4D Printing of a Bioinspired Microneedle Array with Backward‐Facing Barbs for Enhanced Tissue Adhesion

Abstract

Microneedle (MN), a miniaturized needle with a length‐scale of hundreds of micrometers, has received a great deal of attention because of its minimally invasive, pain‐free, and easy‐to‐use nature. However, a major challenge for controlled long‐term drug delivery or biosensing using MN is its low tissue adhesion. Although microscopic structures with high tissue adhesion are found from living creatures in nature (e.g., microhooks of parasites, barbed stingers of honeybees, quills of porcupines), creating MNs with such complex microscopic features is still challenging with traditional fabrication methods. Here, a MN with bioinspired backward‐facing curved barbs for enhanced tissue adhesion, manufactured by a digital light processing 3D printing technique, is presented. Backward‐facing barbs on a MN are created by desolvation‐induced deformation utilizing cross‐linking density gradient in a photocurable polymer. Barb thickness and bending curvature are controlled by printing parameters and material composition. It is demonstrated that tissue adhesion of a backward‐facing barbed MN is 18 times stronger than that of barbless MN. Also demonstrated is sustained drug release with barbed MNs in tissue. Improved tissue adhesion of the bioinspired MN allows for more stable and robust performance for drug delivery, biofluid collection, and biosensing.

3D-printed microneedles in biomedical applications

“…The barbs possess a 200 μm base diameter with 450 μm length. Sudan I as a photoabsorber (PA), poly(ethylene glycol) diacrylate, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide as a photoinitiator (PI), and Mn ≈ 250 (PEGDA 250) as a monomer were used to produce MNs with curved barbs ( Han et al., 2020 ). One of the issues that adversely affects the surface quality of 3D-printed MNs is the layer-by-layer nature of the 3D printing process.…”

“…Polymer MNs were developed by μSLA 3D printing with programmed deformation (4D printing) to study their adhesive properties in the cutaneous system for application in biosensors and long-term monitoring and delivery systems ( Han et al., 2020 ). The fabricated MNs included curved barbs to improve adhesion capacity.…”

“…By tuning the curving thickness, angle, and material composition, the adhesion of MNs with barbs to the tissue was increased by 18 times compared with a needle without barbs ( Morde, 2018 ). The fabricated MNAs were tested to deliver a drug in an ex vivo chicken tissue ( Han et al., 2020 ).…”

Limpet Tooth‐Inspired Painless Microneedles Fabricated by Magnetic Field‐Assisted 3D Printing

“…[ 2–7 ] Among microfabrication technologies, 3D printing shows great promise for fabricating MNs with diverse geometric shapes for different functionalities. [ 5,8–11 ] However, it remains a challenge to use 3D printing technologies, such as fused deposition modeling (FDM), inkjet printing, and selective laser sintering, to fabricate microscale MNs with fine detail to the necessary degree of precision. [ 12–18 ] Thus, current 3D‐printed MNs largely rely on additional processing procedures, typically chemical etching, to further reduce the feature size and sharpen or refine the features.…”

Janus 3D printed dynamic scaffolds for nanodeflection-driven bone regeneration

“…printing. Examples have so far been limited to one-way, non-reversible morphological transformations that are induced via permanent crosslinking of the materials, heat or pH changes non-suitable for physiological environments 25,26,27 . Few examples exist of morphological transformations that are twoway, reversible and repeatable, and these are based on the use of magnetic, inorganic and nonbiocompatible materials that are not suitable for biological applications 28,29 .…”