microneedles

Microneedles are arrays of micron-scale needles designed to puncture the outermost layer of the skin, the stratum corneum, with minimal penetration into the deeper dermis. They enable drug delivery and small-volume sampling while reducing pain and tissue damage compared with conventional injections.

Designs include solid, coated, dissolving, hollow, and hydrogel-forming microneedles. Solid needles create microchannels; coated needles carry drugs on their surface; dissolving needles are made from biocompatible polymers and dissolve to release payloads; hollow needles permit liquid flow.

Common materials include silicon and stainless steel for rigid arrays, and polymers such as polylactic acid, PLGA, chitosan, and sugar-based polymers for dissolvable devices.

Applications span transdermal delivery of vaccines and therapeutics, cosmetic and dermatological treatments, and minimally invasive sampling of interstitial fluid for diagnostics. Research also explores gene delivery and rapid-response patches for emerging infectious diseases.

Advantages include reduced pain and bleeding, potential for self-administration, improved patient compliance, and possibilities for controlled or depot delivery that bypasses the gastrointestinal tract and first-pass metabolism.

Challenges involve variability in skin penetration, risk of infection or irritation, mechanical failure, manufacturing and sterilization, patch integrity, and regulatory approval. Some microneedle products have reached clinical trials, with regulatory status varying by jurisdiction.

Manufacturing employs MEMS-based microfabrication, laser structuring, and polymer molding to produce solid, hollow, or dissolvable microneedle arrays at scale, with quality control addressing geometry, strength, and sterility.