Development of Medical Micro Needle Made of Biodegradable Material

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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.