The new needle has an inner diameter of around 25 microns and an external diameter of 60 microns, which is about the same size as a mosquito's mouthpart. Its size and the fact that it works by suction, makes it painless. To compare, a conventional syringe needle has an outer diameter of around 900 microns.Unfortunately, it seems it is not designed for taking blood for CBC, BMP, PTT, etc:
Its size compared to earlier models also means that surface tension effects are exploited further, and the same capillary flow that draws water up into trees helps draw blood into the microneedle.
The researchers have calculated that their needle can extract 5 microlitres of blood per second. This volume is sufficient for measuring blood-sugar levels in diabetics using a glucose sensor that can be attached to the needle in a "wristwatch" design.via BoingBoing