Exoshell-Assisted Fully Conformal Ultrasonic Facial Masks for Enhanced Transdermal Therapy

Improving skin condition has attracted growing public interest, motivating the development of wearable transdermal drug delivery systems. Ultrasound-assisted delivery enhances skin permeability noninvasively, but existing wearable devices, even highly stretchable ones, fail to achieve complete conformal contact with the complex concave-convex topography of the human face, limiting full-area treatment. Here, we present an exoshell-assisted fully conformal ultrasonic facial mask (FCUFM) that mechanically guides stretchable electronics to achieve intimate contact across the full facial surface. The engineered outer shells gently press the device onto the skin, ensuring stable conformity while maintaining low surface pressure for comfortable wear. This approach enables full (∼100%) midfacial coverage that far exceeds the value of ∼51% in the conventional bendable-stretchable approach. Optimized fabrication and encapsulation processes further enable scalable manufacturing suitable for medical applications. Electrical, acoustic, and thermal performances are systematically characterized at the device level. Cytotoxicity assays and histological analyses confirm biosafety, while enhanced drug delivery is demonstrated through Franz diffusion cell measurements and validated in human facial experiments. These results establish a scalable strategy for wearable therapeutic devices capable of conforming to complex three-dimensional biological surfaces, highlighting the potential of curvature-adaptive ultrasonic platforms for advanced transdermal therapy and personalized skin treatment.