Alexandra Anne Labiba Kämpfer-Homsy

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In this paper we present two compact, quantum cascade laser absorption spectroscopy based, sensors developed for trace substance detection in gases and liquids. The gas sensor, in its most integrated version, represents the first system combining a quantum cascade laser and a quantum cascade detector. Furthermore, it uses a toroidal mirror cell with a volume of only 40 cm(3) for a path length of up to 4 m. The analytical performance is assessed by the measurements of isotope ratios of CO2 at ambient abundan

The efficiency of on-chip microfluidic liquid-liquid extraction was improved by two orders of magnitude by spraying one liquid in another compared to the state-of-the-H-filters. We are developing a portable, integrated optical microsystem in the mid-infrared range to detect cocaine in human saliva. To ensure a good signal-to-noise ratio, the analyte needs to be transferred to an IR-transparent organic solvent by liquid-liquid extraction for subsequent on-chip analysis by IR-spectroscopy. In microfluidics, l

In clinical diagnostics, the fluidic part for sample-preparation should not absorb any of the substances of interest. In this study, the absorption of 4 different interleukins was investigated in a newly developed microfluidic blood filtration element (BFE). The BFE is capable of extracting 8-15 μL volume of plasma from 100 μL of whole blood in 7 minutes. Whole blood from 4 separate human subjects was tested. The recovery from our BFE was lower than 100%, but, as it was reproducible (except for TNF-α), enab

Different methods to adjust the wetting behavior of surfaces of the UV-curable adhesive NOA81 were investigated and quantitatively characterized by dynamic contact angle measurements with an optical goniometer. A new method to make NOA81 surfaces hydrophobic by mixing an additive in the uncured polymer was presented. The effect was confirmed by surface roughness studies using atomic force microscopy and X-ray photoelectron spectroscopy measurements. The chemical resistance of NOA81 microfluidic channels was

We present a portable microsystem to quantitatively detect cocaine in human saliva. The chip combines a simple microfluidic method for multiphase liquid-liquid extraction to transfer cocaine from IR-light absorbing saliva to an IRtransparent solvent with t ...

An integrated chip for DNA hybridization detection was realized in a standard CMOS process: it hosts 80 biosensors subdivided in 2 channels, as well as D/A and A/D converters for electrical stimulation and readout. A microfluidic system, bonded on the surface of the chip, provides access to the sensing areas for test solutions and reagents. A simple, low-cost technique for the realization of a biocompatible interface on the aluminum sensing area was developed; it allows the immobilization of single-stranded

Based on a mid-infrared waveguide fabricated from Germanium on Silicon substrates, we present a concept of chemical sensors in aqueous solutions. The sensing scheme is utilizing the evanescent wave in a single-mode waveguide, and the absorption spectrum of chemicals dissolved in liquids. The waveguide is coupled to a singlemode mid-infrared quantum cascade laser [1], and an infrared detector. The wavelength of 5.81 microns is chosen to assure the specifity and sensitivity of the pilot application [2] for th

Clinical point of care testing often needs plasma instead of whole blood. As centrifugation is labor intensive and not always accessible, filtration is a more appropriate separation technique. The complexity of whole blood is such that there is still no commercially available filtration system capable of separating small sample volumes (10-100 mu l) at the point of care. The microfluidics research in blood filtration is very active but to date nobody has validated a low cost device that simultaneously filtr

In recent years, the Lattice Boltzmann Method (LBM) has been demonstrated as an interesting alternative for the simulation of complex fluid flows. Unlike finite elements models (FEM) based on a discretization of macroscopic continuum equations, the LBM is derived from microscopic models and mesoscopic kinetic equations [1]. As an increasing number of studies use acoustic standing waves for microfluidics applications [2], the LBM constitutes an efficient alternative to simulate complex interactions between f

We present a portable microsystem to quantitatively detect cocaine in human saliva. In this system, we combine a microfluidic-based multiphase liquid-liquid extraction method to transfer cocaine continuously from IR-light-absorbing saliva to an IR-transparent solvent (tetrachloroethylene) with waveguide IR spectroscopy (QC-laser, waveguide, detector) to detect the cocaine on-chip. For the fabrication of the low-cost polymer microfluidic chips a simple rapid prototyping technique based on Scotch-tape masters

The UV-curable adhesive NOA81 (Norland Optical Adhesive) is a promising liquid photopolymer for low-cost microfluidic chip production. Different fabrication methods for NOA81 are suggested [1,2]. However, optical characterization for fluorescent based detection systems is missing. We present a comparison of fluorescent emissionspectra of various NOA types as well as the time evolution of the spectra of the most promising one - NOA81. We report on a simple rapid prototyping technique to produce chips for flu

This paper describes the fabrication technique for the realization a microfluidic flow cell to be integrated on a CMOS biosensor for DNA hybridization detection. The main element of the microfluidic system is made in polydimethylsiloxane (PDMS) elastomer and takes up an area of 5 mm(2). PDMS is cast against a silicon master patterned by Deep Reactive Ion Etching (DRIE) and then bonded on the chip by means of oxygen plasma activation. The micro channels patterned in the flow cell are connected with capillary

A germanium strip waveguide on a silicon substrate is integrated with a microfluidic chip to detect cocaine in tetrachloroethylene solutions. In the evanescent field of the waveguide, cocaine absorbs the light at 5.8μm, which is emitted from a quantum cascade laser. The lowest measured concentration is 100μg/ml.

