Home | Legals | Sitemap | KIT
Michael Rapp
Dr. Michael Rapp
Novel Detection Methods in Biological and Chemical Sensing

Phone: +49 721 608-23238
michael rappOqe0∂kit edu

Staff webpage


Novel Detection Methods in Biological and Chemical Sensing

Dr. Michael Rapp

The research activity involves miniaturized methods for the chemical and biological detection in analytical micro systems.


Biosensing based on Surface Acoustic Wave (SAW) Technology

This method resembles the approach of the more known technology of SAW based gas sensing, a topic which is covered by this group as well. For bioanalysis the SAW sensors are modified in such way that they allow operation in aqueous media and thus allow the use as biosensor. Binding events of analyte molecules on the sensor surface result in a change of the acoustic wave velocity. Since the sensor is the frequency determining element of an electric oscillator the change of SAW velocity result in a change of the resonance frequency.

SAW devices coated with biologically active capture molecules enable the selective detection of the corresponding biomolecules with a high sensitivity in aqueous media. The non-modified surface of the device consists of free crystal surface and of metal electrodes. In order to chemically homogenize the surface we use a special polymer coating (~100nm) precipitated by means of a chemical vapor deposition process. If higher but especially defined layer thicknesses are used in the range of a few µm additionally acoustic resonant effects can be generated in these polymer layers. This effect can amplify the bioanalytical signals from the sensors up to factor of 10. These so called “Love Wave“ sensors offer interesting future perspectives.


Fast and low cost chemical sensing for food analysis and the detection of hazardous industrial organic compounds (TIC)

Our actual main focus is on the characterization of fuels and with external partners on the analysis of coffee. For these applications our core technology is used: A self developed SAW based sensor arrays for the detection of gases or vapors. Each sensor in the array is coated differently with a gas interacting sensing film, mostly a special polymer. The result is a selective detection of the gas or gas mixtures even by using semi-selective sensitive coatings. With proper sampling techniques the sensitivity and selectivity of the related chemical sensor system can be significantly enhanced allowing the detection of very complex gas mixtures like food aroma or the detection of distinct hazardous gases down to a sensitivity level of a few parts per billion (ppb).


Bi-phase Liquid Micro Systems

Micro Systems using non-miscible liquids for different new applications. One is sensing and counting of particles in liquids using flow focusing in conjunction with a capacitive coupled contactless conductivity detection (C4D). This technique allows biochemical analysis without immobilization of receptive molecules. As consequence common problems in terms of repeatability or reproducibility is dramatically improved. Other projects involve new methods of referencing acoustic based biosensors allowing a significant better signal to noise ratio.