[Show abstract][Hide abstract] ABSTRACT: A microdevice for blood plasma separation using capillary phenomenon has been proposed in this work. Blood plasma can be separated by microcapillary channels fabricated by silicon bulk- micromachining process. The 2 times 3 cm<sup>2</sup> device with 1 mm-thick consists of a silicon separation chip and a glass cover. The separation was relatively fast (less than 2 minutes) after a blood-drop (20 mul) was drawn into the channels until the flow stopped. The device was designed for collecting 1 mul of plasma. Due to the advantages in a small sample volume, no power consumption, made the device possible for a blood diagnosis on a chip which promises the applications in point-of-care testing (POCT).