Rotate-to-bend setup for fatigue bending tests on inkjet-printed silver lines

Abstract

For the growing field of flexible electronics the performance of fabricated flexible devices during bending deformation has to be investigated in order to guarantee their resilience against small bending radii and bending fatigue. We report on a rotate-to-bend apparatus, which allows for arbitrary sequences of compressive as well as tensile bending and a wide range of selectable bending radii without applying additional strain. The electrical characterization can be conducted simultaneously with high speed measurement. We test the rotate-to-bend device on inkjet-printed conducting paths of Ag nanoparticles and Ag nanowires on various foil substrates. Fatigue bending cycles show that tensile deformation leads to a higher increase in resistance of the printed lines compared to compressive strain. This is caused by the higher tendency of microcracks to form during tensile bending. We also show the high negative impact of the substrate thickness on bending fatigue during full bending cycles. Here, Ag nanowires show superior fatigue behaviour compared to the nanoparticle lines due to their flexible, mesh-like network. The rotate-to-bend apparatus could become an efficient and inexpensive device for the testing of flexible devices.

Fully printed ZnO-based valency-change memories for flexible and transparent applications

“…A rotate-to-bend setup (figure S1 supporting information), inspired from Huber et al, was deployed to show the influence of cyclic bending of the PEDOT:PSS/ZnO/PEDOT:PSS memory cells on its electrical performance [26]. The memory cell is fixed by two clamps on each side, with one arm being able to rotate.…”

“…The distance of the clamps L is 6.45 mm, and the thickness d of the substrate is 125 µm. One full bending cycle consists of a symmetric flexure and a compression of the memory cell with a maximal bending angle β of ±54 • , resulting in a maximal bending radius r of 3.1 mm, determined by the following equation [26]:…”

Fully Inkjet-Printed Carbon Nanotube-PDMS-Based Strain Sensor: Temperature Response, Compressive and Tensile Bending Properties, and Fatigue Investigations

“…For investigating the piezoresistive properties of our CNTbased sensor, we use a lab-built rotate-to-bend apparatus [24]. It allows customized sequences of tensile as well as compressive bending operations by a stepping motor.…”

“…The latter has to be emphasized as many publications only report on tensile stress due to the difficulty to compress a flexible substrate in a controlled fashion. This can be overcome by utilizing our rotate-to-bend setup where the curvature during the rotation can be converted to a bending radius r as a function of [24]:…”