Selection of the best shape for a micro painless needle

Abstract

Number of diabetics, including the ones who are likely to be diabetics, has been reported up to 22.1 million people in Japan, while it is amounted to 554 million worldwide according to International Diabetes Federation than (IDF). Diabetics measure their blood sugar level several times a day, and administer insulin in accordance with the measurement results for their treatment and prevention of complications. However, upon blood glucose measurement and administration of insulin, diabetics need to make a puncture in their skin by a needle, which requires complicated operation and pain. This is one of the reasons that diabetics neglect their treatment, that leads to the progression of symptoms and complications. Therefore, in order to reduce the burden of diabetics, we have been developing a titanium micro painless needle using a biocompatible material, titanium. It is necessary to consider pain, stiffness, and loss of pressure, in order to design a micro painless needle. First, we focused on a method to evaluate pain, and by using the method, factors that can be evaluated effectively on the pain of the needle during puncture was searched. Additionally, focusing on salivary α-AMY concentration fluctuation, it was confirmed that the pain evaluation method can be evaluated by stress referring. Next, maximum allowable outer diameter and maximum biological contact area was decided using the pain evaluation method obtained. Maximum allowable outer diameter was confirmed as φ95 [μm] ≤ X outer diameter <;φ100 [μm], and maximum biological contact area being 0.842 [mm2] or less. Finally, considering the results of pain, rigidity and pressure loss, the optimum shape of the micro painless needle for the purpose of improving rigidity and reducing biological contact area of the needle is to make it a regular pentagon. From the viewpoint of biological maximum contact area and second moment of area, it was confirmed that regular pentagon inscribed in a circle of outer diameter φ95 [μm], having inner diameter of φ44 [μm] is the best condition.