Twice Stretched Fabrication of Polylactic Acid Microneedle Arrays Using Drawing Lithography
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Online ISSN 2005-4602 Print ISSN 2234-7593
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Twice Stretched Fabrication of Polylactic Acid Microneedle Arrays Using Drawing Lithography Shingo Terashima1 · Chikako Tatsukawa1 · Masato Suzuki1 · Tomokazu Takahashi1 · Seiji Aoyagi1 Received: 6 January 2020 / Revised: 29 June 2020 / Accepted: 1 July 2020 © Korean Society for Precision Engineering 2020
Abstract A biodegradable poly-lactic acid (PLA) microneedle array composed of needles with a maximum length of 3 mm and an aspect ratio of up to approximately 18 was fabricated by drawing lithography. In the proposed fabrication method, the melted polymer is stretched twice. The approximate length is set in the first stretch, and the tip is sharpened in the second stretch. In the first stretch, by changing the thickness of the PLA sheet, PLA pillars with various lengths are fabricated. By defining the initial length of the needle, it is possible to set a wide range of aspect ratios and lengths. In the second stretch, it is possible to control the final aspect ratio and length of the needle, as well as the shape of its tip by changing the temperature and stretch speed of the PLA pillars. Finally, it was confirmed that the needle can pierce the surface of artificial skin and porcine skin. Keywords Microneedle · Drawing lithography · Poly lactic acid (PLA) · Biodegradable material · Biocompatible material
1 Introduction Drugs are typically administered through the skin with an injection or by oral ingestion. However, skin perforation is often painful to the patient, and when ingested, the drug may not be effectively absorbed because of the decomposition of the components in the digestive system [1]. These issues led to the development of transdermal patches; however, watersoluble substances with a molecular weight of 500 or more cannot penetrate the stratum corneum [2], and as a result, only drugs with a low molecular weight can be administered. To solve this problem, other low invasive methods that use microneedle arrays and are suitable for drugs with large molecular weight have been proposed [3, 4]. The most * Shingo Terashima r178030@kansai‑u.ac.jp Chikako Tatsukawa [email protected]‑u.ac.jp Masato Suzuki m.suzuki@kansai‑u.ac.jp Tomokazu Takahashi t.taka@kansai‑u.ac.jp Seiji Aoyagi aoyagi@kansai‑u.ac.jp 1
Kansai University, Yamate‑cho, Suita, Osaka 564‑8680, Japan
typical ones are depicted in Fig. 1. One of the methods uses solid microneedles (“solid needles” means “needles without holes”) to pierce the skin and to apply gel drugs. The needles hardly break while perforating the skin, and the drug can be administered effectively (Fig. 1a). The microneedle array fabricated in this study is mainly aimed for this purpose. The most common methods of producing solid microneedles, which are illustrated in Fig. 2, are as follows: (a) a metal plate is processed using a laser to fabricate the needle shape, which is folded at a right angle and set vertically to produce solid metallic needles [5]; (b) a silicon wafer is processed using photolith
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