This paper presents a capillary-driven microfluidic device that uses surfactant-added poly(dimethylsiloxane) (PDMS) to extract plasma from the blood without any external driving force. On the basis of the capillary phenomenon and filtration effect, plasma can be extracted through a planar crossflow filter using surfactant-added hydrophilic PDMS and SU-8-based microstructures. Because of the intrinsic hydrophobicity of PDMS, it is difficult to transport fluid in a PDMS microchannel using capillary action alone. In this study, we fabricated a microfluidic device with surfactant-added PDMS. The wetting property of PDMS was modified to be hydrophilic by mixing PDMS with a nonionic surfactant, Silwet L-77. As the hydrophilicity of PDMS increased, the filling rate of the fluid solution in the microchannel increased. The contact angles and passive capillary filling rates by surfactant concentration were compared, and the extraction of plasma was confirmed using a planar filter with various heights. Although the plasma extraction device exhibited limited throughput because of the use of a passive flow handling method, modifying the design and integrating sensors would make our device suitable for use in simple hematological tests of plasma. (C) 2010 Elsevier B.V. All rights reserved.