Accuracy and speed are often the big trade off especially when it comes to resin printers with their increasingly fine micron-level resolutions.
Researchers from Karlsruhe Institute of Technology (KIT), Heidelberg University, and the Queensland University of Technology (QUT) have published details on their successful demo of a method called lightsheet 3D microprinting, that maintains small voxel sizes while keeping a relatively high speed.
According to the researchers, using light-sheet 3D printing technology, the print time per part has now come close to typical manufacturing times found in injection molding.
The paper, titled “Light-sheet 3D microprinting via two-colour two-step absorption”, states that voxel volumes of less than 1 cubic micron are possible with non-linear optical systems in resin printing, but these often suffer from low printing speed or high cost.
Typical linear optical systems (projection methods such as LCD) print in the 100 cubic micron voxel size region, and so while they are fast, they are not so fine.
Using their system they were able to demonstrate printing with features 0.5 cubic μm voxel size. You can see this in the very thin cross members in the SEM image below. The team says that even thinner structures are possible with this method.
Pre-activated photoinitiator
In light-sheet 3D printing, blue light is projected into a container filled with a liquid photoresin, which is a mix of photoinitiator, scavenger and a multifunctional monomer.
The blue light projection comes from continuous-wave laser diodes at 440 nm wavelength, and this pre-activates the photoinitiator in the resin.
The graphic below shows continuous-wave laser diodes at 440 nm wavelength (blue) for projection and a continuous-wave laser at 660 nm (red) for the light-sheet . With this method, a peak printing rate of 7 × 106 voxels s–1 at a voxel volume of 0.55 μm3 was achieved.
The photoinitiator is only in this idle-intermediate electronic state for a finite time before it returns to its steady state, and so the time to print between layers is determined by this cycle between activated and pre-activated states. During this time the red continuous-wave laser for the light-sheet hits the still-activated resin, beginning the polymerization reaction by crosslinking the liquid monomers. The blue and red light are fired in sequence per layer.
The researchers demonstrated a return time of less than 100 microseconds, allowing for the high printing speeds. 0.5 cubic μm voxel size
The graph below shows how the lightsheet printing (labeled as “2SA” in the graph) compares to other printing methods such as SLS, CLIP, FFF and more).
The researchers state that with more sensitive resins, even lower-cost LEDS in their printers rather than the already cost-efficient continuous-wave laser diode option already installed in their current system.
The team hopes to scale up to printing structures measuring centimeters while maintaining these high speeds at low voxel resolutions.
You can read the full paper, titled “Light-sheet 3D microprinting via two-colour two-step absorption” at this link.
