On September 3, 2022 NASA (National Aeronautics and Space Administration) of USA announced that its first launch of the Artemis mission has been postponed again. The Artemis mission was the second moon landing program after Apollo program 1972. Why NASA’s first return to the moon was postponed once again? One of the reasons claimed by NASA is its rocket encountered the leak of liquid hydrogen fuel. The low temperature of liquid hydrogen fuel got rocket fueling equipment shrink significantly during fuel filling process, which easily caused fuel leak off the pipe gap. Nevertheless, what’s the relation between the fuel pipe leak and 3D printing?

Let’s see an contrastive rocket-launching case of SpaceX (a space transportation services company founded by Elon Musk).

SpaceX successfully carried out its 54th rocket launch on September 11, 2022, and its rocket was reused for the 14th time, setting a world-high record for reusable rocket. Why is the rocket of SpaceX cheaper in production yet more reliable in practical use than NASA's rockets? An important factor is that SpaceX dared to try cutting-edge technologies: 3D printing.

The valves and pipes used to control liquid hydrogen and oxygen in SpaceX rockets are 3D printed parts. The parts are integrally 3D printed, which improves the structural strength and air tightness and makes it less prone to fuel leakage; meanwhile, the cost of those 3D printing parts is reduced much more than that in traditional manufacturing.

3D printing explodes in industry fields

In the impression of many people, 3D printing is just a niche technology used to make plastic models or to do prototyping test. In reality, in recent few years, 3D printing has greatly expanded both in terms of application breadth and research depth. Let’s learn two major development directions of 3D printing technology at present.

Essentially, 3D printing is a process of material shaping. It offers build advantages for precise control of complicated geometry. To print out complex-structural parts with wonderful mechanical properties (such as lighter, stronger and more durable in use) is an application direction of 3D printing. Another application direction of 3D printing is to print out functional parts that have well kept functional properties (Luminescence, electricity discharge, heat transfer, etc.) of the original materials consumed by the professional 3D printers.

3D printing to fulfil structural demands on printed parts

The 3D printed valves used in the SpaceX rocket mentioned above, or the 3D printed bones and teeth implanted in the human body, are vivid cases of 3D printed parts that well fulfil structural demands from different individuals. Metals, ceramics, etc.  are the original structural materials used by the customized 3D printing devices. The 3D printing researchers' exploration direction is to print lighter, stronger and more durable structures.

An interesting case is that researchers from Tsinghua University even developed a new structural material with 3D printing technology on September 2022. We commonly know that 3D printer feeds on 3D printing materials to produce 3D model parts, but how could a 3D printer print out a new material with a new structure? Actually, it’s not a complex process. It was based on nanoscale 3D printing technology (3D-printing nanocrystals with light).

What makes this case more interesting is that another research team from City University of Hong Kong advanced this 3D printed nanocrystals in stiffness, strength and ductility by heating it under certain conditions. The advanced material takes on an ultra-hard 3D architecture that is comparable to metals and alloys!

3D printing to fulfill functional demands on printed parts

Many materials can emit light, discharge electricity, and transfer heat. Those materials’ sensitive chemical structures are easily destroyed under the high temperature 3D printing (such as when using FDM 3D printer) or under light conditions (such as when using resin 3D printer). Therefore, the research focus is how to optimize the 3D printing process and how to print these sensitive materials and keep their properties in the finally produced parts?

Also on September 1, a Tsinghua University team published a paper in the journal "Nature" in which researchers printed 3D models with a material called "quantum dots". "Quantum dots" are nanometer-scale granular fluorescent materials. Now there is a "quantum dot LCD TV", the colorful fluorescence of which is realized by this material.

This quantum dot material can only be processed in a plane in the traditional manufacturing process, and it is difficult to form a three-dimensional structure. In other word, in a traditional way, only a two-dimensional fluorescence image can be formed, but a three-dimensional fluorescence model cannot be formed. In this paper, the researchers developed a new 3D printing process to process quantum dot materials into various three-dimensional models at ultrafine resolutions (tens of nanometers).

How to do it? To make this material 3D printable, it is necessary to start at the molecular level, designing a chemical bonding mechanism that "sticks" the quantum dot particles together. The researchers added chemical structures like sticky hooks around the quantum dot particles. When illuminated by a special laser (an assembly of DLP 3D printing device), the quantum dot particles bond to each other under nanometer resolution. By constantly moving the focal point of the laser light, it is possible to print a three-dimensional structure in a liquid container teeming with quantum dot particles.

Through this process, the researchers printed three-dimensional models such as the gate and auditorium, all of which retained the fluorescence function of quantum dot materials. What is the use of this technique? In the future, this process can be used to print various photoelectric sensors. It must be a broad market opportunity.

Conclusion

You see, from high-performance structural demands to various unique functional material demands, 3D printing is setting off a new round of revolution in advanced manufacturing. Some people say that the impacts of 3D printing to the manufacturing industry in the 21st century is just like the impacts of the Ford assembly line to the manufacturing industry in the 20th century, 3D printing would bring about disruptive changes. 

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