Epidermal patches are multifunctional skin-interfacing platforms with applications spanning wound management, real-time biosensing, drug delivery, and tissue regeneration. Hydrogels play a central role due to their mechanical compliance, water-rich composition, and tunable physicochemical properties. Key design features flexibility, stretchability, self-healing, and self-adhesion, which ensure stable skin contact and device stability. Tailored electrical conductivity, enabled by conductive polymers, fillers, and novel fabrication strategies, allows seamless integration with bioelectronics for intelligent health monitoring. Fabrication innovations, such as 3D/4D printing, stereolithography, digital light processing, extrusion-based writing, inkjet printing, electrospinning, and microneedle-based platforms, allow precise spatial control and multifunctional integration. Emerging approaches, including AI-assisted biosensing, stimuli-responsive drug release, noninvasive skin metabolite monitoring, and biodegradable systems, further expand their potential. Applications range from infection-resistant wound dressings and minimally invasive drug delivery to acne therapy, cardiac patches, and hydrogel micropatch probes for skin metabolomics. Challenges remain in achieving scalable manufacturing, long-term durability, and material sustainability. Future development will converge intelligent hydrogel design, integrated biosensing, data-driven analytics, advanced metabolomics, and personalized transdermal therapeutic, transforming epidermal patches from passive materials into adaptive, closed-loop biointerfaces capable of sensing, decision-making, and on-demand intervention. By uniting therapeutic, diagnostic, and protective functions, hydrogel-based epidermal patches are set to revolutionize personalized healthcare.
Wang et al. (Mon,) studied this question.