To explore potential for the power density enhancement of solid oxide fuel cells by controlling the cathode-electrolyte interface in mesoscale, two-dimensional numerical simulations were conducted. In the simulation, a level set-based topology optimization technique was successfully coupled with the SOFC simulation based on a microscale model and was applied for the local optimization of the interface shape. The numerical results showed that the optimized shape of the cathode-electrolyte interface varied depending on the simulation conditions and that the cell performance could be improved by applying non-flat design to the cathode-electrolyte interface for the same amount of cathode/electrolyte materials. (C) 2010 Elsevier B.V. All rights reserved.