title: An Improved Manufacturing Approach for Discrete Silicon Microneedle Arrays with Tunable Height-Pitch Ratio.
abstract: Silicon microneedle arrays (MNAs) have been widely studied due to their potential in various transdermal applications. However, discrete MNAs, as a preferred choice to fabricate flexible penetrating devices that could adapt curved and elastic tissue, are rarely reported. Furthermore, the reported discrete MNAs have disadvantages lying in uniformity and height-pitch ratio. Therefore, an improved technique is developed to manufacture discrete MNA with tunable height-pitch ratio, which involves KOH-dicing-KOH process. The detailed process is sketched and simulated to illustrate the formation of microneedles. Furthermore, the undercutting of convex mask in two KOH etching steps are mathematically analyzed, in order to reveal the relationship between etching depth and mask dimension. Subsequently, fabrication results demonstrate KOH-dicing-KOH process. {321} facet is figured out as the surface of octagonal pyramid microneedle. MNAs with diverse height and pitch are also presented to identify the versatility of this approach. At last, the metallization is realized via successive electroplating.
authors.affiliation: Science and Technology on Electronic Test & Measurement Laboratory, North University of China, Taiyuan 030051, China. wangrenxin@nuc.edu.cn.|Key Laboratory of Instrumentation Science & Dynamic Measurement, Ministry of Education, North University of China, Taiyuan 030051, China. wangrenxin@nuc.edu.cn.
authors.forename: Renxin
authors.initials: R
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Institute of Microelectronics, Peking University, Beijing 100871, China. wei_w77@163.com.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Institute of Microelectronics, Peking University, Beijing 100871, China. zhhli@pku.edu.cn.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Li
keywords: KOH etching; discrete; microneedle; octagonal pyramid