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The microneedle size mimicking a female mosquito's labium which almost collects blood painless is effective
to mitigate the injection pain for patients. The author has produced the microneedle production technique which
can produce arbitrary size. The microneedle production technique is to deposit the microneedle material on a
rotating wire substrate by a sputtering deposition method and etch the wire substrate by a chemical solution after a
heat treatment. In the result, a titanium microneedle was produced (outer and inner diameter : 50 μm and 25μm) in
the size mimicking that of female mosquito's labium. The inner diameter for the needle is decreased when outer
diameter is decreased, hence, the rigidity of the needle is decreased and the pressure drop by pipe friction is
increased. Therefore, microneedles to be able to mitigate the pain for the patient and decrease the pressure drop by
pipe friction should be designed.
In this study, the outer and inner diameters of 50 μm and 25 μm are defined as the basic dimension of the
microneedle. Those rigidity and pressure drop by pipe friction in "n" polygonal shape circumscribed and inscribed
for basic dimension in the microneedle are calculated. The best shape with "n" polygonal shape to satisfy
conditions that needle has rigidity enough to inject the skin without buckling and to decrease the pressure drop by pipe friction to be able to extract blood was searched. The pressure loss became small more than the negative pressure generated with SMA micro pump in n=6. Therefore, the microneedle with sexanglular shape(n=6) made by titanium(E=110.6GPa) can be injected into the skin without buckling and decreased the pressure drop by pipe friction.
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