New 3D printing techniques are poised to advance manufacturing


May 31, 2023

(Nanowerk News) Scientists have developed a sophisticated technique for 3D printing that will revolutionize the manufacturing industry.

The group, led by Dr Jose Marques-Hueso of the Sensors, Signals & Systems Institute at Heriot-Watt University in Edinburgh, have created a new method of 3D printing that uses near-infrared (NIR) light to create complex structures containing multiple materials and colors.

They achieved this by modifying a 3D printing process known as stereolithography to push the boundaries of multi-material integration. A conventional 3D printer will typically apply a blue or UV laser to a liquid resin which is then solidified selectively, layer by layer, to create the desired object. But the main drawback of this approach is the limitation in mixing the ingredients.

The research results have been published in Current Applied Materials (“Upconversion 3D printing enables single immersion multi-material stereolithography”). text (a) the “bridge” is printed with a single material; (b) two-color “bridge under another bridge”; (c) two-tone “grid within grid”; (d) tri-color prints; and (e) flexible/rigid molds. (© Today’s Applied Material)

What’s different about this latest project is that the scientists used a NIR light source that was able to print much deeper into a vat of resin, and without the need to print in layers.

These findings hold tremendous opportunities for industries, especially those that rely on specialist parts such as in the health and electricity sectors.

Dr Marques-Hueso explains: “The novelty of our new method, which has never been done before, is that it uses a NIR translucent window material to print at depths greater than 5 cm, whereas conventional technologies have a depth limit of around 0.1 mm. This means you can print with one material and then add a second material, compacting it at any position in the 3D space, and not just over the outer surface.

“For example, we can print a hollow cube that is mostly sealed on all sides. We can then come back later and print an object, which is made of a completely different material, inside this box, because the NIR laser will penetrate the previous material as if it were invisible, because it is actually very transparent in NIR.”

Dr. Adilet Zhakeyev, a PhD researcher at Heriot-Watt University who has been working on the project for almost three years, added: “Fused Deposition Modeling (FDM) technology can already mix materials, but FDM has low resolution, where layers are visible, while technology based light, like stereolithography, can provide fine samples with resolutions below five micrometers.”

The scientists say a key component of their project is the development of an engineered resin containing nanoparticles that exhibit the optical conversion phenomenon. These nanoparticles absorb NIR photons and convert them into blue photons, which solidify the resin. This incident is ‘non-linear’, meaning that it can acquire the blue photon mostly at the focus of the laser, and not as it passes through it. For this reason, NIR can penetrate deep into materials as if they were transparent and only solidify the material within.

New 3D printing methods allow several materials with different properties to be printed on the same sample, for example flexible elastomers and rigid acrylics, useful for businesses such as shoe production. This technique opens up a myriad of new possibilities, including 3D printing objects in cavities, restoration of damaged objects, and even in-situ bioprinting through the skin.

“In the same research project, we have previously developed a resin that can be selectively plated with copper,” continues Dr Marques-Hueso.

“Combining the two technologies, we can now 3D print with two different resins and selectively cover only one of them with copper using a simple coating solution bath. In this way, we can create integrated circuits in 3D, which is very useful for the electronics industry.”

While this technology offers a glimpse into an exciting future, the cost is very low.

Dr Marques-Hueso said: “The obvious advantage of this technique is that a complete machine can be built for less than £400. Some of the other advanced technologies using lasers, such as Two-Photon Polymerization (2PP), require expensive ultrafast lasers of tens of thousands of pounds, but this is not our case as our specialist materials allow the use of inexpensive lasers.”

He concluded: “Now that we have results to back up our claims, we look forward to partnering with businesses and developing this technology further.”


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