Scientists at Edinburgh’s Heriot-Watt University have developed a new 3D printing technique that uses near-infrared (NIR) light to create complex structures with multiple materials and colours. According to the scientists, this advanced technique will revolutionise the manufacturing industry.
The team was led by Dr. Jose Marques-Hueso of Heriot-Watt University’s Institute of Sensors, Signals, and Systems in Edinburgh.
New 3D Printing Technique to Advance Manufacturing
The team accomplished in their effort to develop this new technique by modifying stereolithography, a resin-based 3D printing process, to push the boundaries of multi-material integration. In a traditional 3D printer, a blue or UV laser is applied to a liquid resin, which is then selectively solidified, layer by layer, to build the desired object. However, one significant disadvantage of this approach has been the limitations in material intermixing.
The scientists use an NIR light source capable of printing at much greater depths into the resin vat without the need to print in layers in this latest project.
The findings have enormous implications for industry, particularly those that rely on specialised parts, such as those in the health and electrical sectors.
“The novelty of our new method, which has never been done before, is to use the NIR invisibility windows of materials to print at a depth of over 5 cm, whereas the conventional technology has a depth limit of around 0.1 mm.”– Dr Jose Marques-Hueso
Dr Marques-Hueso explained, “The novelty of our new method, which has never been done before, is to use the NIR invisibility windows of materials to print at a depth of over 5 cm, whereas the conventional technology has a depth limit of around 0.1 mm. This means that you can print with one material and later add a second material, solidifying it at any position of the 3D space, and not only on top of the outer surfaces.”
He continued, “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, made from an entirely different material, inside this box, because the NIR laser will penetrate through the previous material as if it were invisible, because in fact it is completely transparent at the NIR.”
Dr. Adilet Zhakeyev, a PhD researcher at Heriot-Watt University who has worked on the project for nearly three years, added, “Fused Deposition Modelling (FDM) technology was already able to intermix materials, but FDM has a low resolution, where the layers are visible, while light-based technologies, such as stereolithography, can provide smooth samples with resolutions under five micrometres.”
According to the researchers, one critical component of their project has been the development of engineered resins containing nanoparticles that exhibit the phenomenon of optical upconversion. These nanoparticles absorb NIR photons and convert them into blue photons that solidify the resin. This occurrence is ‘non-linear,’ which means it can obtain blue photons mostly at the laser’s focus rather than all the way through it. As a result, the NIR can penetrate the material as if it were transparent, solidifying only the material within.
The new 3D printing method allows multiple materials with different properties, such as flexible elastomers and rigid acrylic, to be printed in the same sample, which is useful for many industries such as shoe production. The technique opens up a plethora of new possibilities, such as 3D printing objects inside cavities, repairing broken objects, and even in-situ bioprinting through skin.
Dr. Marques-Hueso also mentioned that they had previously developed a resin that could be selectively copper-plated. “By combining both technologies, we can now 3D print with two different resins and selectively cover one of them in copper using a simple plating solution bath. This allows us to create 3D integrated circuitry, which is very useful in the electronics industry.”
Despite the fact that this technology provides an exciting glimpse into the future, its costs are surprisingly low.
The machine, according to Dr. Marques-Hueso, can be built for less than £400. Dr. Marques-Hueso hopes to collaborate with businesses and further develop this technology with a wide range of results that support the claims of this technology.
The Engineering and Physical Sciences Research Council (EPSRC) has awarded £280,000 to the project, titled Multimaterial Stereolithography by Crosslinking through Luminescence Excitation. The study’s findings were published in the journals Applied Materials Today.
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