Scientists used printable paints that emit circularly polarized luminescence to produce a flexible display that offers stereoscopic 3D imaging. [Image: M. Zhang et al., Sci. Adv. 9, eadi9944 (2023); CC-BY-NC 4.0]
Researchers in China have reportedly demonstrated a novel photonic paint that can be printed onto fabrics and other textile substrates to achieve 3D stereoscopic imaging (Sci. Adv., doi: 10.1126/sciadv.adi9944). The printable materials were specifically formulated to emit circularly polarized luminescence (CPL), which is known to be particularly beneficial for imaging and display applications, while the scalable fabrication process could help to drive innovation in wearable and smart electronic technologies.
Chiral liquid-crystal microspheres
The photonic paints produced by the researchers harness the unusual optical characteristics of chiral liquid crystals, which are already used in rigid display panels to provide high-contrast pictures with a wide viewing angle. However, the mobile nature of these materials requires them to be confined within a cell structure, which prevents their use in flexible displays.
In the new work, scientists at the University of Science and Technology of China have devised a novel chemical process to encapsulate chiral liquid crystals inside a polymer shell. Liquid crystals are first mixed with fluorescent dyes and emulsified with two natural polymers, which on cooling become crosslinked into a network structure that forms a firm outer layer. The resulting core–shell microspheres produce intense CPL emission when irradiated with ultraviolet light, and they can be formulated into red, green and blue photonic paints that produce either left- or right-handed CPL.
CPL on textiles
The researchers used the paints to write customized graphics on a range of textile substrates, including polypropylene and cotton and polyester fabrics. They also created meter-scale luminous textiles by spray printing the paints onto a stretchy polyester material, achieving uniform light emission with strong circular polarization characteristics.
The researchers used the paints to write customized graphics on a range of textile substrates, including polypropylene and cotton and polyester fabrics.
In addition, the team made flexible display panels by printing two groups of full-color pixel arrays onto a polyester fabric. The two distinct pixel arrays deliver orthogonal CPL emission—one left-handed and the other right-handed—which creates an immersive 3D sensation by presenting the eyes with two adjacent images that have opposite polarization states.
To show the potential of the technology for wearable electronics, the team created a soft, watch-like wristband that can be programmed to display information such as the time and arbitrary text. They also presented a conceptual design for wearable textile devices that have the potential to display stereoscopic information dynamically and enable intelligent applications such as 3D addressing and navigation.