A surprise benefit is unveiled by the method of printing metals at the nanoscale using 3D technology.

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September 21, 2023 This article has been reviewed according to Science X’s editorial process and policies. Editors have highlighted the following attributes while ensuring the content’s credibility: fact-checked peer-reviewed publication trusted source proofread by Emily Velasco, California Institute of Technology Late last year, Caltech researchers made a groundbreaking discovery – a new fabrication technique for printing microsized metal parts with unprecedented precision. The technique allowed for the creation of metal objects with features as thin as three or four sheets of paper. Now, the team has taken their innovation even further, pushing the boundaries of what is possible with 3D printing. They have successfully developed a method to print objects a thousand times smaller – a mere 150 nanometers, comparable to the size of a flu virus. This remarkable achievement opens up a world of possibilities for nanoscale engineering. What makes this discovery truly astonishing is the realization that the atomic arrangements within these tiny objects are disordered, which, on a larger scale, would render them weak and of low quality. However, at the nanoscale, these unordered atomic structures actually enhance the strength of the parts. Prof. Julia R. Greer and her team at the Kavli Nanoscience Institute at Caltech have been at the forefront of this groundbreaking research. Their findings have been published in the prestigious journal Nano Letters. The new fabrication technique builds upon their previous breakthrough but has been reimagined and adapted for the nanoscale. However, working at such a small scale poses unique challenges, as the manufactured objects are not visible to the naked eye and are extremely delicate. The process begins with the creation of a photosensitive cocktail comprising a hydrogel, a type of water-absorbent polymer. This cocktail is selectively hardened using a laser to create a 3D scaffold in the desired shape of the metal objects. In this study, the team focused on creating tiny pillars and nanolattices. The hydrogel parts are then infused with a solution containing nickel ions, saturating the structure with metal particles. Next, the parts are heated, burning away the hydrogel, leaving behind metal ions that have oxidized (bound to oxygen atoms). In the final step, the components undergo a chemical process to remove the oxygen atoms, converting the metal oxide back into a metallic form. It is during this step that the fabricated parts gain their unexpected strength. The complex thermal and kinetic processes that occur during this transformation result in a microstructure characterized by defects and irregularities. Traditionally, these defects are considered detrimental to the strength of a material. However, the team discovered that in nanoscale metal objects, these defects actually strengthen the structure. When a pillar is defect-free, failure occurs catastrophically along the grain boundaries – the interfaces between microscopic crystals that make up the material. But when defects are present, failure cannot easily propagate between grain boundaries. This distributed deformation enhances the overall strength of the material. Wenxin Zhang, the lead author of the research and a graduate student in mechanical engineering, explains, “Usually, the deformation carrier in metal nanopillars – a dislocation or slip – propagates until it can escape at the outer surface. But in the presence of interior pores, the propagation terminates at the surface of a pore, rather than continuing throughout the entire pillar. It is harder to nucleate a deformation carrier than to let it propagate, explaining why the present pillars may be stronger than their counterparts.” Prof. Greer believes that this is one of the first demonstrations of 3D printing of metal structures at the nanoscale, marking a significant milestone in the field of nanotechnology. The ability to fabricate metal components with such precision at this scale opens up new possibilities in a wide range of applications, from medicine to electronics. The nanoscale objects created through this technique have the potential to revolutionize industries and drive innovation in ways we have yet to imagine. As the field of nanoscience continues to advance, we can expect even more exciting discoveries and breakthroughs to shape our future.

Title: The Surprising Discoveries Enabled by Nanoscale Additive Manufacturing

In a groundbreaking study led by researchers from the California Institute of Technology, a new approach to nanoscale additive manufacturing has yielded unexpected results. Contrary to initial concerns, the researchers found that the hierarchical microstructures produced through this method were not detrimental, but rather advantageous.

The potential applications of this process are vast and varied. One of the most exciting possibilities is the creation of catalysts for hydrogen production. Hydrogen is a clean and renewable energy source, and effective catalysts are crucial for its widespread adoption. With this new manufacturing technique, the production of such catalysts can be greatly enhanced.

Additionally, this method offers a solution for the development of storage electrodes for carbon-free ammonia and other chemical compounds. Ammonia is an important resource in various industries, including agriculture and energy. By utilizing hierarchical microstructures, the storage of ammonia becomes more efficient and sustainable.

Moreover, the researchers highlight the significance of this approach in the creation of essential components for various devices. These applications range from sensors to microrobots and heat exchangers. The ability to manufacture intricate microstructures at the nanoscale opens up new possibilities for designing and improving such devices.

At the onset of the study, the researchers expressed concerns about the potential limitations of the microstructures produced. However, their worries were proven unfounded. The hierarchical nature of the microstructures, rather than hindering their functionality, actually enhances their performance. This unexpected outcome has revolutionized the approach to additive manufacturing and instilled renewed confidence in its potential.

The research, published in Nano Letters, details the suppressed size effect observed in nanopillars with hierarchical microstructures. The findings provide a wealth of insights into the capabilities and advantages of nanoscale additive manufacturing. The study paves the way for future advancements in the field while expanding the scope of applications for this innovative technique.

As we delve deeper into this era of technological advancements, it is crucial to celebrate and learn from discoveries that challenge our preconceived notions. The journey of the researchers from initial concern to triumph stands as a testament to the power of innovation and the importance of embracing unexpected outcomes. With each breakthrough, we inch closer to a more sustainable and efficient future, powered by nanoscale additive manufacturing.

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