Transparent Thermotherapeutic Skin Patch Based on Highly Conductive and Stretchable Copper Mesh Heater

Abstract In the present work, a stretchable transparent heater (STH) is developed consisting of a free‐standing serpentine copper (Cu) mesh attached to a semipermeable polyurethane (PU) film. The as‐prepared Cu mesh STH is of extremely low sheet resistance of 0.15 Ω sq⁻¹ at an optical transmittance of 82.5%. The electrothermal and mechanical properties of the fabricated STHs are systematically studied by both experimental measurements and theoretical simulations. The Cu mesh STH proves to be highly effective. For a size of 1 cm × 2 cm skin patch, it can generate temperature up to 120 °C in less than 30 s at only 0.7 V supplied voltage. The average temperature drop of the Cu mesh STH is only about 10% under 50% strain at a constant voltage. In addition to the efficient heating, the Cu mesh STH demonstrates high stability during long‐term repetitive heating and cooling cycles. Moreover, the STH is air permeable and highly conformable to skin. Its high transparency allows constant monitoring of skin condition during a healing process. As a proof‐of‐concept, a skin patch consisted of the Cu mesh STH is successfully applied to cure the epidermal tumor of lab mice, demonstrating its great potential for skin‐patched thermotherapy.