Hollow metallic microneedles fabricated by combining bulk silicon micromachining and UV–LIGA technology

Abstract

As one of the promising research aspects in BioMEMS, microneedle technology has been widely applied in drug delivery. Compared with the solid microneedles, hollow microneedles can provide continuous delivering drugs. However, the fabrication processes and costs of the hollow microneedles are often complex and high accordingly. We propose a low-cost method to fabricate the hollow metallic microneedles, which contains procedures of using a wet method to etch silicon wafer to get the tapered cavities firstly, filling the tapered cavities with the SU-8 photoresist, developing the SU-8 to pattern the shapes of microneedles, and electroplating one metal in the patterns to form hollow metallic microneedles. According to the method, microneedles with different shape tips that include the triangular pyramids or the rectangular pyramids have been fabricated. In addition, these microneedles have been analysed using a finite element method and tested on artificial skins, which demonstrate the strength of microneedles is sufficient for piercing skins.

Microneedles: materials, fabrication, and biomedical applications

“…However, when being punctured into the skin, the fractures easily occur on the silicon microneedle, and the fragmented needle stays in the body and the biocompatibility of silicon is poor, which leads to the adverse reactions such as inflammation in the human body. Therefore, improving the mechanical strength of silicon is one of the research directions of the silicon microneedles (Yan et al 2011 ). Narayanan et al coated a layer of gold on the silicon material by metal sputtering to improve the mechanical strength and biocompatibility of the microneedle array.…”

Research progress of physical transdermal enhancement techniques in tumor therapy

“…114,115 Currently, solid MNs are mainly cut directly from solid materials by laser cutting and mechanical/chemical etching methods, but can also be made by master mold casting and electroplating. 116…”

“…114,115 Currently, solid MNs are mainly cut directly from solid materials by laser cutting and mechanical/chemical etching methods, but can also be made by master mold casting and electroplating. 116 Effective transdermal drug application of PTET in solid MNs requires a two-step operation, in which the MNs are inserted into the SC and removed after a period of time to form an aperture of size equal to that of the MN. Drugs are coated on the surface of the skin where the MNs act or are about to act, allowing the drug to enter the deep layer of the skin through the micropores formed.…”

Microneedles based drug delivery systems: an updated review

“…Hollow Microneedle can be made from metal by using metal electrodeposition which are joined with the master mold [117][118][119][120][121]. Additionally, Hollow Microneedle can be designed by using two-phase electrodeposition in which the hollow shaft is produced by twice electrodeposition [122,123].…”