Researchers from China’s Jiangnan University have developed a method to 3D-print complex shapes in mid-air, without the need for a supporting structure.
The team’s novel technique involves a quick-curing ceramic paste that allows for the creation of previously impossible designs.
Additive manufacturing, commonly referred to as 3D printing, traces its origins back to the streets of 1980s Japan when Hideo Kodama built what he called a “rapid prototyping device” that used ultraviolet (UV) lasers to cure resin.
Struggling to find the funds to further his research, Kodama fell short of patenting his invention, abandoning his vision before 3D printing became commercial.
Instead of the UV-activated resin tested by Kodama, the scientists at Jiangnan University used ceramics as their printing material.
Represented in some form or another in almost every industry, ceramics are renowned for having a plethora of useful properties – being heat- and wear-resistant, structurally stable and insulative – that makes them ideal for many electronic components.
However, ceramics are not without their disadvantages. Most ceramics are not ductile and are brittle or break when twisted or subjected to a stressful impact force, preventing the material from being machined and shaped without significant difficulty.
Jiangnan University researcher and lead scientist for the project, Professor Liu Ren, and his peers went about solving this dilemma by formulating a novel ceramic printing paste and an improved ultra-fast curing method.
The team’s quick-drying paste consists of multi-scale ceramic filaments ranging from 0.41 millimetres to 3.5 millimetres in diameter. The liquid ceramic material is highly-photosensitive and solidifies almost instantaneously when exposed to near-infrared (NIR) light.
The ceramic slurry reacts so rapidly to light that the substance can hold its shape in mid-air the moment it is extruded from the printer’s nozzle, allowing for the creation of intricate and complex mechanical designs, such as cantilever structures and torsion springs, according to the Hong Kong-based newspaper, South China Morning Post.
It also limits the need to print supporting structures for those design features that can’t bear weight. Often excess material used as support needs to be removed, which frequently leaves imperfections in the print quality.
The new technique brings many advantages, like reducing the post-production workload and reducing print times and material usage, according to Liu.
The team’s work, published in the peer-reviewed journal, Nature Communications, showed that NIR light achieved a deeper cure than the standard UV light widely used.
Curing depth under NIR – a measurement of light’s ability to penetrate the paste – was recorded at 3.81 millimetres after 3 seconds of light exposure. Liu’s research showed a curing depth of 1.02 millimetres was achieved after 103 seconds when UV light was introduced.
Liu successfully demonstrated the ability to print mixed ceramics when the team added agents like iron, chromium green and stabilised zirconia to the paste.
The inclusion of dye as well as changing the nozzle’s speed, pressure and size, could allow for the creation of objects with significantly improved aesthetics.
The team is hopeful the breakthrough will inspire further innovation in the relatively young field of 3D printing.
