‘You can 3D print one material through another, as if it were invisible’: New 3D printing technique

Scientists developed a 3D printing technique that could revolutionize manufacturing.

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

The researchers achieved this by adapting a 3D printing technique known as stereolithography, which is well-established and has been used to integrate multiple materials. Normally, a 3D printer uses a laser, either blue or ultraviolet, to solidify a liquid resin. The layers are then stacked to create the desired object. The main drawback to this method is the limited ability to mix materials.

The scientists have used a NIR-based light source that allows them to print at greater depths and without needing to use layers.

These findings offer tremendous opportunities to industry, especially those sectors that depend on specialist parts like the electrical and health sectors.

Dr. Marques Hueso says, “The novelty in our new method is that we use the NIR transparency windows of materials to be able to print to a depth greater than 5 cm. Conventional technology only allows a maximum depth of 0.1 mm.” It is possible to print one material and then add another, solidifying the second material at any point in the 3D space and not just on the outer surfaces.

“For example we can print an almost completely sealed cube on all sides.” We can return later to print another object made of a different material inside this box. The NIR laser will make it appear as though the old material was invisible because it is actually completely transparent in the NIR.

Adilet Zhakeyev is a Ph.D. research at Heriot-Watt University, who has been working on the project for almost three years. “Fused Deposition Modeling technology has a low-resolution, which makes the layers visible. Light-based technologies such as stereolithography can produce smooth samples with a resolution of under five micrometers.”

Scientists say that a critical component of the project was the development of engineered polymers containing nanoparticles that exhibit the optical upconversion phenomenon. These nanoparticles convert the NIR into blue photons which solidify resin. This “non-linear” phenomenon can only obtain blue photons at the focus of a laser and not while passing through it. This is why the NIR can penetrate deeply into the material and solidify the material inside.

The new method of 3D printing allows for multiple materials to be printed with different properties in one sample. For example, flexible elastomers can be combined with rigid acrylic. This is useful for many industries, such as the shoe industry. This technique offers a wide range of possibilities including 3D printing inside cavities, restoring broken objects and in situ bioprinting.

“In the previous research project we had developed a resin which can be selectively plated with copper,” says Dr. Marques Hueso.

Combining both technologies allows us to 3D print using two different resins, and then selectively cover one of them with copper by using a simple solution bath. We can make integrated circuitry 3D. This is a very useful tool for the electronics industry.

This technology is surprisingly affordable, even though it provides a fascinating glimpse of the future.

Dr. Marques-Hueso said, “A clear advantage of this technique is that the full machine can be built for less than £400. Some advanced technologies, such as Two Photon Polymerization (2PP), use ultrafast, expensive lasers.

Now that we can prove our claims with results, we are looking to partner with business and further develop this technology.

Journal of Research on the Environment and Development Advanced Engineering Materials.