Real‐time monitoring wound status and providing timely therapies with smart wound dressing is a promising way to treat wound infections and accelerate the healing process. Herein, to establish a closed‐loop monitoring and treatment system, a fully integrated, battery‐free, and wireless smart wound dressing for wound infection detection and on‐demand drug delivery is developed using flexible electronics. The smart wound dressing integrated with the near field communication module can realize wireless power harvest and data transmission, on‐site signal processing, and drug delivery control, through the miniaturized circuit and smartphone. The temperature, pH, and uric acid of the wound is detected simultaneously by the developed sensors to assess wound conditions. Meanwhile, the drug delivery electrode in the dressing is used to provide on‐demand infection treatment by the electrically controlled antibiotics delivery. Through in vitro antibacterial experiments and in situ animal studies, it is shown that the dressing can effectively inhibit bacterial growth and accelerate wound healing, which fully validates its effectiveness in the wound treatment. Utilizing the advantages of near‐field communication and flexible electronics, the battery‐free and integrated design of sensing and treatment provides a promising solution for the development of a closed‐loop biomedical system integrating monitoring, diagnosis, and therapy.

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Skin‐interfaced electrochemical sensing devices are widely developed for biochemical sensing at molecular levels. However, the sensing electrodes fabricated with photolithography or printing technique are hard to achieve high stretchability without special designs like serpentine shape. Also, most of them require wired connections with external electrochemical workstations for data acquisition or on‐board batteries to power the circuits, which largely restrain the flexibility, simplification, and miniaturization of the devices. Here, a battery‐free, wireless, and epidermal electrochemical system is presented for in situ biochemical sensing. The sensing component of the system is a stretchable electrode array all‐printed with soft polymer and conductive silver nanowires. The electrodes show stable electrical properties within strain range of 0–50%, without serpentine designs. The electronic component of the system is a fully integrated flexible circuit board with near field communication module, which enables wireless energy harvesting and data transmission with smartphones. The system demonstrates good performance in real‐time on‐body sweat analysis for simultaneous quantitative detections of glucose, hydrogen, sodium, and potassium. This battery‐free and wireless epidermal electrochemical system provides a simplified, miniaturized, and flexible solution for a wide range of biochemical platforms, including wearable and implanted bioelectronics.

Room-temperature ferromagnetism has been observed in Fe-doped PbTiO3 nanocrystals. The magnetism of the nanocrystals develops from diamagnetism to ferromagnetism and the paramagnetism on increasing nominal Fe doping concentration from 0to4mol%. Transmission electron microscope (TEM) and high-resolution TEM data indicate that Fe-doped PbTiO3 nanocrystals with the size of ∼100nm are organized to form a planarlike self-assembly via oriented aggregation. These assembled nanostructures effectively improve room-temperature ferromagnetism of the sample. The exchange interaction of ferric ions via an electron trapped in a bridging oxygen vacancy (F center) is employed to explain the ferromagnetism of Fe-doped PbTiO3 nanocrystals.

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