Microneedle

Microneedles are tiny needles arranged on a patch or array, with typical lengths from 25 to 900 micrometers. Their goal is to breach the stratum corneum, the skin’s outer barrier, to deliver drugs or extract biomarkers with minimal pain and reduced needle-stick risk. They can be fabricated in various forms: solid microneedles that create microchannels; hollow microneedles that inject liquid formulations; dissolving or biodegradable microneedles made from polymers or sugars that disintegrate after insertion; and coated microneedles where drug is applied to the needle surface. Materials include metals such as stainless steel and titanium, silicon, and a range of polymers such as PLA, PLGA, poly(ethylene glycol), chitosan, and carbohydrate-based structures.

Manufacturing uses microfabrication techniques including lithography and etching for solid/silicon devices, and molding or 3D printing for dissolvable forms. Applications span transdermal drug delivery for vaccines, insulin, pain relief, and cosmetic actives; diagnostic and monitoring uses include sampling interstitial fluid for biomarker analysis. Dissolving microneedles can offer improved stability for vaccines and easier storage.

Advantages include reduced pain compared with hypodermic needles, potential for self-administration, low sharps waste, and rapid onset for certain drugs. Limitations include limited vehicle capacity (small doses), potential skin irritation or infection risk if not sterile, dosing variability, and regulatory hurdles. Ongoing research aims to expand drug compatibility, enhance delivery efficiency, and achieve robust, scalable manufacturing.