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Ole Hansen

Publications and source records attributed to Ole Hansen.

7 recordsLinked to original sources
PubMed2006

Strained silicon as a new electro-optic material.

For decades, silicon has been the material of choice for mass fabrication of electronics. This is in contrast to photonics, where passive optical components in silicon have only recently been realized. The slow progress within silicon optoelectronics, where electronic and optical functionalities can be integrated into monolithic components based on the versatile silicon platform, is due to the limited active optical properties of silicon. Recently, however, a continuous-wave Raman silicon laser was demonstrated; if an effective modulator could also be realized in silicon, data processing and transmission could potentially be performed by all-silicon electronic and optical components. Here we have discovered that a significant linear electro-optic effect is induced in silicon by breaking the crystal symmetry. The symmetry is broken by depositing a straining layer on top of a silicon waveguide, and the induced nonlinear coefficient, chi(2) approximately 15 pm V(-1), makes it possible to realize a silicon electro-optic modulator. The strain-induced linear electro-optic effect may be used to remove a bottleneck in modern computers by replacing the electronic bus with a much faster optical alternative.

Journal Article↗
PubMed2006

Dielectrophoresis microsystem with integrated flow cytometers for on-line monitoring of sorting efficiency.

Dielectrophoresis (DEP) and flow cytometry are powerful technologies and widely applied in microfluidic systems for handling and measuring cells and particles. Here, we present a novel microchip with a DEP selective filter integrated with two microchip flow cytometers (FCs) for on-line monitoring of cell sorting processes. On the microchip, the DEP filter is integrated in a microfluidic channel network to sort yeast cells by positive DEP. The two FCs detection windows are set upstream and downstream of the DEP filter. When a cell passes through the detection windows, the light scattered by the cell is measured by integrated polymer optical elements (waveguide, lens, and fiber coupler). By comparing the cell counting rates measured by the two FCs, the collection efficiency of the DEP filter can be determined. The chips were used for quantitative determination of the effect of flow rate, applied voltage, conductivity of the sample, and frequency of the electric field on the sorting efficiency. A theoretical model for the capture efficiency was developed and a reasonable agreement with the experimental results observed. Viable and non-viable yeast cells showed different frequency dependencies and were sorted with high efficiency. At 2 MHz, more than 90% of the viable and less than 10% of the non-viable cells were captured on the DEP filter. The presented approach provides quantitative real-time data for sorting a large number of cells and will allow optimization of the conditions for, e.g., collecting cancer cells on a DEP filter while normal cells pass through the system. Furthermore, the microstructure is simple to fabricate and can easily be integrated with other microstructures for lab-on-a-chip applications.

Cell Separation↗
PubMed2006

Mechanical properties of organic nanofibers.

Intrinsic elastic and inelastic mechanical properties of individual, self-assembled, quasi-single-crystalline para-hexaphenylene nanofibers supported on substrates with different hydrophobicities are investigated as well as the interplay between the fibers and the underlying substrates. We find from atomic-force-microscopy-based rupture experiments a rupture shear stress of about 2 x 10(7) Pa for an individual fiber. Deflecting a nanofiber suspended across a gap results in a Young's modulus of 0.65 GPa. Translational motion of intact nanofibers across the surface is demonstrated for fibers on a silicon substrate with a low-adhesion coating, whereas such motion on a noncoated substrate is limited to very short (sub-micrometer) nanofiber pieces due to strong adhesive forces.

Adhesiveness↗
PubMed2005

Surface-directed capillary system; theory, experiments and applications.

We present a capillary flow system for liquid transport in microsystems. Our simple microfluidic system consists of two planar parallel surfaces, separated by spacers. One of the surfaces is entirely hydrophobic, the other mainly hydrophobic, but with hydrophilic pathways defined on it by photolithographic means. By controlling the wetting properties of the surfaces in this manner, the liquid can be confined to certain areas defined by the hydrophilic pathways. This technique eliminates the need for alignment of the two surfaces. Patterned plasma-polymerized hexafluoropropene constitutes the hydrophobic areas, whereas the untreated glass surface constitutes the hydrophilic pathways. We developed a theoretical model of the capillary flow and obtained analytical solutions which are in good agreement with the experimental results. The capillarity-driven microflow system was also used to pattern and immobilize biological material on planar substrates: well-defined 200 microm wide strips of human cells (HeLa) and fluorescence labelled proteins (fluorescein isothiocyanate-labelled bovine serum albumin, i.e., FITC-BSA) were fabricated using the capillary flow system presented here.

Adsorption↗
PubMed2004

Troponin must be measured before and after PCI to diagnose procedure-related myocardial injury.

OBJECTIVE: To evaluate troponin I >99th percentile of normal as a criterion for myocardial injury after percutaneous coronary intervention (PCI). DESIGN: Troponin I and creatine kinase monobasic (CK-MB) were measured in 327 patients before and after percutaneous transluminal coronary angioplasty (PTCA) with stent implantation. RESULTS: Troponin I was elevated before PCI in 100 of a total of 222 patients with acute coronary syndrome (ACS). In 91 of these 100 patients, troponin I was elevated also after PCI but actual increases in troponin I concentrations from before to after PCI were found in only 32 patients. The increase of troponin I correlated with post-procedural CK-MB whereas post-procedural troponin I levels did not correlate. In the 122 patients with ACS but normal/normalized troponin I before PCI and in 105 patients with stable coronary artery disease post-procedural troponin I appeared to be a reliable indicator of myocardial infarction (MI), however more sensitive than CK-MB. CONCLUSION: Troponin I after PCI is sensitive to pre-procedural concentrations. To avoid false positive MI diagnoses we thus suggest that troponin I should be measured before as well as after the procedures and only actual increases should be regarded as indicating procedure-related MI.

Aged↗