Water as a colorful ink: transparent, rewritable photonic coatings based on colloidal crystals embedded in chitosan hydrogel

Paper has remained the world's most-widely accessible information medium even as sustainable and reusable paper replacements have attracted increasing attention. Here, an ink-free rewritable paper concept is developed that combines recent developments in photonic crystals, shape memory polymers, and electroactive polymers in a nanocomposite that matches the benefits of paper as a zero-energy, long-term data storage medium, but provides the additional advantage of rewritability. The rewritable paper consists of a ferroferric oxide-carbon (Fe 3 O 4 @C) core-shell nanoparticle (NP)-based photonic crystal embedded in a bistable electroactive polymer (BSEP). Electrical actuation induces large deformation in the z-axis of the nanocomposite, creating distinct color change in the actuated area. This nanocomposite stores high fidelity color images without inks, the images remain stable after more than a year of storage in ambient conditions, and the stored images can then be rewritten over 500 times without degrading. A seven-segment numerical display is also demonstrated.

Section: Introductionmentioning

confidence: 99%

Bistable and Reconfigurable Photonic Crystals—Electroactive Shape Memory Polymer Nanocomposite for Ink‐Free Rewritable Paper

Xie

Meng

Wang

et al. 2018

“…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, hygroscopic salts, and silicon fluid as inks. Furthermore, a wide range of photoresponsive color switchable functionalized azobenzenes, flugides, bisthienylethenes, spironapthooxazine, and spiropyrans have been explored in potential rewritable paper applications.…”

Section: Introductionmentioning

confidence: 99%

Full Color Light Responsive Diarylethene Inks for Reusable Paper

Jeong

Khazi

Park

et al. 2016

120

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...

“…Another interesting approach to the development water as an ink utilizes colloidal photonic crystals that are constructed from periodically assembled nanoparticles. [ 23 ] Due to their unique band-gap properties, photonic crystals effi ciently refl ect light in specifi c spectral ranges that depend on lattice spacing and particle size. Thus, photonic crystals embedded on hydrogels or polymer matrices have lattice structures that can be tuned by absorption of water.…”

mentioning

confidence: 99%

Inkjet‐Printable Amphiphilic Polydiacetylene Precursor for Hydrochromic Imaging on Paper

Park

Jeong

Seo

et al. 2015

122

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.