Vojtech Svatos

Sensing properties of multiwalled carbon nanotubes grown in MW plasma torch: electronic and electrochemical behavior, gas sensing, field emission, IR absorption.

Vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with an average diameter below 80 nm and a thickness of the uniform VA-MWCNT layer of about 16 μm were grown in microwave plasma torch and tested for selected functional properties. IR absorption important for a construction of bolometers was studied by Fourier transform infrared spectroscopy. Basic electrochemical characterization was performed by cyclic voltammetry. Comparing the obtained results with the standard or MWCNT‐modified screen-printed electrodes, the prepared VA-MWCNT electrodes indicated their high potential for the construction of electrochemical sensors. Resistive CNT gas sensor revealed a good sensitivity to ammonia taking into account room temperature operation. Field emission detected from CNTs was suitable for the pressure sensing application based on the measurement of emission current in the diode structure with bending diaphragm. The advantages of microwave plasma torch growth of CNTs, i.e., fast processing and versatility of the process, can be therefore fully exploited for the integration of surface-bound grown CNTs into various sensing structures.

Design of the charge push-through electronics for fully implantable artificial cochlea

The artificial cochlear implant is the only way how to get lost hearing back in some cases. Existing artificial cochlear devices use two separated parts for this purpose: a signal processing unit with transmitter and an implantable receiver with electrodes. This approach is applicable but not fully implantable. A new complex approach to design of a fully implantable artificial cochlea is described in this article. The proposed artificial cochlea consists of many subcircuits which have to be designed in close context to reach optimal performance and the lowest power consumption. Power consumption should be decreased to a value which allows using cochlear implant as a zero-powered system. A combination of micro-mechanized diaphragm filter bank, possible energy harvesting power source and especially ultra-low power processing electronics is presented in this article. A unique technique for nerve stimulatory output signal generation is discussed. This new technique named charge push-through electronics should use the major part of energy generated by energy harvesting subcircuit for output useful signal generation with minimal undesirable current. Mechanical parts of the subcircuits were simulated as complex electro-mechanical simulation models in ANSYS, CoventorWare, Matlab and SPICE environment. First, the real energy harvesting power source (human motion and temperature) behavior was measured. The model of this behavior was created in simulation environment and then the whole electronics simulation model for energy harvesting circuits was estimated. Next, signal processing circuits powered from energy harvesting power source were designed and simulated. The new signal processing circuits were simulated in relation to the results of complex electro mechanical diaphragm and SPICE energy harvesting power source simulation.

Design of an Artificial Microelectromechanical Cochlea

The paper presents the first results of research on an artificial cochlea based on a mechanical filter bank that could be produced by MEMS (Micro Electro Mechanical Systems) technologies and power supplied by energy harvesting systems. First, the basic configuration of the artificial cochlea proposed by our team is described. Then, the configuration of mechanoelectrical transducers (polycrystalline diffused piezoresistors) displayed in the first experiment is offered. Finally, the eigenfrequencies of resonant membranes calculated employing finite element systems Ansys and CoventorWare are introduced.

Biosensing Surfaces Based on Quantum Dots Array

The fabrication of self-ordered semiconductor (TiO2) and noble metal (Au) QDs arrays was successfully achieved by advanced nonlithographic template based method, namely using nanoporous alumina template. The emphasis was placed on the successful preparation of QDs arrays with the desired size, homogeneous distribution and optical (especially fluorescence) properties. Titania and gold QDs characterization by SEM, EDX and fluorescence spectroscopy was performed in order to verify their surface topography, chemical composition and emission properties in UV/VIS range of spectra, respectively. The surface biofunctionalization of QDs was realized via simple physical adsorption of glutathione tripeptide, which makes these arrays suitable for potential biosensing application, mainly in optical and electrochemical detection of biomolecules in vitro.

Photo-Reflective Layer on Low Temperature Co-Fired Ceramic for Optical Applications

The article deals with photo-reflective layer on Low Temperature Co-fired Ceramic substrate deposition. Measurement of diffusion and specular reflectance and roughness of layer is included. Fabrication process and its optimization is also mentioned. For measurement of deposited layer optical properties, spectrometric method in spherical chamber was used. Further, profile of layers surface was measured by profilometer to acquire dependence between roughness and reflectivity. The main aim of work is to map the possibility of creation of photo-reflective layer on electrical, chemical and thermal resistant substrate in simple way.