Development of Medical Micro Needle Made of Biodegradable Material

本研究的目的是研制一种外形模仿蚊子锯齿状的微针。这种针头可以有效地减少针刺入皮肤时的疼痛和恐惧，实现微量血液系统，实现糖尿病患者的便携式血糖水平测量系统等。结构材料采用可生物降解聚合物聚乳酸（PLA）。在这一年中，我们尝试了以下几个项目，并取得了成功的结果：1)建立了PLA材料微成型固体针的制造工艺，2)硅橡胶人造皮肤插入时的阻力估算，3)开发了准分子激光在PLA固体针上钻高宽高比孔的制造方法，4)毛细管力采血。对于1)，寻找注射温度和注射压力的最佳条件。结果表明，将温度设定在PLA的熔点以上，并将压力设定在注射机的允许最大值，可以实现具有一定刚性的针头，可以承受对人体皮肤的插入。对于2)，新开发了插入阻力测量系统。该系统采用了高性能的传感器，并结合了一个1自由度的线性级，所有的功能都是由个人电脑控制的。实验证明，尖头和细柄对于减小阻力是有效的。然而，锯齿形状对减小力的作用并不突出。对于3)，实现了直径为20微米、长度为1mm的高纵横比孔。至于4)，通过变焦显微镜观察，血液确实是从针孔里流上来的。

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.