Photopolymer Microneedles: Geometry, Insertion, Fracture, Payload, Dissolution and Skin-Interface Qualification

Photopolymer microneedles combine sharp microgeometry, fracture resistance, payload architecture and a biological interface, so qualification must preserve the distinction between insertion mechanics and delivery function. This review examines printed solid, coated, hollow and dissolving microneedle concepts with emphasis on geometric fidelity, tip quality, insertion force, failure load, payload state and skin-interface evidence. Recent reviews document rapid expansion of 3D-printed microneedle manufacturing, while two-photon literature provides the microfabrication context for high-resolution structures. The central engineering ratio is not strength alone but structural margin relative to the force required for insertion under the intended skin model. For dissolving or drug-loaded designs, payload distribution and release add separate state variables. A qualification sequence is proposed that connects tip and shaft metrology to mechanical insertion, fracture margin, delivery or dissolution, and biological-interface controls without treating these endpoints as interchangeable.

ER-334 · Version 0.4.