Source: Jiangsu Laser Alliance
The creation of complex ceramic or glass structures using stereoscopic lithography, a type of 3D printing, has long been limited by the length of the process’s back end, which can be as long as two days.Now, a new technology has reduced that to less than five hours.The team published their findings in Communications Materials on May 20.
Stereo lithography USES CAD files to print objects from powder suspended in a liquid.Lasers are shone into liquid and powder suspensions (called colloids) from which objects can be built layer by layer.(Milk, for example, is also a gel, but it is made from milk fat suspended in water.)
Lasers cause some light-sensitive particles to join together, or “cross link”, to form a layer of particles embedded in a polymer (the long chain of molecules), a hardening process known as “curing”.In effect, the laser “writes” the layers in the liquid suspension, and the layers print each other out, creating a 3D object of binder and powder.Ceramic or glass stereoscopic lithography has the potential to produce previously unachievable parts with more precise and complex geometries, including hollow objects or parts with complex internal structures that can reduce weight and maintain strength.This complexity of ceramic and glass design offers many new biomedical, structural and energy applications.
Uv-curable suspension research has caused wide attention, because it to raise material manufacturing (such as digital light processing, the laser stereo lithography, projection stereo lithography mask projection stereo lithography, enclosed and ultraviolet auxiliary directly into), in situ solidification, reduction of material manufacturing, three-dimensional micro template copying, fiber production and stop time moment to design the complex structure of ceramic and glass components is indispensable.To date, a variety of light curing suspensions have been designed.Although the simplest methods of dispersing inorganic particles directly into photocurable monomers using free radical initiators, many studies have also focused on solvent-containing multicomponent mixtures to control suspension viscosity and to form pores in a controlled manner in photocurable green bodies that are conducive to the deadhesion of the polymer.However, these require a very slow and complex degreasing/sintering process to avoid crack formation/structural collapse due to the large number of bubbles caused by monomers in the suspension.For example, the degreasing and sintering process of raw SiO2 parts made from traditional photocurable SiO2 suspension may take 48 hours, which is not conducive to improving manufacturing efficiency.The use of photocured ceramic polymers is also an effective way of three-dimensional structure of ceramic/glass parts, just like the use of photocured ceramic suspensions.
The new concept of photocurable suspension is proposed by the researchers, which requires only a small amount of organic additives to rapidly degrease and sintering the obtained photocurable green.In a radical departure from the traditional approach, the researchers proposed an optically triggered interparticle network formation reaction in a stable non-aqueous suspension with a small number of monomers (see figure below).
The 3D structure of transparent silica glass assembly is realized by means of rapid heating profile of interparticle optical cross-linked suspension.Photo credit: Yokohama National University
To prove their concept, the researchers wanted to make clear glass.The special colloidal formulation USES silica particles modified by polyethylene imine, a polymer, and oleic acid, a fatty acid found in many animal and vegetable fats or oils.These particles are then mixed with a photoinitiator (a formulation that is sensitive to light and initiates curing) in an alcohol-based solvent and initiates curing.
Crucially, the formula also allows for a smaller than normal amount of monomers (particles that can be cross-linked) and encourages more cross-linking of other particles than in traditional glass and ceramic lithography.In general, a large number of monomers require a slow degreasing and sintering process because the rapid combustion of monomers produces gases that threaten the structure of the object.By using only a small amount of monomers in the colloid, the researchers successfully obtained degreasing and sintering time reduced to less than five hours.