Passive pump based on capillary force generated by gaps between microbeads for blood collection via microneedle

We propose a new passive pump for high-speed blood collection via ultra-narrow microneedle based on capillary force, in which the hydrophilized microbeads are three dimensionally integrated. The gaps between microbeads act as capillary pumps. Merits of this device are as follows: 1) blood is automatically sucked up when the microneedle reaches to blood vessel, 2) it is much smaller than most conventional syringe pumps. The pumping pressure is inversely proportional to the diameter of each capillary. Flow resistance of the pump decreases with the number of capillaries. Namely, a lot of fine capillaries are effective for increasing the flow rate. A developed pump successfully sucked up human blood via a microneedle (inner dia.; 30μm, length; 1 mm).