Dec 7, 2016 | By Tess
Non-wobulated and wobulated DMD patterns
Researchers in Korea have demonstrated how a novel “wobulation” technique can enhance the resolution of nanostructures made through flow lithography. The technique uses Digital Light Processing (DLP) 3D printing technology, and could have many applications, including drug delivery, bioassays, cell carriers, tissue engineering, and authentication.
Flow lithography is a method used to continuously generate polymer microstructures. Up until now, however, scientists have remained somewhat limited in terms of the resolution level of the flow lithography nanostructures they’ve been able to create. Now, with the new wobulation technique developed and demonstrated by the team from Kyung Hee University in Seoul, they have been able to take that resolution up a notch.
As mentioned, the wobulation technique uses a DLP projector, which projects lithographic patterns onto a plane. Rather than just rely on the projected image’s automatic resolution, the researchers realized that by adding a second, overlapping projector frame at a slightly different position, the final frame would be of a much higher resolution. According to the research team, this revelation could mean quality advances even for existing DLP 3D printers.
To explain in a little more detail, DLP 3D printers are equipped with a tiny electro-mechanical device called a Digital Micromirror Device (DMD). The DMD, which consists of a number of tiny, controllable mirrors, is essentially responsible for the patterns of UV light that are projected onto the printing plane. As the research explains, the resolution of these projections is strictly tied to the pixel size of the DMD, and achieving resolutions as high or higher than other lithographic methods while maintaining a standard field of view has proved a constant challenge.
The wobulation technique, however, offers a potential solution to this problem of resolution and field of view. As Wook Park, a physicist at the Kyung Hee University, explains: “Wobulation works much like when two transparent, plaid backgrounds are stacked one above the other, the result would be a denser-looking plaid, but the square shape of the plaid is still obvious. If we instead shift one layer a bit with respect to the other, the ragged edge of the plaid pattern is much less obvious. In much the same way, we tried to better define the lithographic edge by exposing a UV pattern twice, staggering the second exposure with respect to the first, and by cutting the exposure time of each layer in half. Applying this wobulation technique we achieved an effect just as if a higher-resolution pattern was exposed for the whole exposure time.”
Overall, the wobulation technique has provided a way to increase the resolution of DLP projections without sacrificing the field of view—previously magnifiers were used to achieve higher resolutions, which inevitably reduced the field of view. The research, which was recently published in Applied Physics Letters, will help scientists improve DLP in bioassays, drug delivery, cell carriers, tissue engineering, and authentication. Using the technique, the team is hoping to ultimately create more complex 3D hydrogel microstructures, and eventually create a 3D printer that couples microfluidics and additive manufacturing techniques to make continuous microcarrier and biomaterial printing possible.
“One of the biggest challenges in developing 3D printers is improving the resolution,” Park added. “By applying wobulation to address that challenge, we expect to be able to improve the performance of already commercialized DLP 3D printers.”
Posted in 3D Printing Technology
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