Fast Prototyping and Ex Vivo Evaluation of Dissolvable Millineedle Patches Made by Solvent Casting from CO₂ Laser Ablated Elastomer Molds

In this study, a highly feasible fabrication approach is explored to make flexible elastomer molds for producing transdermal patches comprising an array of millimeter-long dissolvable polymer needles. The millineedles (MilN), produced in both polyvinylpyrrolidone and carboxymethyl cellulose, are targeting efficient transdermal drug delivery. Employing a fast, inexpensive, and reproducible CO₂ laser ablation process, polydimethylsiloxane molds are successfully created measuring 10 × 10 mm², with arrays of conical cavities reaching depths of 1288.17 ± 128.93 µm. While this versatile fabrication technique is previously demonstrated for microneedles, it lacked a comprehensive performance evaluation of the produced needles. The study fills this gap by providing significant experimental data on the in vitro and ex vivo performance of the MilN patches. The applicability of the method is demonstrated by systematically casting and testing patches comprising various hydrophilic polymers and compounds. Mechanical testing underscored the resilience of MilN arrays, enduring compression forces up to 36 N for 30 s. Skin penetration efficiency, assessed in Parafilm M and porcine skin, revealed an insertion depth of ≈560 µm for polyvinylpyrrolidone MilN.