Holger Dirac's research while affiliated with Danfoss A/S and other places

Publications (7)

Article
Full-text available
The demand for continuous glucose monitoring systems is greater than ever. The microelectromechanical systems (MEMS) approach has the advantage of being relatively easy to upscale to a commercial level; the preferred MEMS technique would be to run several detectors at once and, through the improved statistics, get a both more accurate and more reli...
Article
The Berthelot reaction is a well-established colorimetric method for the determination of ammonia. It has been investigated with the particular aim of incorporating it into a simple, reliable analytical microfluidic sensing system. Absorbance measurements for the complex formed when this reaction is performed in microfluidic chips compare very well...
Conference Paper
We here report on the realisation of all liquid optical waveguides (ALOW). To our knowledge this is the first report in the literature on this topic. ALOWs are fluidic structures with waveguiding properties. They are realised in flow channels or tubes under laminar flow conditions, i.e. at moderate Reynolds numbers. The ALOW consists of an annular...
Article
Most μ-TAS developments are based on non-circular channel structures resulting from microelectronics processing technologies adapted to the fabrication of microfluidic networks. The dispersion due to pressure-driven flow in a microfluidic channel is shown to be highly dependent on channel cross-sectional geometry. For channels having rectangular cr...
Article
A prototype sensing-system for ammonia in water matrices has been designed and tested. The sensor is based on colorimetric detection (the indophenol blue reaction). It has been designed keeping in mind the features and performance parameters important for on-line sensing in industrial environments, such as effective sample pre-filtering, auto-calib...
Article
A novel approach for performing highly automated chemical analysis is presented. The method is based on well-controlled movement of paramagnetic particles in a convection-free liquid system. The magnetic particles are coated with reagent and are moved through the sample and reagents by magnetic forces. Less than 30 magnetic particles with a diamete...
Chapter
The method Magnetically Induced Chemical Analysis (MICA) has been developed for the automation of affinity assays. The method is based on manipulation of paramagnetic, spherical particles in stationary liquids. The particles are coated with affinity ligands, which allow both for selection and preconcentration of analyte. The interaction between the...

Citations

... Thereby, IR measurements [11] as well as electrochemical approaches like potentiometric electrodes [12] and conductometric [13], photoacoustic [14,15] photothermal [16], and amperometric methods [2] are worth mentioning. In analytical routine analysis, colorimetric methods based on Berthelot's [17,18] and Nessler's reaction [19] are well established. However, these methods either consume analyte, convert the analyte chemically into another species, or require expensive and bulky instrumentation. ...
... A system has been suggested for magnetic transportation towards miniaturization and automation, in which liquid movement is substituted with the help of magnetically induced movement of magnetic particles [114]. By arranging electromagnetic actuation in a four-phase scheme in microfluidic channel, magnetic particles have been transported above millimeter distances. ...
Reference: Talha TRAC-2016
... The lab-on-a-chip technology has made enormous progresses in the past decade. Beginning with microscopic sensors system for continuous blood glucose (24) and potassium (25) measurements, the new generation of microelectromechanical devices has the capability of measuring a vast array of biochemical analytes (26). Therefore, one can truthfully imagine the tremendous advantages of placing microscopic sensors for continuous monitoring of glucose and potassium into a blood tube. ...
... A portable CCD spectrophotometer (Ocean Optics S2000) and a tungsten halogen light source, connected via optical ®bers to the chip, perform absorbance detection of the solution passing through the built-in optical cell (described in more detail below). The channel structure of the micro¯uidic chips used during these experiments was designed as a compromise between low dispersion, low ¯ow resistance and short mixing time [24,25]. First generation devices were made of a silicon chip with etched channels sandwiched in between two Pyrex plates. ...
... Several structures are being explored for microfluidic optical sensing, including antiresonant reflection optical waveguides, interferometers, micro-chromatographs, surface plasmon resonance devices, scattering-enhanced Raman spectroscopy, and optofluidics [8][9][10][11][12][13]. A common difficulty for many microfluidic sensing methods is that the interaction length is small, making it difficult to detect low analyte concentrations. ...