The research team developed additive manufacturing (AM) technology based on hydrogel injection, and related research was published on Nano Letters

It is reported that the research team of California Institute of Technology has developed an additive manufacturing (AM) technology based on hydrogel injection, which uses two-photon lithography technology to produce 3D metal with a characteristic resolution of about 100 nm.

The relevant research is published in the journal Nano Letters, titled 'Suppressed Size Effect in Nanopillars with Hierarchy Microstructures Enabled by Nanoscale Additive Manufacturing'.

Keywords: additive manufacturing; Two photon lithography; Nickel; Nanomechanics; molecular dynamics
At the end of last year, researchers at the California Institute of Technology revealed that they had developed a new manufacturing technology that could print tiny metal parts as thick as three to four sheets of paper.

Now, the team has reinvented this technology, which can print objects a thousand times smaller than before: 150 nanometers, the size of a flu virus. During this process, the research team also found that the atomic arrangement inside these objects is disordered. However, in the case of nanoscale metal objects, this disordered atomic arrangement is 3 to 5 times stronger than similar sized structures with ordered atomic arrangements.

This new technology is similar to another technology announced by the team last year, but each step is redesigned to work at the nanoscale. However, this poses another challenge: creating invisible or difficult to manipulate objects.

The first step in this process is to prepare a photosensitive "cocktail" mixture, mainly composed of hydrogel, which is a polymer that can absorb water many times its own weight. Then, the mixture is selectively hardened with a laser to establish a 3D scaffold with the same shape as the desired metal object. In this study, these objects were a series of tiny pillars and nanolattices.

The hydrogel is then partially injected into an aqueous solution containing nickel ions. Once the mixture is saturated with metal ions, they will be baked until all the hydrogels are burned out. Although the remaining part has shrunk, it still has the same shape as the original one, and is completely composed of oxidized metal ions (combined with oxygen atoms). In the final step, oxygen atoms are chemically peeled off from the part, converting the metal oxide back into metallic form.

Researchers claim that during this process, all these thermal and dynamic processes occur simultaneously, resulting in a very, very chaotic microstructure. Defects such as pores and irregularities in the atomic structure will be observed, which are usually considered as defects with deteriorating strength. If you want to make something from steel, such as an engine cylinder block, you wouldn't want to see this microstructure because it greatly weakens the strength of the material.

However, their findings are on the contrary, weakening the strength defects of metal components on a larger scale actually enhances nanoscale components.

Researchers believe that this is one of the first demonstrations of 3D printing of nanoscale metal structures. This process can be used to manufacture many useful components, such as catalysts for hydrogen; Electrodes for storing carbon free ammonia and other chemicals; And the basic components of devices such as sensors, micro robots, and heat exchangers.

Source: Sohu