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.
Highlights
Microneedle arrays (MNAs) draw more and more attention due to their great prospective in various applications such as transdermal electroporation [1], transdermal drug delivery [2], dry biopotential electrodes [3] and penetrating neural electrodes [4]
microneedle arrays (MNAs) have poor/fair discreteness, meaning that the microneedles could not be separated with the substrate in terms of material
MNA with 190 μm is taken as example to exhibit fabrication process
Summary
Microneedle arrays (MNAs) draw more and more attention due to their great prospective in various applications such as transdermal electroporation [1], transdermal drug delivery [2], dry biopotential electrodes [3] and penetrating neural electrodes [4]. Discrete MNAs, which means the microneedles are different from the substrate in terms of their materials, are needed to fabricate this kind of flexible penetrating electrode via a transferring method. The electron discharge machining (EDM) method is presented to manufacture stainless steel MNAs [12] These approaches could be considered as reductive manufacturing of the substrate. MNAs have poor/fair discreteness, meaning that the microneedles could not be separated with the substrate in terms of material. Silicon is widely used in fabricating MNAs due to its versatile tailoring process and high tensile strength, compared with other microneedle materials [14]. An alternate method is proposed in order to fabricate discrete MNA with tunable height-pitch ratios, which involves a KOH-dicing-KOH process
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