Preparation of Microneedle Array Mold Based on MEMS Lithography Technology

Abstract

As a transdermal drug delivery technology, microneedle array (MNA) has the characteristics of painless, minimally invasive, and precise dosage. This work discusses and compares the new MNA mold prepared by our group using MEMS technology. First, we introduced the planar pattern-to-cross-section technology (PCT) method using LIGA (Photolithography, Galvanogormung, Abformung) technology to obtain a three-dimensional structure similar to an X-ray mask pattern. On this basis, combined with polydimethylsiloxane (PDMS) transfer technology and electroplating process, metal MNA can be prepared. The second method is to use silicon wet etching combined with the SU-8 process to obtain a PDMS quadrangular pyramid MNA using PDMS transfer technology. Third method is to use the tilting rotary lithography process to obtain PDMS conical MNA on SU-8 photoresist through PDMS transfer technology. All three processes utilize parallel subtractive manufacturing methods, and the error range of reproducibility and accuracy is 2–11%. LIGA technology produces hollow MNA with an aspect ratio of up to 30, which is used for blood extraction and drug injection. The height of the MNA prepared by the engraving process is about 600 μm, which can achieve a sustained release effect together with a potential systemic delivery. The height of the MNA prepared by the ultraviolet exposure process is about 150 μm, which is used to stimulate the subcutaneous tissue.

Microfluidic technology and its application in the point-of-care testing field

“…LIGA is a German abbreviation for Lithographie, Galvanoformung, and Abformung, meaning photolithography, electroforming, and molding. LIGA refers to the process of using X-ray lithography and micro-electroforming to manufacture precision molds and replicate microstructures in large quantities ( Khan Malek, 2006 ; Wang et al, 2021 ). LIGA is primarily used to manufacture microfluidic chips with a high aspect ratio.…”

“…It does not need synchrotron radiation X-ray lithography and a special X-ray mask, and this aspect is conducive to the mass production of micromechanical devices. According to the different process routes of UV deep lithography, quasi-LIGA technology can be divided into three types: multilayer lithography-LIGA, silicon deep etching-LIGA, and SU-8 deep lithography-LIGA ( Khan Malek, 2006 ; Wang et al, 2021 ).…”

Electropolishing and Shaping of Micro-Scale Metallic Features

“…LIGA and its related processes have significant applications in manufacturing micro-pumps, gear wheels, micro-connectors, and biomedical inserts [ 94 , 95 , 96 ]. Lithography is used widely for the patterning of micro-channels and features by using double electroplating to make micro-gears, sacrificial layers for micro-motors, micro-needle arrays, and micro-fiducial markers for determining micro-mechanical properties [ 97 , 98 , 99 , 100 ]. Its advantages for micro-fabrication over electric discharge machining are that it offers high-aspect ratio features, and the high straightness and planarity of sidewalls.…”

An overview of microneedle applications, materials, and fabrication methods

“…There have been many studies of microneedles for applications such as drawing blood and interstitial fluid (ISF) or delivering low and high molecular weight biotherapeutics, drugs, and vaccines through the skin. A wide range of microneedle structure, design, geometry, and microneedle array densities is manufactured using different rapid prototyping and microfabrication technologies such as deep reactive ion etching (DRIE) [ 2 ], lithography [ 3 ], hot embossing [ 4 ], and micromoulding [ 5 ]. In addition to microneedles for skin penetration, these microstructures have also been used in other sites of the body including the delivery of bioactive drugs into the eyes [ 6 ] and the insertion of molecules into cells using nanoneedles [ 7 – 8 ].…”