The high rotational speeds of the paperfuge can be exploited in diagnostic sample preparation via centrifugation. a, A plastic capillary loaded with 20 μl of human blood. b, A capillary placed into hollow plastic capillary holders (with ends sealed) attached to the paperfuge. c, Kinetics of red blood cells (RBC) and plasma separation. d, Separation of 8 μl of blood plasma (per capillary) from whole blood occurred in less than 1.5 min. Error bars in c and d represent the standard deviation calculated from eight independent trials conducted by two users (one male, one female), which highlights the consistency and reproducibility of the haematocrit and plasma values. e, The quality of the plasma evaluated using microscopy, revealing 100% pure plasma; scale bars are 10 μm.