Jiri Navratil

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.

A comparison of the interdigital electrodes prepared by aerosol jet printing and lift-off technique

This paper presents a research focused on a comparison of the quality and electrical parameters of the interdigital electrodes prepared by aerosol jet printing (AJP) technique and conventional lift-off technique. The Interdigital electrodes (IDE) belong among the most commonly used periodic electrode structures for a wide variety of sensors and transducers. The IDE testing sample were designed with line/space widths of 25 μm/25 μm and active area of 4.32 × 4.55 mm. The advantages of the aerosol jet printing technique over conventional techniques consist in the fact that: a) it can produce high-resolution patterns (down to a feature size of 8 μm × 8 μm), b) it is maskless additive technique, c) it is compatible with flexible or even 3D substrates and d) it is compatible with a very large range of inks. In the frame of the research Clariant nanoparticle silver ink, Fraunhofer IKTS nanoparticle gold ink were aerosol jet printed on flexible PET and Kapton® polyimide substrates. Electrical and geometrical parameters were measured for each substrate deposited by AJP technique. The measured data of all testing samples deposited by AJP were compared to the measured ones of the samples realized by the lift-off technique on the alumina substrate.

A comparison of embroidered and screen-printed Ultra-Wideband antennas

This paper presents a research focused on a comparison of two antennas made on a textile substrate by two different technologies and optimized for Ultra-Wideband (UWB) communication. The first used technology was embroidering and the second one was screen-printing. The objective of the research was to achieve a flexible and washable antenna which would be possible to integrate into clothes without any side effects on its functionality.

Influence of flexible substrate roughness with aerosol jet printed pads on the mechanical shear strength of glued joints

This paper presents a research focused on Aerosol Jet printed pads adhesion improvement for electrically conductive adhesives (ECA) testing. The Aerosol Jet technology is able to use nanoparticle inks for deposition process. The adhesion of the ink to the substrate is crucial especially when you realize printing on flexible substrates. The paper will show a new method of adhesion improvement by plasma treatment and fine sandpaper grinding. The adhesion testing was realized by shear strength test of glued joints. Ten SMD chip resistors 1206 were mounted to the electrically conductive adhesive on aerosol jet printed pads for each sample. The advantages, disadvantages and full results of adhesion improvement method are discussed in the paper.

Aerosol Jet silver printed lines on subsequently bent glass substrates

This paper presents a research focused on Aerosol Jet printed lines on subsequently bent glass substrates. The thin glass rods were used as the glass substrates. Three different patterns were printed by silver nanoparticle ink on the thin rods and the ink was sintered. The thin rods were bent in a flame in different angles after the ink sintering. The resistivity was measured before and after the bending and also the microscopic observation was realized in order to discover which of the printed patterns is the best for bending.

Nanoparticle based ink printed chip interconnections

This paper presents a research focused on Aerosol Jet interconnecting of SMD components to flexible substrates. Flexible printed electronics is becoming important fast growing market segment. Contacting technologies of the electronic components are well known for traditional electronics such as soldering, welding, conductive adhesive bonding, however in the expansion of direct printing technologies the new possibilities have raised. Without using of conductive adhesives the Aerosol Jet technology can be used for contacting. The interconnections were realized by silver nanoparticle ink. Two possible options were examined — direct interconnecting and interconnecting with dielectric blob. Issues of the Aerosol Jet interconnecting, used materials and measured data are discussed in the paper.

Numerical and experimental analysis of electrostatic adhesion force generated by interdigital electrodes

Electrostatic adhesion force is studied and analysed with emphasis on design parameters of the interdigital electrodes, material properties of dielectric layers and its thickness. From these results two fabrication processes of the electroadhesive foils are studied to reach the highest possible performance. Experimental measurements are carried out to verify the results.

Connection technologies quality improving

This article introduces the possibility of using optimization methods FMEA and DOE to improve experimental research processes. The FMEA methodology was implemented in the pre - experimental phase of the experiment. Potential risks were established by FMEA methodology. From these risks were chosen by brainstorming such risks that have the biggest impact on the overall result of the experiment. These risks were tested during the experiment. After the execution of the experiment, the data were evaluated by DOE methodology. This methodology was used to verify whether the risks were selected and tested with truly significant impact to results of experiment.

Low-voltage electrochemical transistor based on ionic liquid-gated PEDOT:PSS with copper electrodes

One of viable routes to a broader employment of printed and flexible electronics resides in combination of novel functional printing techniques and existing industrial processes. We have investigated potential combination of industrial continuous foil metallization with screen printing to prepare low voltage electrochemical transistor. The transistor based on vacuum evaporated copper electrodes, screen printed channel from PEDOT:PSS and manually deposited ionic liquid exhibited low voltage operation with saturated output current at Vds = -1 V. Long term voltage stressing revealed an overall resistance decrease of the transistor channel under a constant bias with the open gate. On the contrary, repetitive gate switching increased the overall channel resistance.