Photochemically Induced, Polymer-Assisted Deposition for 3D Printing of Micrometer-Wide and Nanometer-Thin Silver Structures

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This award supports research that will contribute new knowledge related to additive manufacturing (AM) of metallic (silver) structures, promoting both the progress of new manufacturing technologies and advancing a broad range of scientific applications. AM is the process of making a three-dimensional object of virtually any shape from a digital computer model. The technique, often called 3D printing, has the potential to revolutionize the way things are made. Currently, there are many additive manufacturing processes to make metal parts. However, almost all additive manufacturing processes currently available require high-temperature processes, which can often cause damage to the products to be printed and deteriorate the product performance. Additionally, many of these processes are limited to macroscale components, with dimensions at the millimeter scale or above, due to size limitations for metal powder. This award supports fundamental research to help develop a room-temperature AM process that enables high-resolution printing without thermal damage. The new process will utilize solution-based layer-by-layer deposition to produce highly reflective and highly conductive metal microstructures directly from soluble metal salts. The metallic microstructures produced by this process have wide applications in semiconductor electronics, energy, healthcare, biomedical, aerospace, soft robotics, and automotive industries. Therefore, results from this research will benefit the U.S. economy and society. This research involves several disciplines including manufacturing, photochemistry, photonics, and materials science. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.Prevalent AM metal manufacturing mainly relies on thermal or laser assisted metal fusion or ink-jet printing of metal powders and nanoparticles, and has serious limitations, including large feature sizes, rough surfaces, high optical/electrical loss, and incompatibility with soft materials. This research will fill this knowledge gap by exploring a new solution-based photochemically-induced polymer-assisted deposition process to allow scalable production of metal microstructures. The research team will introduce a three-dimensional molecular precursor, consisting of an interlaid network of polymers, metal salt, and reductants, that can turn into continuous metal films and structures upon ultraviolet illumination. The research team will build a model to study the fundamental chemical and physical aspects of the growth mechanism, design a series of experiments to verify the model, explore the fundamental limits of the critical dimensions of the printed structures, combine theoretical and experimental studies, and characterize the structural, optical, and electrical performance of the printed films. Further, we will apply this technique to a variety of substrate materials, including non-flat surfaces, to construct three-dimensional structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.