Light emitting devices are typically manufactured as a sandwiched structure with a transparent electrode on top, which limits their adoption in a complex form-factor. Here, all-printed electrically driven lighting is demonstrated using the direct ink writing method. The electrochemiluminescence(ECL) emitting layer and electrodes are directly printed in a side-by-side electrode configuration. A 3D printable ECL ink is developed by incorporating silica nanoparticles as rheological modifiers to realize well-defined patterns with high structural integrity. Graphene-covered Ag electrodes embrace both the electrical conductivity and electrochemical stability for efficient ECL operation. This approach allows for intricate designs such as combs and spirals, and seamless manufacturing on diverse substrates including flexible films.

Advanced Materials Technologies 2302190 (2024) 

Light is diffracted when it meets small microstructures (around 1/1000 the thickness of a hair) at the wavelength level. Among the beautiful colors observed in nature, the wings of butterflies, the shells of beetles, and the feathers of peacocks are structural colors that are manifested by microstructures, not pigments. With the development of nano-processing technology, it has become possible to artificially implement structural colors, but 3D printing technology has had difficulty in implementing small microstructures that can diffract light. In this study, we showed that it is possible to implement and control structural colors by fabricating 3D diffraction gratings based on nano 3D printing technology. 3D printing method has the advantage of being less constrained than conventional nano-processing, so it can be applied to a variety of materials or forms of substrates at room temperature and atmospheric pressure. Structural colors by diffraction gratings can be utilized in transparent display technologies such as HUD in cars, smart windows/mirrors, and advanced display technologies such as AR, and diffraction gratings themselves can be used in various optical physics research.

ACS Nano 17, 13584 (2023)

Nanoscale integration is difficult on rough surfaces despite their ubiquity and usefulness. Paper is an emerging material system because it is renewable, flexible, and lightweight. However, owing to the rough surface of paper, it is difficult to use conventional nanoscale integration methods. Herein, nanoscale printing of CdSe/ZnS quantum dots on paper using a 3D printing method with surface adaptive control of the femtoliter meniscus is demonstrated. The approach allows the direct integration of light-emitting materials on the intact surface of paper with nanoscale lateral confinement. The 3D-printed nanostructures can be treated as a planar pattern of the nanoscale dots when viewed from the top. The individually addressable nature of the 3D printing method enables the equalization of the printed heights, which is essential for practical use in general planar systems. This method can be used in many areas that require paper such as paper electronics, security printing, biomedical engineering, and possibly other material systems with rough surfaces. 

Advanced Engineering Materials 23, 2100339 (2021)

The pixel is the minimum unit used to represent or record information in photonic devices. The size of the pixel determines the density of the integrated information, such as the resolution of displays or cameras. Most methods used to produce display pixels are based on two-dimensional patterning of light-emitting materials. However, the brightness of the pixels is limited when they are miniaturized to nanoscale dimensions owing to their limited volume. Herein, we demonstrate the production of three-dimensional (3D) pixels with nanoscale dimensions based on the 3D printing of quantum dots embedded in polymer nanowires. In particular, a femtoliter meniscus was used to guide the solidification of liquid inks to form vertically freestanding nanopillar structures. Based on the 3D layout, we show high-density integration of color pixels, with a lateral dimension of 620 nm and a pitch of 3 μm for each of the red, green, and blue colors. The 3D structure enabled a 2-fold increase in brightness without significant effects on the spatial resolution of the pixels. In addition, we demonstrate individual control of the brightness based on a simple adjustment of the height of the 3D pixels. This method can be used to achieve super-high-resolution display devices and various photonic applications across a range of disciplines.

ACS Nano 14, 10993 (2020)

3D integration of photonic nanowire waveguides is demonstrated by a precise and versatile meniscus-guided 3D nanoprinting method. By realizing 3D direct linking of nanophotonic elements with no substrate leakage and, moreover, excellent stretchable operations (>50%), 3D functional photonic components of multiplexers and splitters are demonstrated finally.

Advanced Optical Materials 4, 1190 (2016)