In this contribution we present our work on filtration of plasma from whole blood in a polymer-based microfluidic system. The absorption of pathogens was found to be low; therefore our system is valid for clinical trials. The blood filtration element is capable of extracting 8–15μL volume of plasma from 100μL of whole blood in 7 minutes.

Standalone integrated microfuidic systems require pumping elements. Electro-osmosis (EO) is an e"ective method of actuating liquids [1,2]. ACEO exploits much lower potentials and, by using alternating fields, overcomes the issues of electrolysis and gas generation

A germanium (Ge) strip waveguide on a silicon (Si) substrate is integrated with a microfluidic chip to detect cocaine in tetrachloroethylene (PCE) solutions. In the evanescent field of the waveguide, cocaine absorbs the light near 5.8 mm, which is emitted from a quantum cascade laser. This device is ideal for (bio-)chemical sensing applications.

Many popular micropumps implement moving parts that presents serious drawbacks. This is one of the reasons for the growing interest in valveless micropumps. Pumps exploiting AC electric fields are investigated here. Theoretical results are recalled and the behaviour of fabricated glass and PDMS prototypes is presented and compared to simulations. Recirculation of liquid in the pumping channel is explained by geometrical reasons.

The optical adhesive NOA81 (Norland Products Inc.) is a promising UV-curable material for low-cost microfluidic applications. We demonstrated that its surface energy can be adjusted by different surface treatments or by mixing an additive in the uncured bulk polymer, which is a serious asset to the development of microfluidic systems. The surfaces were characterized by dynamic contact angle measurements and the chemical resistance of NOA81 microchannels was tested by flowing organic solvents therein. The co

This paper reports on the fabrication and experimental characterisation of improved design AC eletroosmotic micropumps. Since the first study and analysis of AC electroosmosis by Ramos et al. [1], many devices have been fabricated and tested [2]. The basic planar electrode design was improved and increased pumping velocities were measured. Among the proposed improvements, 3D electrode design seems very promising [3,4]. Nevertheless, 3D electrode structures occupy a large portion of the channel cross section

A Si/Ge based, single mode, mid-infrared optical waveguide, is used as an evanescent sensor in liquid matrix. The selectivity is achieved by the use of quantum cascade lasers (QCLs) tuned to the maximum absorption of a given analyte. The cocaine detection ...

Alexandra Anne Labiba Kämpfer-Homsy

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Mid-infrared spectroscopy for gases and liquids based on quantum cascade technologies

Improved method for liquid-liquid extraction on low-cost polymer chips

Study of interleukin absorption in a blood filtration element for plasma separation

Norland optical adhesive (NOA81) microchannels with adjustable wetting behavior and high chemical resistance against a range of mid-infrared-transparent organic solvents

Droplet-based Liquid-Liquid Extraction and On-Chip IR-Waveguide-Spectroscopy Detection of Cocaine in Human Saliva

Label-free, direct DNA detection by means of a standard CMOS electronic chip

Mid-infrared Waveguide Evanescent Field Chemical Sensor for Liquids

Development and validation of a low cost blood filtration element separating plasma from undiluted whole blood

On the Simulation of Acoustic Standing Waves for Microfluidic Applications with the Lattice Boltzmann Method

Microfluidic Droplet-Based Liquid–Liquid Extraction and On-Chip IR Spectroscopy Detection of Cocaine in Human Saliva

Microfluidic devices made of UV-curable glue (NOA81) for fluorescence detection based applications

Integration of a microfluidic flow cell on a CMOS biosensor for DNA detection

Mid infrared waveguide spectroscopy for cocaine detection in liquid environments

Clinical Validation of a Blood Filtration Element for Plasma Separation at the Point of Care

Inkjet Printed Conductive Polymer Electrodes for AC Electroosmosis

Cocaine detection by a mid-infrared waveguide integrated with a microfluidic chip

Flow recirculation when pumping liquids with AC electric fields: experiments and simulations

Norland optical adhesive (NOA81) microchannels with adjustable surface properties and high chemical resistance against IR-transparent organic solvents

Improved Two-Side AC Electroosmotic Micropump

Single Mode Mid-infrared Waveguide for Evanescent Sensor Scheme in Liquids