Abstract Variable-height, out-of-plane, convoluted microneedle arrays with high aspect ratio, tapered shafts, sharp tips, and smooth surfaces are required for applications where the microneedle heights must conform to a specific target geometry. Here, we show that it is possible to achieve such convoluted microneedle arrays on a Z-cut quartz substrate by a single wet etching step in saturated NH4HF2 at 80 °C. Due to the low etch rate of quartz, the procedure is based on carefully controlling the dimensions of every needle-like structure by properly dimensioning the masked area on top. In particular, we show that the mask dimensions for all the microneedles can be optimized via a combination of Level Set (LS) simulations of wet etching and an Evolutionary Algorithm (EA) to search the optimal dimensions. As an example, we fabricate two different microneedle arrays, where the needle heights follow two different spherical surfaces. Our experiments confirm that (i) the LS method correctly predicts the evolution of the etch front for microneedles etched on AT, BT and Z quartz cuts; and (ii) the LS + EA approach provides a suitable procedure to determine an optimal collection of mask sizes for the fabrication of convoluted microneedle arrays on the Z cut.

中文翻译：

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通过单步各向异性湿法蚀刻对平面外、可变高度、复杂的石英微针阵列进行基于仿真的优化

摘要 在微针高度必须符合特定目标几何形状的应用中，需要具有高纵横比、锥形轴、尖锐尖端和光滑表面的可变高度、平面外、回旋微针阵列。在这里，我们表明可以在 80°C 的饱和 NH4HF2 中通过单个湿法蚀刻步骤在 Z 切割石英基板上实现这种复杂的微针阵列。由于石英的蚀刻速率低，该过程基于通过正确确定顶部遮蔽区域的尺寸来仔细控制每个针状结构的尺寸。特别是，我们展示了所有微针的掩模尺寸都可以通过湿蚀刻的水平集 (LS) 模拟和进化算法 (EA) 的组合来优化，以搜索最佳尺寸。举个例子，我们制造了两种不同的微针阵列，其中针的高度遵循两个不同的球面。我们的实验证实 (i) LS 方法正确预测了在 AT、BT 和 Z 石英切割上蚀刻的微针的蚀刻前沿的演变；(ii) LS + EA 方法提供了一个合适的程序来确定用于在 Z 切割上制造回旋微针阵列的掩模尺寸的最佳集合。