Plasmon-Mediated Transdermal Ultrasonic Photo-Elastic Patch for Efficient Drug Delivery

Transdermal permeation is often restricted by the stratum corneum, necessitating either chemical enhancers or wired sonophoresis hardware. A compact, flexible, laser-activated cavitation patch that converts nanosecond optical pulses into mid-frequency (≈100 kHz) ultrasound, generating inertial cavitation in a 1 mm-deep micro-reservoir directly above the skin, is demonstrated. A 50 nm gold (Au) film on a quartz disc serves as an opto-acoustic transducer and is encapsulated in an elastomer scaffold that conforms to curved surfaces, sealing the drug reservoir. Multiphysics modeling predicts peak pressures of ≈3 MPa at the laser focus and greater than 0.2 MPa at a 3 millimeter tissue depth; hydrophone and high-speed videography corroborate these values. Ex vivo porcine-skin assays show that a 3-minute exposure at 290 mW increases the cumulative flux of niacinamide eight- to tenfold and extends its penetration depth to ≈450 microns. At the same time, vitamin C reaches ≈650 microns with a temperature increase limited to below 3 °C. The battery-free architecture, sub-cm² drug induction sites, and raster-scan free wide area scalable delivery system fabrication position the device as a promising platform for on-demand dermatological therapy and precision cosmeceutical delivery.