Presenter

Mr. Vladimir Matvejev - ETRO [Email]

Abstract

Electromagnetic waves at Terahertz frequencies (300-3000GHz) allow to probe weak inter- and intra-molecular interactions of biomolecules in physiological buffer, therefore facilitating a label-free, immobilization-free, real-time and non-invasive biosensor approach. The fundamental limitations for the development of applications are: a) strong water absorption and insufficient performance of active devices cause low sensitivity due to a short interaction path length, b) long wavelength and insufficient confinement lead to large sample volumes.
This PhD thesis describes the operation, fabrication and performance evaluation of an integrated sensor’s passive part, the purpose of which is to increase the measured signal response to aqueous sample dielectric permittivity changes caused by e.g. bio-molecular processes. To this end a broad range of THz specific R&D facilities are required, including electromagnetic modeling tools, micro-fabrication processes and measurement instrumentation.
A substrate integrated waveguide with non-conventional cross-section is used as the basis for the structure its relative propagation modes and parameters are discussed. The sensor structure substantially increases the interaction efficiency of the electromagnetic wave with the aqueous sample and allows to reduce drastically the sample volume. A sensor configuration featuring an exceptionally high Q-factor notch for water filled structures results in an impressive sensitivity. The performance of the sensor is evaluated with a set of biologically relevant particles: alcohols, protein, DNA, cells. At a frequency f=300GHz and with sample volume V=4nL the achieved low detection limit and high sensitivity: e.g. for DNA is of the order 10 mg/L (or 0.3nmol/L) and 0.04 dB(mg/L)^-1, respectively. Proof of principles in biomolecule concentration, conformation, binding and cell physiology measurements will be discussed. We highlight the importance of dielectric permittivity changes due the presence and changes of hydration water in aqueous biomolecule solutions, which is dependent on the biomolecules´ surface and volume properties. A methodology is developed to quantify hydration water in terms of size and absorption, which is demonstrated with aqueous alcohol solutions.
The novel THz biosensor of this work has a high potential as an emerging biophysical analytical tool in pharmaceutical, clinical and medical applications.

Short CV

Master of Science, Furtwangen University, Germany, 2009