Solid oxide fuel cell (SOFC) and electrolyser (SOE) performances can be enhanced significantly by increasing the densities of (electrode vertical bar electrolyte vertical bar pore) triple phase boundaries and improving geometric reproducibility and control over composite electrode vertical bar electrolyte microstructures, thereby also aiding predictive performance modelling. We developed stable aqueous colloidal dispersions of yttria-stabilized zirconia (YSZ), a common SOFC electrolyte material, and used them to fabricate 2D planar and highly-customisable 3D microstructures by inkjet printing. The effects of solids fraction, particle size, and binder concentration on structures were investigated, and crack-free, non-porous electrolyte planes were obtained by tailoring particle size and minimising binder concentration. Micropillar arrays and square lattices were printed with the optimised ink composition, and a minimum feature size of 35 mu m was achieved in sintered structures, the smallest published to-date. YSZ particles were printed and sintered to a 23 mu m thick planar electrolyte in a Ni-YSZ vertical bar YSZ vertical bar YSZ-LSM vertical bar LSM electrolyser for CO2 splitting; a feed of 9:1 CO2:CO mixture at 1.5 V and 809 degrees C produced a current density of -0.78 angstrom cm(-2) even without more complex 3D electrode vertical bar electrolyte geometries. (C) 2016 The Authors. Published by Elsevier Ltd.