A polymeric microneedle has been developed for drug delivery applications. The ultimate goal of the polymeric microneedle is insertion into the specified region without failure for effective transdermal drug delivery. Mechanical failure of various geometries of microneedles by axial load was modeled using the Euler formula and the Johnson formula to predict the failure force of tapered-column microneedles. These formulas were compared with measured data to identify the mechanical behavior of microneedles by determining the critical factors including the actual length and end-fixed factor. The comparison of the two formulas with the data showed good agreement at the end-fixity (K) of 0.7. This value means that a microneedle column has one fixed end and one pinned end, and that part of the microneedle was overloaded by axial load. When the aspect ratio of length to equivalent diameter is 12:1 at 3 GPa of Young's modulus, there is a transition from the Euler region to the Johnson region by the decreased length and increased base diameter of the microneedle. A polymer having less than 3 GPa of stiffness would follow the Euler formula. A 12:1 aspect ratio of length to equivalent diameter of the microneedle was the mechanical indicator determining the failure mode between elastic buckling and inelastic buckling at less than 3 GPa of Young's modulus of polymer. Microneedles with below a 12:1 aspect ratio of length-to-equivalent diameter and more than 3 GPa of Young's were recommended for reducing sudden failure by buckling and for successfully inserting the microneedle into the skin.

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轴向力对聚合物微针机械失效的分析

聚合物微针已被开发用于药物输送应用。聚合物微针的最终目标是插入指定区域而不会导致有效的透皮药物递送。使用欧拉公式和约翰逊公式对轴向载荷对微针的各种几何形状的机械破坏进行建模，以预测锥形柱微针的破坏力。将这些公式与测量数据进行比较，通过确定包括实际长度和末端固定因素在内的关键因素来识别微针的机械性能。两个公式与数据的比较表明，在最终固定性 (K) 为 0.7 时具有良好的一致性。该值意味着微针柱具有一个固定端和一个销钉端，并且微针的那部分因轴向载荷而过载。当长度与等效直径的纵横比在 3 GPa 杨氏模量下为 12:1 时，由于微针的长度减少和基部直径增加，存在从 Euler 区域到 Johnson 区域的过渡。刚度小于 3 GPa 的聚合物将遵循欧拉公式。微针长度与等效直径的 12:1 纵横比是确定聚合物杨氏模量小于 3 GPa 时弹性屈曲和非弹性屈曲之间失效模式的机械指标。建议使用长度与等效直径的纵横比小于 12:1 且杨氏值大于 3 GPa 的微针，以减少因屈曲引起的突然失效并成功将微针插入皮肤。通过减少微针的长度和增加基部直径，存在从 Euler 区域到 Johnson 区域的过渡。刚度小于 3 GPa 的聚合物将遵循欧拉公式。微针长度与等效直径的 12:1 纵横比是确定聚合物杨氏模量小于 3 GPa 时弹性屈曲和非弹性屈曲之间失效模式的机械指标。建议使用长度与等效直径的纵横比小于 12:1 且杨氏值大于 3 GPa 的微针，以减少因屈曲引起的突然失效并成功将微针插入皮肤。通过减少微针的长度和增加基部直径，存在从 Euler 区域到 Johnson 区域的过渡。刚度小于 3 GPa 的聚合物将遵循欧拉公式。微针长度与等效直径的 12:1 纵横比是确定聚合物杨氏模量小于 3 GPa 时弹性屈曲和非弹性屈曲之间失效模式的机械指标。建议使用长度与等效直径的纵横比小于 12:1 且杨氏值大于 3 GPa 的微针，以减少因屈曲引起的突然失效并成功将微针插入皮肤。刚度小于 3 GPa 的聚合物将遵循欧拉公式。微针长度与等效直径的 12:1 纵横比是确定聚合物杨氏模量小于 3 GPa 时弹性屈曲和非弹性屈曲之间失效模式的机械指标。建议使用长度与等效直径的纵横比小于 12:1 且杨氏值大于 3 GPa 的微针，以减少因屈曲引起的突然失效并成功将微针插入皮肤。刚度小于 3 GPa 的聚合物将遵循欧拉公式。微针长度与等效直径的 12:1 纵横比是确定聚合物杨氏模量小于 3 GPa 时弹性屈曲和非弹性屈曲之间失效模式的机械指标。建议使用长度与等效直径的纵横比小于 12:1 且杨氏值大于 3 GPa 的微针，以减少因屈曲引起的突然失效并成功将微针插入皮肤。