Development of Medical Micro Needle Made of Biodegradable Material

本研究的目的是研制一种外形为锯齿状的仿蚊微型针。该针可有效地减少穿刺皮肤时的疼痛和恐惧，实现微量血液系统，实现用于糖尿病患者的便携式葡萄糖水平测量系统等。作为结构材料，采用可生物降解的PLA（聚乳酸）聚合物。本年度内，本研究尝试了以下几个项目，并取得了成功的结果：1）利用PLA材料的微成型方法建立了固体针的制造工艺，2）估计了插入硅橡胶人工皮肤时的阻力，3）开发了利用准分子激光在固体PLA针上钻高纵横比孔的制造方法，4）利用毛细力采集血液。对于1），寻找最佳的注射温度和注射压力条件。结果证明，将温度设定为刚好高于PLA的熔点，并将压力设定为注射机的允许最大值，导致实现了具有插入人体皮肤的可靠刚性的针。针对2），新研制了一套插入阻力测量系统。该系统采用高性能的称重传感器，并将其与一个单自由度的线性工作台相结合，其所有功能都由个人计算机控制。研究表明，尖刃细柄结构对减小阻力是有效的。然而，锯齿形状对减小力的效果并不显著。对于3），实现了具有20微米直径和1mm长度的高纵横比的孔。对于4），通过变焦显微镜观察到血液确实在针孔内向上流动。

The aim of this research is the development of micro needle, of which outer shape is jagged imitating the mosquito. This needle would be effective for reducing pain and fear when penetrating a needle into skin, realizing a trace blood system, realizing a portable glucose level measurement system for diabetics, etc. As the structural material, biodegradable polymer of PLA (Poly Lactic Acid) is employed. In this year, the following items are tried and successful results are obtained : 1) establishment of fabrication process of solid needle by micro molding method for PLA material, 2) estimation of resistance force during insertion to artificial skin of silicone rubber, 3) development of fabrication method of drilling the high aspect ratio hole to the solid PLA needle by excimer laser, 4) sampling blood by capillary force. As for 1), optimal condition of injection temperature and injection pressure is searched. As the result, it is proved that setting the temperature to just above the melting point of PLA and setting the pressure to the allowable maximal value of the injection machine lead to realizing a surely rigid needle bearing the insertion to human skin. As for 2), a measuring system of resistance force during insertion is newly developed. This system employs a high performance load cell and combines it with a 1DOF linear stage, all function of which are controlled by a personal computer. It is proved that the sharp tip and thin shank is effective for reducing the resistance force. However, the effect of jagged shape is not prominent on reducing the force. As for 3), a hole with high aspect ratio of 20 micro meter diameter and 1mm length is realized. As for 4), it is observed by a zoom microscope that the blood surely runs up inside the hole of the needle.