Andreas Friederich

Improving mechanical fatigue resistance by optimizing the nanoporous structure of inkjet-printed Ag electrodes for flexible devices

The development of highly conductive metallic electrodes with long-term reliability is in great demand for real industrialization of flexible electronics, which undergo repeated mechanical deformation during service. In the case of vacuum-deposited metallic electrodes, adequate conductivity is provided, but it degrades gradually during cyclic mechanical deformation. Here, we demonstrate a long-term reliable Ag electrode by inkjet printing. The electrical conductivity and the mechanical reliability during cyclic bending are investigated with respect to the nanoporous microstructure caused by post heat treatment, and are compared to those of evaporated Ag films of the same thickness. It is shown that there is an optimized nanoporous microstructure for inkjet-printed Ag films, which provides a high conductivity and improved reliability. It is argued that the nanoporous microstructure ensures connectivity within the particle network and at the same time reduces plastic deformation and the formation of fatigue damage. This concept provides a new guideline to develop an efficient method for highly conductive and reliable metallic electrodes for flexible electronics.

Fully printed tunable phase shifter for L/S-band phased array application

In this paper, a novel fully printed method is presented for fabrication of phase shifter devices, aiming for phased array applications. This technology offers a simple and low cost way compared to other available technologies. The proposed phase shifter contains tunable ferroelectric varactors in metal-insulator-metal (MIM) configuration, which are fully printed on top of a carrier substrate. The printed phase shifter exhibits a figure of merit (FoM) of 70°/dB at 1.72GHz and shows a high potential for an implementation in fully printed phased array antennas.

Inkjet printed BST thick-films for x-band phase shifter and phased array applications

This paper presents a novel method of inkjet printed Barium-Strontium-Titanate (BST) material for low-cost RF application. To demonstrate its capability in phased array antenna application, a compact continuously tunable load line phase shifter in the frequency range from 8 GHz to 10 GHz is realized. The BST thick-film is printed at the areas which interdigital capacitors are later patterned. A phase shift of 175° and the figure of merit (FoM) of 20° /dB at 10GHz are achieved. The size of the planer circuit is 8mm × 6mm.

Tunable Phase Shifter Based on Inkjet-Printed Ferroelectric MIM Varactors

Abstract This paper presents a new method for the fabrication of tunable multilayer ferroelectric components based on inkjet printing. Inkjet printing is a low-cost technology for selective film fabrication and has high potential for the preparation of tunable dielectric layers for radio frequency and microwave applications. With this technology, tunable metal-insulator-metal (MIM) capacitor is fabricated, that is composed of inkjet-printed Barium-Strontium-Titanate striplines and photo-lithographically structured gold electrodes. Compared to coplanar capacitors, such MIM varactors require significantly lower DC-voltage for tuning. By applying 20 V across a 1 μm-thick BST film, a tunability of 33% is achieved at 8 GHz and tunability of 60% by applying 50 V. To demonstrate the field of application of this MIM varactor, a tunable phase shifter is designed and fabricated at 8 GHz. A phase shift of 143° and a figure of merit (FoM) of 28°/dB are achieved by applying maximum 50 V tuning voltage.