Dual-laser approach could reduce costs for high-resolution 3D printing

Researchers have developed a new two-photon polymerization technique that uses two lasers to 3D print complex, high-resolution structures. This advance could make the 3D printing process more cost-effective and help it to become more widely used in a variety of applications.

Two-photon polymerization is an advanced additive manufacturing technique that traditionally uses femtosecond lasers to precisely polymerize materials in 3D. Although this process is well suited for the production of high-resolution microstructures, it is rarely used in industrial manufacturing due to the high cost of femtosecond lasers.

In the journal Optics Express, the researchers show that the two-laser approach reduces the required power of the femtosecond laser by up to 50 percent compared to using a femtosecond laser alone.

“We combined a relatively low-cost laser emitting visible light with a femtosecond laser emitting infrared pulses to reduce the power requirement of the femtosecond laser,” said research team leader Xianfan Xu from Purdue University. “In this way, with a given femtosecond laser power, the printing throughput can be increased, leading to a lower cost for printing individual parts.”

The conventional two-photon polymerization process uses femtosecond lasers to initiate a photochemical process that reduces inhibitory species in the material before printing begins. The new process uses a low-cost laser for this purpose instead. The researchers combined single-photon absorption from a 532-nm nanosecond laser with two-photon absorption from an 800-nm femtosecond laser and found the right balance between printing and inhibition by the two lasers.

“3D printing with high resolution has many applications, including 3D electronics devices, micro-robots for the biomedical field and 3D structures or scaffolds for tissue engineering,” said Xu. “Our novel, 3D printing approach can be readily implemented in many existing femtosecond laser 3D printing systems.”

“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 starts,” said Xu. “We used a low-cost laser for this purpose instead.”

The team developed a mathematical model to understand the photochemical processes and calculate the combined effect of two-photon and single-photon excitation. This allowed them to identify the dominant processes that control how much the power of the femtosecond laser can be reduced while still achieving desirable printing results.

“This new printing approach could impact manufacturing technologies, influencing the development of devices across consumer electronics and health care sectors both now and in the future,” said Xu.

After fine-tuning the new approach, the researchers printed various 2D and 3D structures with reduced femtosecond laser power. The printed structures included detailed wood stacks as small as 25 × 25 × 10 µm as well as micrometer-sized buckyballs, chiral structures and cloverleaf nodes. The experimental results showed that the new method reduced the required power of the femtosecond laser by up to 80 percent for 2D structures and up to 50 percent for 3D structures.