3D printing reveals nanostructured light emission

The team of Dr. Jaeyeon Pyo at the Korea Electrotechnology Research Institute (KERI) has become the first in the world to reveal patterns of light emission from 3D printed nanowires, which has been published as a cover article in the prestigious scientific journal ACS Nano.

Higher resolution in display devices means more pixels in a given screen size. As pixel density increases, movies and images are displayed with greater precision and detail. In this regard, ongoing research aims to produce smaller light-emitting devices, from the micrometer scale (one millionth of a meter) to the nanometer scale (one billionth of a meter).

As the size of light-emitting devices decreases to hundreds of nanometers, distinct changes in the light-matter interaction occur, resulting in different emission patterns compared to macrostructures. Therefore, the understanding of light emission from nanostructures is an essential prerequisite for the practical application of nanoscale light-emitting devices.

KERI’s research team dedicated to display research using nanophotonic 3D printing technology¹⁾ for years, for the first time in the world they discovered patterns of highly directed light emission from 3D printed nanowires.

^{1) A technology for the implementation of photonic devices using a high-resolution 3D printing method at the nanoscale. Fabrication of nanoscale photonic structures in 3D architecture is achieved by directly writing functional inks formulated from various optical materials. This technology is expected to bring innovations in ultra-high resolution displays, security printing, data storage and more.}

Typically, it is challenging to uniformly produce light-emitting materials of desired sizes at specific locations using conventional chemical or physical vapor deposition methods. However, KERI’s 3D printing technology allows for precise diameter control by limiting the opening of the print nozzle, enabling the reliable fabrication of light-emitting materials at desired locations with a wide range of sizes (diameters from 1/10,000 to meter to 1/10 millionth of a meter).

The team of Dr. Jaeyeon Pyo observed and experimentally measured the patterns of light emission from the specimens²⁾ precision fabricated using nanophotonic 3D printing technology, ranging in size from nanometer to micrometer scale. The team also performed simulations of electromagnetic waves for in-depth analysis and cross-validation of their arguments.

^{2) Sample: A sample prepared for experiments and analysis.}

As a result, when the size of light-emitting materials becomes as small as 300 nanometers in diameter, the internal reflection of light disappears due to spatial confinement, leading to straight propagation of light in one direction. Consequently, the light emission pattern becomes highly directional. Typically, light propagates through different paths within a given internal structure, resulting in broad emission patterns as they overlap. However, in nanowire structures, only a single path exists, leading to the observed highly directional emission pattern.

The observed multi-directional attribute can significantly improve the performance of displays, optical storage media, encryption devices and more. Macro-structures with broad emission patterns can suffer from optical crosstalk when densely integrated, causing overlapping or blurring of signals. In contrast, nanowires with highly directional emission patterns allow clear separation between signals from each structure at high densities, eliminating distortions in representation or interpretation. The highly directed emission of nanowires makes them suitable for high-performance devices, as experimentally demonstrated by the KERI team.

This research was published as a cover article for excellence in ‘ACS Nano’, a top tier SCI journal in the field of nanoscience with a JCR impact factor of 15.8.

Dr. Jaeyeon Pyo stated, “Research on nanoscale optical physics is challenging, especially due to the difficulty in sample preparation, which is often high-cost and time-consuming. Our contribution shows that the 3D printing method can be a platform versatile for the study of optical physics due to its simple, flexible and low-cost characteristics.” He added, “This research will significantly contribute to the latest display technologies and quantum physics, which are part of South Korea’s National Strategic Technology Nurture Plan.”

The research team anticipates that their contribution will attract significant interest in the fields of virtual reality (AR, VR), beam projectors, optical storage media, photonic integrated circuits, encryption technologies, and security printing, where ultra-thin materials small ones that emit light can be used. They intend to continue investigating various optical phenomena occurring at the nanoscale using the 3D printing method, exploiting its free-form fabrication capability.