Ulrich J. Krull

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The marriage of microfluidics with detection technologies that rely on highly selective nucleic acid hybridization will provide improvements in bioanalytical methods for purposes such as detection of pathogens or mutations and drug screening. The capability to deliver samples in a controlled manner across a two-dimensional hybridization detection platform(More)
Surface plasmon microscopy is applied to monolayers of dimyristoylphosphatidylethanolamine, dipcast at high lateral pressure (35 mN/m) on a solid substrate. The vertical resolution of better than 1 nm and an in-plane resolution of-10 pm allow for the detection of two separate solid domains. Assuming a fixed value for the lipid refractive index, the tilt(More)
A CMOS tunable-wavelength multi-color photogate (CPG) sensor is presented. Sensing of a small set of well-separated wavelengths (e.g., > 50 nm apart) is achieved by tuning the spectral response of the device with a bias voltage. The CPG employs the polysilicon gate as an optical filter, which eliminates the need for an external color filter. A prototype has(More)
A spectral-multiplexed fluorescence contact imaging microsystem for DNA analysis is presented. The microsystem integrates a filterless CMOS Color PhotoGate (CPG) sensor that exploits the polysilicon gate as an optical filter, and therefore does not require an external color filter. The CPG is applied to fluorescence-based transduction in a spectrally(More)
Bioassays based on cellulose paper substrates are gaining increasing popularity for the development of field portable and low-cost diagnostic applications. Herein, we report a paper-based nucleic acid hybridization assay using immobilized upconversion nanoparticles (UCNPs) as donors in luminescence resonance energy transfer (LRET). UCNPs with intense green(More)
Semiconductor quantum dots (QDs) have served as the basis for signal development in a variety of biosensing technologies and in applications using bioprobes. The use of QDs as physical platforms to develop biosensors and bioprobes has attracted considerable interest. This is largely due to the unique optical properties of QDs that make them excellent(More)
Organic fluorophores and quantum dots are ubiquitous as contrast agents for bio-imaging and as labels in bioassays to enable the detection of biological targets and processes. Upconversion nanoparticles (UCNPs) offer a different set of opportunities as labels in bioassays and for bioimaging. UCNPs are excited at near-infrared (NIR) wavelengths where(More)
The use of quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET) offer several advantages for the development of multiplexed solid-phase QD-FRET nucleic acid hybridization assays. Designs for multiplexing have been demonstrated, but important challenges remain in the optimization of these systems. In this work, we identify several(More)
Multiplexed fluorescence-based assays are possible by immobilization of mixtures of different nucleic acid QD-bioprobes onto fused silica optical fibers, and onto glass surfaces of glass-PDMS microfluidic chips. Dynamic control of stringency by adjustment of the electrical potential to drive electroosmotic flow is advantageous. QD-bioprobes can be(More)
Issues of water quality are a global problem with potentially devastating results in communities if microbial levels are not monitored and controlled effectively.This is especially true with the potential threat of bioterrorist contamination of water supplies.This study presents a method for quantifying microbial water pathogens by 5' nuclease real-time(More)
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