Jan Reboun

Electrophoresis deposition of metal nanoparticles with reverse micelles onto InP

Abstract Nanolayers were deposited onto surfaces of n-type InP single crystal wafers by electrophoresis from reverse micelle colloid solutions containing palladium nanoparticles. Two types of nanolayers were deposited, by applying a positive potential or a negative potential on the InP wafer. Further, wafers with nanolayers were annealed in high vacuum at 400 °C. The nanolayers were studied using capacitance–voltage characteristics on a mercury probe, by atomic force microscopy and by secondary-ion mass spectroscopy. Two types of Schottky-like diodes were prepared on wafers with the two types of nanolayers and studied by current–voltage characteristics. The diodes with nanolayers deposited by applying the positive potential, which contained Pd nanolayers, showed characteristics with better rectifying properties than the other type of diodes. Correlations among measured characterizations were found.

Comparison of the surface properties of power electronic substrates

This paper deals with thick film copper technology (TFC) and its comparison with other power electronic substrates such as a printed silver or direct bonded copper (DBC) on alumina substrates. The research activities were concentrated on surface properties of power substrates and its solderability. The solderability of thick film copper is comparable with other power electronic substrates such as DBC, but it is necessary to ensure proper firing condition or remove oxides from the surface after firing and use a proper flux. The main advantages of thick film copper in comparison with common power electronic substrates are a high resolution of conductive pattern, higher reliability at thermal cycling and a possibility to create a different local thickness of copper layer on substrate. Maximal thickness of copper layer can reach 300 μm.

Organic based sensors: Novel screen printing technique for sensing layers deposition

This paper presents a research focused on development of low-cost manufacturing process which enables fabrication of accurate organic humidity sensors, where only screen printing is used for all layers deposition. It means that not only the interdigital structures with 50 μm line and space, but also phatolocynine sensing film and protective polymer layer are screen printed. The interdigital structures are printed by advanced screen printing in order to replace complex an expensive vacuum processes. In the frame of this research a novel screen printing technique for deposition of low viscose organic sensing film was also developed, where non-standard precise stainless steel Beta mesh was used for screens.

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 materials for humidity sensors

This paper deals with research and development of organic humidity sensors. These sensors are based on gold interdigital electrodes placed on the glass substrate covered by the thin layer of organic sensitive material. The sulfonated aluminium phtalocyanine was used as the prospective sensitive material. The advantage of organic sensitive materials instead of inorganic is the easier deposition of thin films, their higher modifiability and lower cost. Electrical parameters of organic sensors were measured at variable relative humidity and temperature. The influence of aging and frequency behaviour was also measured in detail.

Smart textile-based protective system for firefighters

This paper presents a research focused on a smart textile-based protective system which is intended to bring more safety to firefighters facing hazardous conditions. The system is fully integrated into a firefighter protective suit and it is able to monitor heart rate (HR), to detect movements of a firefighter, to detect toxic and combustible gases in the environment and to measure temperature (T) and relative humidity (RH) inside and outside of the suit. The protective system consists of developed integrated sensor modules, e-textile wiring harnesses, body control unit (BCU), central processing unit (CPU), body area network (BAN) and wide area network (WAN). The measured data are wirelessly transmitted over a wide area network with automatic routing algorithm to the central processing unit, which is checked by a firefighter operation chief, who is kept informed about an actual state of individual fire fighters. In case that some monitored parameter oversteps pre-set threshold values the BCU will automatically inform a fire fighter by means of acoustic alarm about oncoming risk.

Perspective methods of creating conductive paths by Aerosol Jet Printing technology

This paper presents a research focused on four-wire resistivity measurement of the selected materials printed by Aerosol Jet Printing system (AJP) with different process parameters. The aerosol jet printing technology is an additive deposition technique which is based on the idea of the formation the aerosol mist from the printed ink and its transportation on the substrate by gas flow. The aerosol formation - the atomization process can be made by two different ways. One way is the pneumatic atomizer which smashes the ink on the wall of the jar and so creates the aerosol. The inks of viscosity from 1 to 1000 mPa·s can be used. The second way is the ultrasonic atomizer which creates the aerosol by smashing the ink by ultrasonic waves. In ultrasonic one, the viscosity of the ink should be in the range from 1 to 5 mPa·s. Three different conductive inks based on nanoparticles were printed to the form of the test pattern. Printing parameters were optimized in order to achieve highest conductivity of printed line. The impedance measurement and used inks are described in this paper. The main application of such aerosol jet printed materials could as follows: organic electro-chemical transistors (OECT), gas sensors, smart ID cards or RFID antennas.

Textile based temperature and humidity sensor elements for healthcare applications

This paper presents a research focused on embroidered temperature and humidity sensor elements for smart textile applications in health and medical care. Smart textile products face desirable textile properties for health care use include durability, “launderability” (washing resistance), flexibility and non-toxicity and the comfort aspect of clothing is also very important. For these reasons, the presented research was concentrated on the development of sensor elements based on specially prepared conductive yarns which are integrated into textile fabric with the familiar textile technique - embroidery and connected to control unit through snap fasteners. All the sensor element manufacturing steps are fully compatible with textile processing techniques. The preliminary investigation into the design, manufacturing and testing of the textile based temperature and humidity sensor elements are described in the paper.

Thick printed copper conductors on alumina substrates

This paper deals with a method for design and manufacturing of power electronic substrates. Thick conductive patterns are made by the additive deposition technique using thick copper conductor paste. Substrates with excellent thermal and electrical conductivity, high resistance to thermal cycling stress, high resolution of printed patterns and good mechanical properties are created by this manufacturing process. Gas-tight retort, we used for this specific substrate manufacturing process, is also described in this paper. Mechanical properties of substrates such as adhesion, as well as thermal and electrical properties, were tested in detail.

Screen printed antennas on textile substrate

This article deals with screen printed antennas on textile substrate that are used for data transmission between intelligent fireman suits. Today the smart textiles are developed in the whole world and research works are focused on integration of electronic devices and systems into textiles. There are different technologies how to do it. Screen printed electronic devices on textile substrates are one of the perspective possibilities how to create electronic devices on textiles. Screen printing technology uses conductive pastes for functional pattern creation. This technology reduces significantly the manufacturing cost, is simple to use and is more and more used in electronics.