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Flexible and Stretchable Paper-Based Structures for Electronic Applications
Published in Muhammad Mustafa Hussain, Nazek El-Atab, Handbook of Flexible and Stretchable Electronics, 2019
Tongfen Liang, Ramendra Kishor Pal, Xiyue Zou, Anna Root, Aaron D. Mazzeo
Paper-based displays are in the early developing stage. The most common paper-based displays rely on color changes of thermochromic ink upon Joule heating from electrically conductive wires (heaters) patterned on the back of the paper. Such displays normally work with a voltage less than 10 V and take 10–15 s to reach a steady state. Siegel et al. patterned thermochromic ink made of Leuco dye over pre-printed images on a photopaper (Figure 15.16a). Upon heating, the Leuco dye changed from opaque to transparent to reveal the images underneath. Their 100-µm thin display has a minimum resolution of approximately 200 µm × 200 µm. A key advantage of such displays is that they can present predefined complex messages including passages of text in multiple languages or intricate multi-color images (Siegel et al. 2009).
Functional Nanoceramics A Brief Review on Structure Property Evolutions of Advanced Functional Ceramics Processed Using Microwave and Conventional Techniques
Published in Sivashankar Krishnamoorthy, Krzysztof Iniewski, Nanomaterials, 2017
Santiranjan Shannigrahi, Mohit Sharma
Electrochromic materials literally change from transparent to opaque at the flick of a switch. Applying an electrical field to these materials causes a change in the structure and thus a change in color. Photochromic materials change color with a change in the level of UV light and have been widely used as coatings on spectacle lenses. Probably the most well-known color-changing materials are the thermochromic polymers, which change with variations in temperature. There are two types of thermochromic systems: those based on liquid crystals and those that rely on molecular rearrangement. In both cases, a change in the structure of the material occurs at a particular temperature giving rise to an apparent change in color. The change is reversible, so as the material cools down it changes color back to its original state. In liquid crystals, the change from colored to transparent takes place over a small temperature range (around 1°C) and arises as the crystals in the material change their orientation. Thermochromic materials have found a number of applications such as color-changing toothbrushes, baby spoons, which indicate whether food is too hot, and even kettles, which change color as the water is heated. The pigments can be incorporated into dyes for fabric to produce clothing that changes color with variations in temperature. Thermochromic inks can also be used for printing onto clothing and food packaging.
Multi-field driven thermochromic films and preparation of multi-color patterns
Published in Liquid Crystals, 2022
Jiasong Zheng, Zemin He, Chunsheng Li, Zongcheng Miao, Dong Wang, Yi Luan, Yuzhan Li, Yuzhen Zhao
Researchers have done a lot of research on the performance of PDLC, but there are few studies has been done on the driving mode of PDLC. Thermochromic inks have ideal temperature field driving modes and can be a new driving mode for liquid crystal films. Thermochromic ink is a special ink that uses colour change to display the temperature change and temperature distribution on the surface of an object, and can display different colours at different temperatures. Among them, thermochromic liquid crystal relies on the change of optical properties of the material lattice caused by the temperature change to display the colour change [24,25]. Thermochromic liquid crystals are microencapsulated inks in terms of preparation methods. Because liquid crystals are easily contaminated by reactions with other substances, natural polymers are needed to prepare microcapsules to protect liquid crystal microdroplets. The temperature range of thermochromic liquid crystals is generally −20 to 250°C and the sensitivity of colour change can reach 0.1°C [26–28] Roth TB et al [29] systematically measured the colour-changing properties of thermochromic liquid crystals and determined the variation pattern of liquid crystal transmittance versus temperature (27°C-48°C). Zhang WX et al [30] fabricated a temperature-responsive liquid crystal layer with a protective layer by using cholesteric phase liquid crystals. This method is easy to process, and the prepared coating has thermochromic stability and reversibility. A process reference is provided for future applications of thermochromic liquid crystals.