Hydrochromic materials find great utility in a wide range of applications including humidity sensing and measuring the water contents of organic solvents, as well as substrates for rewritable paper and human sweat pore mapping. Herein, an inkjet printable diacetylene (DA) is described that can be transformed by UV irradiation to a hydrochromic‐conjugated polymer on conventional paper. Specifically, an amphiphilic DA that contains an imidazolium ion head‐group is found to be compatible with a common office inkjet printer. Various computer‐designed images are printed on paper using this substance. UV irradiation of the printed images results in the generation of blue‐colored images associated with formation of a polydiacetylene (PDA). The resolutions of the images are almost identical to those generated using a conventional black ink. Importantly, the printed images undergo a blue‐to‐red color change upon exposure to water and the hydrochromism is found to be temperature dependent. The facile color change that occurs near body temperatures enables use of the hydrochromic PDA‐coated paper for rapid and precise mapping of human sweat pores from fingers, palms, and feet.
1wileyonlinelibrary.com creation of electronic based communication methods that substitute for paper has not been as rapid as was expected, which is evidenced by threefold increase in the global consumption of paper over the past few decades. [1,2] According to findings made in recent surveys, most documents containing information recorded on paper are disposed after a one-time use. This trend is creating serious and growing environmental problems associated with deforestation, solid waste, and chemical pollution in air, water, and on land. [3,4] As a result, much attention has been given to the development of rewritable paper that can be used multiple times. If successful, the new technology would help bring about a balance between the socioeconomic advancement of society and environmental protection. In this context, several types of rewritable papers and erasable inks have been described recently. One elegant approach to this problem utilizes a rewritable composite paper, containing a photocatalyzed, color switchable redox dye. In this system, ink-free replication of a text/pattern created by using a preprinted photomask is possible. [5] In another remarkable effort, a hydrochromic dye embedded paper was designed for water-jet printing where water serves as the trigger for color switching. [6] By taking advantage of their tunable refractive index property, photonic crystals have been utilized to fabricate rewritable paper. In this system, a well-ordered photonic coating is embedded on substrate for pattern-on-demand printing using water, [7] hygroscopic salts, [8] and silicon fluid [9] as inks. Furthermore, a wide range of photoresponsive color switchable functionalized azobenzenes, [10,11] flugides, [12,13] bisthienylethenes, [14] spironapthooxazine, [15] and spiropyrans [16] have been explored in potential rewritable paper applications. In similar approaches, phenomenon involving reversible halochromism of oxazine derivatives [17] and thermochromism of leuco dyes [18,19] has been employed to develop rewritable paper systems.In the investigation described below, we devised and tested a new strategy for the design of light-responsive ink for rewritable paper, which is based on the photochromic switching properties of diarylethenes (DEs). DEs are known to undergo light-stimulated (UV-vis) reversible photochemical cyclization and cycloreversion reactions, which are accompanied by color switching from colored closed to colorless open ring forms. Full Color Light Responsive Diarylethene Inks for Reusable PaperWoomin Jeong, Mohammed Iqbal Khazi, Dong-Hoon Park, Young-Sik Jung, and Jong-Man Kim* "Digitalization" represents one approach to shift society's dependence on paper-based communication. However, thus far, this tactic has not had a significant impact on global paper consumption, which has risen over the past few decades. The escalating demand of paper making and consumption has resulted in an intensified negative effect on the environment. Because of this, the development of rewritable paper or erasable ink a...
Owing to a unique colorimetric (typically blue-to-red) feature upon environmental stimulation, polydiacetylenes (PDAs) have been actively employed in chemosensor systems. We developed a highly accurate and simple volatile organic compound (VOC) sensor system that can be operated using a conventional smartphone. The procedure begins with forming an array of four different PDAs on conventional paper using inkjet printing of four corresponding diacetylenes followed by photopolymerization. A database of color changes (i.e., red and hue values) is then constructed on the basis of different solvatochromic responses of the 4 PDAs to 11 organic solvents. Exposure of the PDA array to an unknown solvent promotes color changes, which are imaged using a smartphone camera and analyzed using the app. A comparison of the color changes to the database promoted by the 11 solvents enables the smartphone app to identify the unknown solvent with 100% accuracy. Additionally, it was demonstrated that the PDA array sensor was sufficiently sensitive to accurately detect the 11 VOC gases.
Doppler ultrasonography does not represent the HVPG, and is therefore not suitable for replacing HVPG as a means of assessing the severity of portal hypertension and the response to drugs which reduce the portal pressure in liver cirrhosis.
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