Lithuania: Researchers Explore 3D Polymerization via Polarization Control on Nanoscale

As the 3D printing industry grows, so does the research and development effort. All around the world as you sit and read these words, scientists are busy making strides with innovations from bioprinting to replace cartilage and help with conditions such as osteoarthritis to creating new and helpful forms of hardware to benefit global infrastructure, like robotic 3D printers that extrude concrete. No matter where you look there’s progress and it’s often quite surprising, simply because we’ve been used to the way so many things have been done for so long—from the way roads are paved to how doctors perform back surgeries.

And if science is one of your interests, in combination with technology, then you are probably getting quite familiar with the word (or more properly, the prefix) nano. Printing at the nano scale is relevant for numerous applications whether that of medical or electronics.

Now, researchers at the Laser Research Center of Vilnius University are studying more efficient ways to 3D print, and they plan to progress far beyond the layering approach. With the use of ultrafast laser pulse based non-linear light-matter interactions, they are working to expand the technology significantly. Outlined in the article ‘Nanoscale Precision of 3D Polymerization via Polarization Control,’ published recently in Advanced Optical Materials, we are given a glimpse into new possibilities and expansion in additive manufacturing, with greater, and even unmatched, flexibility and versatility, the possibility to use a wide range of new materials, and even further capabilities for customization which should offer great impact to optical and scaffolding structures covering applications in:

• Telecommunications
• Electronics
• Lab-on-chip based devices
• Tissue engineering

They point out that while this is quite feasible in the lab, it can in reality become extremely expensive for transferring prototype equipment to industrial lines running around the clock.

Centering around nanolithography, the researchers zone in on how light polarization influences this in regards to 3D printing.

“Polarization effects in laser 3D nanolithography are employed to fine-tune the feature sizes in the structuring of photoresist,” state the researchers in their paper.

The key, according to the scientists, is in offering fixed conditions between laser power and beam scanning/sample translation speed while varying how the linear polarization is oriented. This allows for precision at the nanoscale. With the region that was changed retaining the same depth, the aspect ratio modulation of the polymerized features is enabled, with no beam shaping techniques or phase masks required—as demonstrated in figure one.

Figure 1. Variation of polymerized features at constant irradiation intensity and different polarization orientations in respect to direct laser writing direction (perpendicular, parallel, circular). Voxel dimension and aspect ratio can be tuned at nanoscale via polarization control.

“The influence of beam polarization orientation on laser processing has been thoroughly studied in the cases of conductive and dielectric solid targets,” state the researchers in their paper. “There are known effects of polarization on the scalar parameters of laser matter interaction, such as absorption coefficient and ionization rate.”

 

“It is also known that heat conduction flux (vector) in plasma might be dependent on the direction of the imposed field. In what follows, these effects are considered in succession: (i) accumulation from multiple pulses, (ii) effects of polarization under high-numerical aperture (NA) focusing, and (iii) the influence of the external high-frequency electric field on electronic heat conduction.”

The researchers performed a thorough analysis via 3D modeling and experiments to reveal:

• Polarization effects
• Influence on resolution
• Coupling between thermal gradient and polarization in DLW

The scientists were able to display their findings in 3D printing a woodpile photonic structure both with and without polarization correction. When circular polarization was employed for laser writing, the ‘filtering performance’ was shown to be completely accurate, as compared to the ‘non-corrected’ case which did not fare so well in the use of circular polarization. In conclusion, they found light polarization to be a crucial dynamic in expanding the flexible nature for optical 3D structuring of polymers. Discuss this new study further in the Research on 3D Polymerization forum over at 3DPB.com.