Viscoelastic Inks for Direct-Write Microfabrication of Single-Chamber Micro Solid Oxide Fuel Cells With Coplanar Thick Electrodes

Abstract

Single-chamber micro solid oxide fuel cells (SC-µSOFCs) with coplanar electrodes were fabricated using a robotically controlled direct-write microfabrication approach. Viscoelastic, gel-based inks were employed to create homogeneous electrodes of controlled width and interelectrode distance as well as uniform cross-sectional thickness. Electrode powders, NiO-YSZ (yttria-stabilized zirconia) for the anode and (La_0.8Sr_0.2)_0.98MnO₃-YSZ for the cathode, were first dispersed with a cationic polyethyleneimine solution. Polyacrylic acid was added to induce a fluid-to-gel transition. The rheology of the fabricated inks was characterized. The inks were then extruded through cylindrical micronozzles and deposited onto YSZ electrolyte substrates using a robotic deposition apparatus. Thickness and width of the sintered electrodes were close to the diameter of the extrusion nozzle. The improved shape retention of the deposited electrodes also enabled the fabrication of continuous electrodes with square cross-section. The cathode adhered very well to the electrolyte during sintering. However, the mismatch between the thermal expansion coefficient of anode and electrolyte seems to cause detaching and breaking of the anode so that electrochemical characterization of the fabricated cells was not yet possible.