3D printing fabrication process for fine control of microneedle shape

Abstract

Microneedle electrode (ME) is used to monitor bioelectrical signals by penetrating via the skin, and it compensates for a limitation of surface electrodes. However, existing fabrication of ME have limited in controlling the shape of microneedles, which is directly relevant to the performance and durability of microneedles as an electrode. In this study, a novel method using 3D printing is developed to control needle bevel angles. By controlling the angle of printing direction, needle bevel angles are changed. Various angles of printing direction (0–90°) are investigated to fabricate moldings, and those moldings are used for microneedle fabrications using biocompatible polyimide (PI). The height implementation rate and aspect ratio are also investigated to optimize PI microneedles. The penetration test of the fabricated microneedles is conducted in porcine skin. The PI microneedle of 1000 μm fabricated by the printing angle of 40° showed the bevel angle of 54.5°, which can penetrate the porcine skin. The result demonstrates that this suggested fabrication can be applied using various polymeric materials to optimize microneedle shape.

Determination of vat-photopolymerization parameters for microneedles fabrication and characterization of HPMC/PVP K90 dissolving microneedles utilizing 3D-printed mold

“…Following the determination of appropriate curing time for shapes A, B, C, and D, MN patches were printed utilizing different printing angles: 30°, 45° and 60°. The printing angle affected the height and width/diameter of the needles including sharpness owing to the distinct layers observed at each angle 9 as illustrated in Fig. 3 .…”

“…Furthermore, the square-based needle had a larger printing volume compared to the round-based needle, so the square-based needle required less material deposition than the round-based needle. Moreover, a high material deposition can be obtained by adjust the printing angle 9 , 15 . Nevertheless, the edges quality of the four different shapes of needle was not acceptable since all designs showed stair-stepped edges as demonstrated in Table 4 .…”

“…However, SLA can be used to construct solid MN with the desired height, diameter and shape, and those of 3D-printed solid MNs can be utilized to fabricate MN mold. Nowadays, vat photopolymerization had been reported for printing pyramidal and cone shape microneedles 7 – 10 by adjusting printing angle 7 , 9 , needle height 7 and needle to needle spacing 9 , 11 . However, there are three essential parameters, such as curing time 12 , printing angle 9 , 13 and anti-aliasing 14 that impacted needles appearance because these three vital parameters influence the size 12 , 15 , sharpness 13 , shape and smoothness of the needles 16 .…”