Researchers have developed a new two-photon polymerization technique that uses two lasers to 3D print complex, high-resolution structures. The advancement could make the 3D printing process less expensive, allowing it to be used more widely in a variety of applications.
Two-photon polymerization is an advanced additive manufacturing technique that traditionally uses femtosecond lasers to polymerize materials in a precise, 3D manner. While this process works well for creating high-resolution microstructures, it has not been widely used in manufacturing because femtosecond lasers are expensive and increase the cost of printing parts.
“We combined a relatively low-cost laser that emits visible light with a femtosecond laser that emits infrared pulses to reduce the energy requirement of the femtosecond laser,” said research team leader Xianfan Xu of Purdue University. “In this way, the printing throughput can be increased for a given femtosecond laser power, leading to lower costs for printing individual parts.”
In the magazine of Optica Publishing Group Optics ExpressThe researchers show that the dual-laser approach reduces the femtosecond laser power required for 3D printing by as much as 50% compared to using a femtosecond laser alone.
“High-resolution 3D printing has many applications, including 3D electronic devices, microrobots for the biomedical field, and 3D structures or scaffolds for tissue engineering,” Xu said. “Our new 3D printing approach can be easily implemented in many existing femtosecond laser 3D printing systems.”
Finding the right laser balance
The new work is part of the research team’s efforts to continually improve the printing speed and reduce the printing cost of two-photon polymerization, which uses the phenomenon of two-photon absorption to precisely harden, or solidify, a light-sensitive material.
“In a conventional two-photon polymerization printing process, the femtosecond laser is first used to initiate a photochemical process that reduces the inhibition species in the material before printing begins,” Xu said. “We used a low-cost laser for this.”
The new approach combines single-photon absorption from a 532 nm nanosecond laser with two-photon absorption from an 800 nm femtosecond laser. To make this work, the researchers had to find the right balance between the printing and the inhibition caused by the two lasers. They did this by creating a new mathematical model to help them understand the photochemical processes involved and calculate the combined effect of two-photon and single-photon excitation processes. They also used the model to identify the dominant processes that determine how much the femtosecond laser power can be reduced while still achieving the desired printing results.
Print detailed structures
After refining the new approach, they used it to print a variety of 2D and 3D structures using reduced femtosecond laser power. These included detailed woodpiles measuring just 25 × 25 × 10 μm, as well as a micron-scale buckyball, chiral structure, and trefoil knot. Experimental results showed that the new method reduced the required femtosecond laser power by up to 80 percent for 2D structures and by up to about 50 percent for 3D structures.
“This new printing approach could impact manufacturing technologies and influence the development of devices in consumer electronics and healthcare, both now and in the future,” Xu said. The researchers are now working to further improve the printing speed and reduce the cost of 3D printing.
