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Research Highlight: Geiger

Energy Conversion via Metal Nanolayers

The Geiger group recently reported a kinetic-to-electrical energy transducer using nanolayers formed in a single step from Earth-abundant elements. The method utilizes large-area physical vapor deposition (PVD) onto rigid or flexible substrates that can be readily scaled to arbitrarily large areas. In addition to flowing aqueous droplets across the nanolayers, current is shown to be created either with linear flow of salinity gradients or with oscillatory flow of a constant salinity. The operational requirement of having to move a dynamically changing electrical double layer (a “gate”) across the nanostructure identified in prior approaches is confirmed for the structures and augmented by a need for electron transfer within the thermal oxide nanooverlayers terminating the metals that was identified with Caltech collaborator Tom Miller III. The simplicity of the approach allows for rapid implementation in various fields, including implantable applications in vivo, while PVD of metal nanolayers onto a range of other polymers surveyed opens the door to transducers operating in 3D structures prepared, for instance, by 3D printing. Despite these exciting possibilities, the authors caution that the underlying mechanism needs to be further investigated, for instance, by specifically following the charge-carrier motion in real time and space. Provisional patent applications have been filed. The paper appeared in PNAS vol 116, pages 16210-5 (2019). NU student authors are Mavis Boamah, now Linus Pauling Distinguished Postdoctoral Fellow at Pacific Northwest National Laboratory, graduate student Emilie Lozier, and Paul Ohno, now Eric and Wendy Schmidt Science Fellow at Harvard University, undergraduate student Catherine Walker, and Caltech graduate student Jeongmin Kim. The work was featured on the BBC World Service, Smithsonian Magazine, Big Ten News, Northwestern Now, and a number of national and international trade journals.



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