A microfluidic device for separating liquid from the same liquid containing deformable particles without external sources of energy. The device includes: at least one transport channel (1) using various fluid-hydrodynamic principles in order to increase the amount of separated/obtained fluid; and at least one separating area (2) which diverts part of the fluid circulating through the transport channel towards at least one collection channel (3) or reaction chamber. The separating area (2) can include at least one array of pillars, the configuration of which maximizes the amount of fluid extracted at once. The depth and width of the collection channel (3) are adaptable according to the requirements of the test to be implemented. A filter is provided for separating plasma from a drop of blood in a highly efficient manner, which can be used in point-of-care testing systems.