Soft materials and flexible structures for display technologies

http://dx.doi.org/10.1016/j.displa.2016.11.004 0141-9382/ 2016 Published by Elsevier B.V. Curved, bendable, rollable, foldable, conformable, and stretchable displays have fascinated people in recent years. However, to commercialize these novel display devices and systems, not only fundamental developments on materials are required but also advancements on manufacturing techniques are necessary. This special issue includes articles that disclose solutions of substrate manufacturing, functional and active layer enhancement, operation mechanism, and production procedure. A substrate manufacturing idea was proposed by Dr. Miko Cakmak [1] in the first article, in which conductive nanofibers were embedded in polymeric materials in a continuous roll-to-roll film casting line. Although the conductive nanofibers used in this work was composed of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate and poly(ethylene oxide), other solution-based conductive materials could also be applicable in the developed electrospinning process. The demonstrated conductive substrate was with high transmittance in the visible region and was proved elastic by cyclic electrical tests. In addition to the conductive film, conductive stripes were also made by laser ablation for the application of polymer dispersed liquid crystal displays. The second article in this special issue prepared by Dr. Chih-Yu Chao [2] disclosed a simple and efficient method to facilitate the switching speed of twisted nematic liquid crystal at low operation voltage by doping a small amount of n-alcohols. The driving voltage of the enhanced liquid crystal was suppressed by up to 27% and the switching speed was shortened by 20%, making the liquid crystal display practical and energy-efficient in portable applications. Another article prepared by Dr. Dashan Qin [3] disclosed two p-doped hole transport layers for organic light emitting diodes with enhanced device performance with lowered hole transport barriers. These hole transport layers could be manufactured in a cost-efficient way and could be helpful on facilitating the expansion of organic light emitting diodes in the display market. Besides conventional plasmonic displays, Dr. Kazuhiro Takahashi [4] realized an elastic system, in which polymeric material enclosed periodical metallic structures or gratings for surface plasmonic modulations. By straining the polymeric material, metallic structures deformed into other periods and represented alternated colors. The spectrum of this color sheet was retraceable between 400 nm and 700 nm, supporting various applications such as decoration and stress detection. The article that characterizes transparent conductive oxide on plastic substrate in a non-contact way by Dr. Bor-Jiunn Wen [5] is the last one of this special issue. The transmitted electric field of the terahertz time domain spectroscopy varied with changed electrical properties of the transparent conductive oxide, realizing non-contact detection on an invisible film. The studies were compared to the connected detection and the 20,000-time cyclic tests not only summarized the frequency-dependent amplitudes but also concluded the resistivity of the film. This methodology is an effective and efficient detection in the roll-to-roll manufacturing systems. As expected by many researchers, I believe that flexible electronics and displays composed of soft materials would finally come to the market. With the progresses from related researches, we could aggressively expect the realization of these devices and systems that only appeared in movies, novels, and dreams before. The articles collected in this special issue not only disclosed solutions but also inspired people to explore potential possibilities.