Anders Wolff

Integrated polymer waveguides for absorbance detection in chemical analysis systems

A chemical analysis system for absorbance detection with integrated polymer waveguides is reported for the first time. The fabrication procedure relies on structuring of a single layer of the photoresist SU-8, so both the microfluidic channel network and the optical components, which include planar waveguides and fiber-to-waveguide coupler structures, are defined in the same processing step. This results in self-alignment of all components and enables a fabrication and packaging time of only one day. The fabrication scheme has recently been presented elsewhere for fluorescence excitation of beads. The emphasis of this paper is on the signal-to-noise ratio of the detection and its relation to the sensitivity. Two absorbance cells with an optical path length of 100 /spl mu/m and 1000 /spl mu/m were characterized and compared in terms of sensitivity, limit of detection and effective path length for measurements of the dye Bromothymol Blue. The influence of three different bonding procedures on the spectrally resolved propagation loss of the integrated waveguides between 500 nm and 900 nm was furthermore determined.

Microfabricated DNA amplification device monolithically integrated with advanced sample pre-treatment

We present the first example of a microfabricated PCR thermocycling chip integrated with advanced sample pre-treatment. The device consists of a SU-8 based PCR thermocycler chip monolithically integrated with dielectrophoretic (DEP) sample pre-treatment. This allows on chip purification of samples by removing inhibitors that would otherwise prevent PCR amplification. Integrated thin film heaters and a resistive temperature sensor control the PCR thermocycling. The sample pre-treatment system uses a combination of fluid flow and cell capturing by DEP to perform the sample treatment. The sample pre-treatment system was tested on a sample containing yeast cells and heparin that inhibits PCR. Only treated sample could be successfully amplified using PCR.

A High-Throughput SU-8Microfluidic Magnetic Bead Separator

We present a novel microfluidic magnetic bead separator based on SU-8 fabrication technique for high through-put applications. The experimental results show that magnetic beads can be captured at an efficiency of 91 % and 54 % at flow rates of 1 mL/min and 4 mL/min, respectively. Integration of soft magnetic elements in the chip leads to a slightly higher capturing efficiency and a more uniform distribution of captured beads over the separation chamber than the system without soft magnetic elements.

Studying different effects on the collection efficiency of a dielectrophoresis based selective filter in a microchip with integrated flow cytometers

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 positive DEP selective filter integrated with two micro flow cytometers for real-time monitoring of cell sorting processes. On the microchip, two flow cytometers are set upstream and downstream of the DEP filter. When a cell pass through the detection windows, the light scattered by the cell is measured by integrated polymer optical elements. The effects of flow rate, applied voltage, conductivity of the sample, and frequency of the electric field on the sorting efficiency of the chip were investigated. Using the chip, viable and non-viable yeast cells were sorted with high efficiency. At 2 MHz, more than 90 % of the viable and less than 10 % of the non-vial cells were captured on the DEP filter. Furthermore, the microstructure is simple to fabricate and can easily be integrated with other microstructures for lab-on-a-chip applications (164).