Dermal tattoos in biomedicine: Emerging platforms for sensing and therapy.

Dermal tattoos are emerging as a novel class of skin-integrated biomedical platforms that extend beyond body decoration into functional sensing, monitoring, and therapeutic applications. In contrast to conventional biomedical devices, wearable systems, and epidermal electronics, dermal tattoos reside within the dermis, where they can access interstitial fluid, achieve stable tissue integration, and remain protected from surface contamination and mechanical disruption. Although this field is still in its infancy, recent studies have demonstrated the potential of dermal tattoos for a broad range of biomedical uses, particularly in sensing and diagnostics. Reported platforms include colorimetric, fluorescent, photoresponsive, living, and electrophysiological dermal tattoo systems for monitoring biomarkers, electrolytes, ultraviolet exposure, and physiological electrical signals. More recently, dermal tattoos have also begun to expand into treatment, including self-powered bioelectronic systems for wound healing and transient bioresorbable therapeutic interfaces. This review summarizes recent advances in dermal tattoos for biomedicine, focusing on sensing and therapy, along with their materials, fabrication methods, and readout strategies. It also compares dermal tattoos with conventional, wearable, and epidermal systems, and discusses their key opportunities, challenges, and future directions. However, most reported dermal tattoo platforms remain at the proof-of-concept stage, and their clinical translation is still limited by scarce in vivo validation, lack of standardized benchmarking, and limited long-term safety data.