As a part of the development of a minimally invasive hollow microneedle designed to mimic a mosquito proboscis, we evaluated the relationship between the needle inner diameter (ID) and blood sucking performance. If the ID is thinned to reduce pain upon piercing skin, blood could clog the tube owing to coagulation, and a sufficient volume of blood might not be obtained. In this study, laser stereo-lithography is used to easily fabricate microtubes of several sizes, at 20–50 μm ID and a fixed length of 500 μm, through which human whole blood is sucked by a vacuum pump. The results indicate that the ID of the tube must be at least 20 μm to prevent hemolysis and at least 50 μm to enable extraction of 200 μL of blood, which is necessary for general blood tests. Moreover, anticoagulant coating applied on the inner wall prevents the clogging of blood and increases the volume of extracted blood.

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