Skin‐Inspired Low‐Grade Heat Energy Harvesting Using Directed Ionic Flow through Conical Nanochannels

Low‐grade heat energies are ubiquitous, and most of these energies are untapped as heated river water or seawater. Therefore, it is meaningful and valuable to extract the stored energies in the context of the energy crisis by using a simple device with low‐cost effectiveness. Here, a simple thermoelectric conversion system is shown using directed ionic flow through the biomimetic smart nanochannels, inspired by the human skin. The obtained power density of the nanodevice can ideally be 88.8 W m −2 with a membrane temperature gradient (Δ T ) of 40 °C. As proof of concept, it is demonstrated that the principle can be introduced into simple and portable prototypes to harvest low‐grade heat. Such a thermoelectric conversion apparatus provides a new venue for low‐grade heat harvesting. In addition, this self‐powered system may extend the electronic skin field and find applications in skin prosthetics.