Researchers have developed an easy-to-build, low-cost 3D nano­printing system that can create arbitrary 3D structures with extremely fine features. The new 3D nanoprinting technique is precise enough to print meta­materials as well as a variety of optical devices and components such as microlenses, micro-optical devices and meta­materials. “Our system uses a two-step absorption process to realize 3D printing with accuracy reaching the nanometer level, which is suitable for commercial manu­facturing,” said research team leader Cuifang Kuang from the Zhejiang Lab and Zhejiang University in China. “It can be used for a variety of applications such as printing micro or nano­structures for studying biological cells or fabricating the specia­lized optical waveguides used for virtual and augmented reality devices.”

Conventional high-resolution 3D nano­printing approaches use pulsed femtosecond lasers that cost tens of thousands of dollars. Now, Kuang and colleagues describe their new system based on an integrated fiber-coupled continuous-wave laser diode that is not only inexpensive but also easy to operate. “This new approach helps make 3D nanoprinting accessible to scientists, even ones who are not familiar with the optical systems typically used for this type of fabri­cation,” said Kuang. “It could eventually lead to low-cost desktop 3D nanoprinting devices that could offer precision nano­printing to anyone.”  

3D printing objects with a feature size of approxi­mately 100 nanometers typically requires two-photon absorption. This involves using expensive femto­second lasers to achieve precision 3D photon absorption that solidifies, or poly­merizes, a liquid resin that is sensitive to light. Recently, two-step absorption has been developed as an alternative to two-photon absorption developed by Vincent Hahn’s research team at Karlsruhe Institute of Technology in Germany. It uses a special photo­initiator – benzil – together with a single light source to create polymerization. In the new work, the researchers developed a simplified and faster 3D nanoprinting two-step absorption system that uses a 405-nanometer-wavelength inte­grated fiber-coupled laser.

For 2D or 3D printing with the new system, the laser beam from the single-mode polarization-maintaining fiber is collimated and directed onto galvanometric mirrors. It is then focused into the photo­sensitive material with a high-numerical aperture microscope objective. “The simple system does not need a large number of optical components to modulate the laser beam, which saves money and produces less optical aber­rations, or errors,” said Kuang. “It is also highly stable and compatible with most commercial micro­scopes.”

The researchers demonstrate their 3D nanoprinting system by using it at low speeds to print 2D line gratings and 3D woodpile nano­structures with a lateral period of 350 nanometers. Using a faster scan speed of 1000 micron per second, 2D gratings with sub-200-nanometer reso­lution and sub-50-nanometer linewidth can still be fabricated with laser power less than 1mW. The researchers are now working to improve the writing speed and quality of the technique while maintaining high resolution. This will make the system practical to use for even more appli­cations. (Source: Optica)

Reference: X. Liu et al.: High-resolution 3D nanoprinting based on two-step absorption via an integrated fiber-coupled laser diode, Opt. Lett. 48, 4300 (2023); DOI: 10.1364/OL.495286

Link: Research Center for Intelligent Chips and Devices, Zhejiang Lab, Hangzhou, China