Manufacturing technology
With low upfront investment costs, it can be used to create both single-material and multi-material objects, making it especially well-suited to complex structures with several different parts. “Due to the ease of adding powder materials of different sizes and compositions to the polymer ink, VIPS-3DP has an advantage over many other 3D printing techniques without specialised equipment,” explains Dr Yong Huang, a professor in the University of Florida’s department of mechanical and aerospace engineering. Although VIPS-3DP could be used across multiple sectors, medical devices manufacturers are especially well positioned to see the benefits. One day, the technology could become the go-to method for manufacturing porous medical implants, such as those used within bone tissue engineering. As Huang adds, 3D printers are also adept at manufacturing ceramic components, common in artificial bones and joints along with dental replacements.
Just a phase
Like many other 3D printing methods, VIPS-3DP is classed as a ‘direct-ink writing’ (DIW) technique, which involves dispensing ‘ink’ out of small nozzles to build up 3D structures layer-by-layer. The ‘ink’ in question is a kind of polymer-based liquid, which needs to solidify rapidly as soon as it’s laid down. There are several ways of accomplishing this
goal, but one way is via so-called ‘phase separation’. In essence, when you separate the ink into two ‘phases’ – one of which contains a concentrated solution of polymers – the newly deposited filaments will begin to solidify. This, in turn, can be achieved through various means. One is using evaporation-based methods, while another is through immersing the polymer solvent in an antisolvent bath.
While these techniques are widely used, they
aren’t always optimal. As the researchers detailed in their paper, published in April in the journal Nature Communications, immersion-bath printing can be an arduous process with additional steps needed at the end. Generally speaking, the 3D printing community is looking for something greener, simpler and cheaper. With that in mind, the researchers tried a new approach: a vaporous non-solvent mist (VIPS-3DP). This technique proved highly successful in tests, leading them to believe that VIPS-3DP has the edge in terms of “printability, process and material selection”. According to the University of Florida, this technology has now been granted two patents. Its development was supported through funding from federal agencies, including the National Science Foundation and the Department of Energy.
Medical Device Developments /
www.nsmedicaldevices.com
Applications and advantages So how does VIPS-3DP differ from what manufacturers are using currently? As Huang explains, phase separation techniques may not be new – but VIPS-3DP has some unique features. “First, the use of non-volatile and recyclable chemical solvents to prepare polymer inks for printing minimises the contamination due to volatile compounds,” he says. “It also enables green manufacturing by solvent recycling.”
Second, because the printing process takes place at room temperature, energy usage is kept to a minimum. You may need to introduce some additional sintering steps after printing (i.e. compacting and solidifying the material), which consume additional energy, but the printing process itself is extremely efficient. This is good news from an environmental standpoint. Third, and perhaps most importantly, VIPS-3DP is not reserved for polymer printing alone. You can, after all, also use VIPS-3DP to print materials such as ceramics and metals, widely used within the medical devices field.
“VIPS-3DP can be easily expanded beyond the printing of polymeric inks,” is how Huang emphatically puts it. “Colloidal inks of polymer solution-based metallic and ceramic suspensions can be successfully 3D printed in air without the need for auxiliary support.”
In practice, a manufacturer looking to pursue this approach would start by taking the metal or ceramic powder and mixing it with an applicable polymer. They might be looking to create a composite material, in which case the mixture would remain as it is. Alternatively, the polymer would function as a binder, before being removed at the end. (In this instance, the delicate powdered material is known as a ‘green part’ whereas the binding material is known as a ‘brown part’.)
“The metal or ceramic powders are bound together by the solidified polymer as a green part after printing,” Huang says. “The green part can then go through a sintering process to remove the polymer matrix via thermal debinding. In other words, we heat the green part until the plastic turns into a gas.” Once the polymer has been removed, meanwhile, the powders are placed in a controlled environment oven. Here, the temperature is raised to approximately two-thirds of their melting point, which allows the particles to fuse together without significantly distorting their printed geometry. This means VIPS-3DP is a highly versatile technique when it comes to material selection. In their paper, the researchers describe printing “a wide variety” of stainless steel parts, along with copper- embedded polymeric structures, nickel-tungsten
$20.4bn
The size of the global 3D printing market in 2023.
Grand View Research 2.7m
The number of 3D printers in use worldwide by 2030.
Statistics 53
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