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International Journal of Bioprinting Unique characteristics of 3D-printed microneedles

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Figure 7. 4D printing of bioinspired microneedle array using PμSL (projection micro stereolithography). Reproduced with permission from ref.
(Copyright © 2020, John Wiley and Sons). (A) Schematic illustration of the PμSL process. (B) Schematic illustration of 4D printing approach to program
deformation of horizontally printed barbs into a backward-facing shape. (C–E) Scanning electron microscopy (SEM) images of 4D-printed microneedle
array with backward-facing barbs.

stiffness. In contrast, 3D printing, particularly the widely the purpose of employing 3D printing for microneedle
used VP technology, primarily relies on commercially manufacturing. Some researchers have resorted to micro/
available biocompatible photosensitive resins, which nanoprocessing on 3D-printed microneedles, such as
are less versatile and more expensive. In addition, the sputtering and coating, to obtain metal or conductive
monomer and initiators contents in photosensitive resin polymer surfaces. 92,93 An ideal solution involves the use
materials influence the hardness of the final products, of conductive ultraviolet-curable resin. According to
making material selection more difficult. In some available research, conductive materials (such as resins
applications, microneedles must also be conductive, and containing metal- or carbon-based fillers) can be added to
most existing photosensitive resins have poor conductivity. methacrylate or acrylate-based resins, to act as conductive
To overcome this, a common approach involves using polymers for 3D-printed consumables. 136-138 However, the
3D-printed microneedles as molds before injecting them mechanical properties of composite materials are often
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with conductive materials. However, this method defeats compromised by crosslinking, thereby affecting the
Volume 10 Issue 4 (2024) 73 doi: 10.36922/ijb.1896