Tomas Dzugan

Sensorial characteristics of conductive polymers

This paper deals with the investigation of intrinsic conductive polymer PEDOT-PSS and development of vapour sensors. These sensors are based on the specific vapours influence on the electrical parameters. The designed sensors consist of glazed ceramic substrate with gold interdigital electrodes covered by a thin layer of conductive polymer. The insulation gap between electrodes was investigated in the range of 50 – 200 µm in order to achieve the maximal sensitivity. Temperature and humidity dependences of PEDOT-PSS layers were measured in the climatic chamber, influence of particular vapours on electrical parameters were measured in the special gas chamber. Except for temperature, humidity and vapour sensitivity, long term stability was also studied.

Organic humidity sensors - improvement of climatic resistance

This paper deals with research and development of humidity sensors based on organic sensitive materials. Organic sensors consist of the substrate with the electrode system covered by the thin sensitive organic layer. The base substrate consists of 99 % alumina. Golden electrodes have the interdigital form with the isolation gap 25 µm wide and finger 25 µm wide. Organic material is applied on the substrate by the spin coating. The main work was focused on the enviromental stabilization of organic sensor layers.

Influence of nano and microparticles on the development of electrical trees

This paper deals with the effect of inorganic micro/nanofillers on electrical tree growth in high voltage insulation during application of AC voltage of 20 kV, 50 Hz. Pure epoxy samples were subject of experiment as well as epoxy micro/nanocomposites with hydrophobic nanosilica or hydrophilic microsilica. The times to breakdown were evaluated and compared. A transparent resin was used allowing observation of electrical tree grow with the help of an optical microscopes. Also the X-ray computed tomography was used for the 3D visualization of electrical trees in evaluated samples. The results show that the time required for the tree development and breakdown increases when a nanofiller or a microfiller is used. The tree growth optical patterns are different for pure epoxy, epoxy microcomposites and epoxy nanocomposites. The possible reasons why and how nanoparticles prolongs the time to breakdowns is discussed.

Stabilization of organic materials for sensors

This paper deals with research and development of organic humidity sensors. These sensors are based on organic sensitive layer which is applied on the substrate with interdigital electrodes. The main work is focused on the stabilization of organic sensor layers. The stabilisation of mechanical and electrical parameters is based on passive polymer matrix where the active organic sensitive material is fixed. The sensor sensitivity, impedance-humidity characteristics and long term stability of electrical parameters were measured and discussed in detail.

The usage of nonwoven nanofibers for improving properties of electrical insulation

The nonwovens and nanofibers as a new material for possible improving properties of electrical insulation are introduced in this paper. Nanofibers were used to modify a commonly used two-component like mica-based high voltage electrical insulating material. The tested material in the form of resin-rich sheets was modified using a various number of layers (1, 2 and 3) of the nanofibers made from Polyamide 6 (PA6) in the various surface densities (1, 2 and 3 g·m-2). Specimens were manufactured at increased temperature and pressure. The volume resistivity, voltage dependence of dissipation factor and mechanical properties were tested. The structure of the nanofibers was examined by scanning electron microscopy (SEM), the manufactured composites were analyzed under optical microscopy. Obtained results showed that composites with layers of nonwoven nanofibers are characterized by lower values of dissipation factor at electric field intensity greater than 5 kV/mm when the partial discharge activity starts to occur. Mechanical tests showed that while the Youngs modulus of the modified composites notably increased (of about 27 - 43.5 %), flexural strength stayed on the same values as unmodified composites.

Design of a singlet oxygen generator based on LED emitters

This article deals with the research of singlet oxygen generation using phthalocyanine photosensitizer. Singlet oxygen is extraordinary reactive and can be used in many applications such as photodynamic therapy, disinfection or chemical synthesis. For singlet oxygen generation, the photosensitized method in a new developed generator based on LED emitters was used. The amount of singlet oxygen generated by LED emitters was compared with laser excitation. The principle of measurement, design of a singlet oxygen generator and control unit are discussed in more detail.

Electrical characterization of PEDOT:PSS

The purpose of this paper is to summarize the results of electrical measurements carried out on different types of metal-semiconductor heterojunctions based on PEDOT:PSS in order to examine the possibilities of either ohmic contacts or rectifying Schottky junctions formation. The character of created junctions was evaluated according to their I–V characteristics. Unusual electrical behaviour was observed in the case of heterojunctions formed on gold, platinum and carbon with a region of negative differential resistance. The phenomenon supposed to be partly responsible for such nonlinearity is existence of thin barrier layer on the surface of dried PEDOT:PSS, through which charge carriers could pass by tunneling. However, deeper investigation will be necessary to enlighten all the circumstances leading to origin of this behaviour.

Electrical properties of PEDOT

This article deals with electric properties of metal-organic semiconductor junction. Different types of substrates were used for measurement of electrical parameters of poly(3,4-ethylenedioxythiophene) (PEDOT). On these substrates, the thick layer of PEDOT was created. Current-voltage characteristics were measured to find-out if Schottky barrier on the metal-emiconductor junction is created. Then frequency characteristics were measured to obtain an equivalent circuit of this system.

Comparative study of printed circuit board substrates used for thermal management of high power LEDs

The goal of this study is to compare thermal parameters of different substrates for high power light-emitting diodes (LEDs) with emphasis on the cost and size. The standard glass epoxy substrate (FR4) with thermal vias and insulated metallic substrate (IMS) were chosen as suitable samples for this study. Thermal simulation and thermal start-up were performed in order to evaluate the heat dissipation of high power LED.

Cross-sensitivity of humidity sensor layers based on organic materials

This article deals with the research of an impact of various gases and vapours on electrical parameters of phthalocyanine. Cross-sensitivity was researched in order to exclude a negative impact of organic vapours on humidity sensor. Thin layer of phthalocyanine was exposed to various vapours, and then responses of its electrical characteristics were measured. This suitable material for humidity sensors, was deposited from the liquid phase on a substrate with interdigital electrodes and than exposed to the effect of analytes. Subsequently, the impedance characteristic of this thin film layer was measured. The comparison of responses to various gases and vapours is discussed in more detail as well.