蚊子口针刺入皮肤的刺入力分析

Insertion Force of Mosquito Fascicle Penetrating into Human Skin

蚊子能够依靠一个大长径比的高弹性、高强度的天然"微针"——口针无痛地刺入人体皮肤并吸食血液,且刺入过程中从未发生过任何强度问题。本文设计1套高精度微力测量系统对蚊子口针刺入皮肤的刺入力进行在体测量。测量结果表明,蚊子口针刺破皮肤时的刺入力仅约16μN,而且蚊子在进一步的刺入皮肤过程中,口针作用力还将进一步减小并保持在一个极小的值(甚至接近零)附近上下波动,而采用同样实验方案测量的特制人造针头(尖端曲率半径仅约1μm)的刺入力可达165mN,且随着刺入深度的增加人造针头作用力还将继续增加。通过对蚊子口针的刺入机制分析,发现蚊子口针的微纳观结构及特殊的刺入方式是使其刺入皮肤超级省力的根本原因。该研究结果可为微针给药系统及微针的优化设计提供一定的帮助。

A mosquito uses a natural ＂microneedle＂ system called fascicle, with a large ratio of the length to the diameter and high flexibility and strength, to painlessly penetrate into human skin and suck blood. The strength of natural ＂microneedle＂ system has never problem in the penetrating process. A set of force measurement device with high precision of micro-Newton is designed to measure the insertion force to understand the penetrating process of mosquito fascicle into human skin. The measured results show that the penetrating force of mosquito fascicle into skin is approximately 16μN. In addition, it has also been found that after the mosquito fascicle tip penetrates into the surface of skin, the force of the mosquito＇s fascicle penetrating deeper into the skin will decrease as the insertion depth increase, and then levels out at a surprisingly low mean force （even almost be zero）. While the insertion force of an artificial needle is 165mN, the force of the artificial needle penetrating deeper into the skin will continue to increase. The study on the insertion mechanism of the mosquito fascicle shows that the mosquito＇s micronano-structure fascicle and its amazing oscillation inserting skill make it easily penetrate into human skin with a surprising low force. The results are helpful for the optimum design of the microneedles and transdermal drug delivery system.