This study introduces the first steel micro fuel cells with enclosed channel flowfield made by laser additive manufacturing. These are also the first microfluidic devices with enclosed channels made from stainless steel by additive manufacturing. One important benefit of such fabrication methods is ultrafast prototyping, which we made use of in this study to optimize the performance of our fuel cells. The fabrication process consists of preparing a 3D model using a suitable computer-aided design software and then uploading the model file to the laser additive manufacturing machine. This process requires minimal manual intervention. The use of stainless steel as the fabrication material results in extremely durable, robust, chemically and thermally stable devices. Micro fuel cells with three different stainless steel flowfields were fabricated and characterized, two of which with enclosed channels, and one with traditional open grooves. Both enclosed channel flowfield fuel cells produced significantly higher power and current densities compared to the open groove counterpart: the maximum current density obtained was 1.515 A cm(-2) and maximum power density was 363 mW cm(-2). (C) 2016 Elsevier Ltd. All rights reserved.