Fig. 1: Architecture and eco-degradation of the self-powered iontophoretic–electrochromic patch (ITP-EC Patch).
a Device structure and working principle of the ITP–EC patch with a built-in Mg–MoO3 battery that drives iontophoretic delivery and the charge-correlated WO3 electrochromic indication of delivered dose in series. Ionic current (yellow arrows) crosses skin to deliver drug, while electronic current (blue arrows) powers the synchronized WO3 gauge, together forming a single closed electro-ionic loop for on-skin, dose-referenced readout. b Photographs of the ITP–EC patch showing the EC module in top view and the galvanic iontophoresis module in bottom view. The top view highlights the patterned WO3 EC layer (overlay red) and counter electrode (overlay blue) with a laminated electrolyte, and the WO3 appears deep blue after coloration. The bottom view shows the anode in red and the cathode in blue on the same flexible substrate. Dashed boxes mark active areas. Scale bar 5 mm. c Eco-degradation of the ITP–EC patch in aerated soil with oat seeds at 25 °C, kept moist by daily tap water. Images at 0, 21, and 42 days show intact EC and electrodes at 0 days, swelling and fragmentation with Mg corrosion by 21 days, and substantial degradation of metallic and EC components with small substrate remnants by 42 days; seed germination is unaffected. Scale bar 1 cm.
