drugs in the human GI tract based on continuously flowing microsystems. In order to reach the desired site of action, drug molecules must first survive the harsh conditions in the GI tract. Samples containing drugs or foods were exposed to artificial versions of digestive juices in micromixers to study the effects of digestion on the samples. The digested samples then reached a gut-on-a-chip – a miniaturized model of the human intestinal barrier – to study the absorption of drugs across a layer of living intestinal cells into the body compartment. This uptake process was studied using state-of-the-art analytical-chemical techniques such as mass spectrometry. Two different model drugs were studied in this system, with one drug clearly broken down by the preceding digestion. The second part of this thesis describes different novel methods and equipment for use in such gut-on-a-chip systems, including a control system to deliver liquids to organs-on-chips for longer experiments (days), new microfabrication strategies to produce very thin, porous membranes to serve as support for the gut-on-a-chip barriers, and 3D-printed components for use in microfluidic digestive systems. It is envisioned that the work described in this thesis may contribute to faster and more efficient studies of novel drugs and foods.

Published
2021
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95. Probing DNA - Transcription Factor Interactions Using Single-Molecule Fluorescence Detection in Nanofluidic Devices.

Author

Fontana M, Ivanovaitė Š, Lindhoud S, van der Wijk E, Mathwig K, Berg WVD, Weijers D, and Hohlbein J

Subjects
DNA chemistry, DNA Probes, Nanotechnology, Oligonucleotides, Fluorescence Resonance Energy Transfer, Transcription Factors
Abstract

Single-molecule fluorescence detection offers powerful ways to study biomolecules and their complex interactions. Here, nanofluidic devices and camera-based, single-molecule Förster resonance energy transfer (smFRET) detection are combined to study the interactions between plant transcription factors of the auxin response factor (ARF) family and DNA oligonucleotides that contain target DNA response elements. In particular, it is shown that the binding of the unlabeled ARF DNA binding domain (ARF-DBD) to donor and acceptor labeled DNA oligonucleotides can be detected by changes in the FRET efficiency and changes in the diffusion coefficient of the DNA. In addition, this data on fluorescently labeled ARF-DBDs suggest that, at nanomolar concentrations, ARF-DBDs are exclusively present as monomers. In general, the fluidic framework of freely diffusing molecules minimizes potential surface-induced artifacts, enables high-throughput measurements, and proved to be instrumental in shedding more light on the interactions between ARF-DBDs monomers and between ARF-DBDs and their DNA response element., (© 2021 The Authors. Advanced Biology published by Wiley-VCH GmbH.)

Published
2022
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96. High-throughput, non-equilibrium studies of single biomolecules using glass-made nanofluidic devices.

Author

Fontana M, Fijen C, Lemay SG, Mathwig K, and Hohlbein J

Subjects
DNA chemistry, Equipment Design, Glass, High-Throughput Screening Assays instrumentation, Immobilized Nucleic Acids chemistry, Microscopy, Fluorescence, Molecular Probes chemistry, DNA analysis, Lab-On-A-Chip Devices, Nanotechnology instrumentation, Single Molecule Imaging instrumentation
Abstract

Single-molecule detection schemes offer powerful means to overcome static and dynamic heterogeneity inherent to complex samples. However, probing biomolecular interactions and reactions with high throughput and time resolution remains challenging, often requiring surface-immobilized entities. Here, we introduce glass-made nanofluidic devices for the high-throughput detection of freely-diffusing single biomolecules by camera-based fluorescence microscopy. Nanochannels of 200 nm height and a width of several micrometers confine the movement of biomolecules. Using pressure-driven flow through an array of parallel nanochannels and by tracking the movement of fluorescently labelled DNA oligonucleotides, we observe conformational changes with high throughput. In a device geometry featuring a T-shaped junction of nanochannels, we drive steady-state non-equilibrium conditions by continuously mixing reactants and triggering chemical reactions. We use the device to probe the conformational equilibrium of a DNA hairpin as well as to continuously observe DNA synthesis in real time. Our platform offers a straightforward and robust method for studying reaction kinetics at the single-molecule level.

Published
2018
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