Sustainable Rewritable Paper Enabled by Colored Aqueous Inks for Writing, Painting, and Printing Applications

A novel inkjet printing procedure based on a well-dispersed aqueous Ag ink and a molecular adhesive layer is presented for the fabrication of highly conductive and narrow patterns exhibiting the excellent adhesion property on a glass substrate. The aqueous dispersion of silver nanoparticles is synthesized via a chemical reduction method in the aqueous medium in which an anionic polyelectrolyte is incorporated as both a capping agent and a dispersant. Owing to the electrosteric repulsion characteristic of the anionic polyelectrolyte, the prepared aqueous Ag ink exhibits the long-term dispersion stability. A molecular adhesive layer is deposited on a glass substrate using either aminopropyltriethoxysilane or mercaptopropyltriethoxysilane. The distinctive functional group of the molecular adhesive layer plays a critical role in the adhesion property as well as high contact angle appropriate for forming the narrow Ag patterns, which is achieved only with the aqueous ink. It is demonstrated that the resulting inkjet-printed Ag patterns with a line width of 45 μm exhibit the excellent adhesion property and resistivity as low as 3.7 μΩ·cm, after annealing at temperatures ranging from 200 to 300 °C.

As sustainable and eco-friendly replacements to conventional paper, rewritable paper is a very attractive alternative for communication, information circulation, and storage. Development is made for rewritable paper using chromogenic materials that change its color in presence of external stimuli. However, the new techniques have faced several major challenges including feasible operational method, eco-friendly approach. Herein, a simple, convenient, and eco-friendly strategy is described for the preparation of rewritable paper substrate, and multi colored ink for efficient use in writing, painting or printing purpose. In addition, writing with "invisible ink" on the rewritable paper can be realized for potential anti-counterfeiting application. The written, painted, or printed information on the paper substrate can be easily erased using an aqueous solution. Thus, the original paper can be retrieved and the paper substrate can be reused multiple times. Besides, the written or printed information can be retained for a prolonged time at ambient conditions. Overall, this approach shows the rewritable paper as a prototype of multicolor writing/painting application, offering a sustainable solution for reducing paper waste and promoting environmental stewardship.

IR-sintering efficiency on inkjet-printed conductive structures on paper substrates

Rewritable Paper In article number 2403512, Nikita Das and Chandan Maity describe a biopolymer-based aqueous multicolor ink for writing, painting, and printing on a rewritable paper substrate. Written, painted or printed information can be kept for longer time without any visual deformation. The information of the paper can be erased using an aqueous EDTA solution to obtain the original paper, which can be reused multiple times following “write-erase” cycle.

Microstructures Prepared via Inkjet Printing and Embossing Techniques

Recycling of steelmaking electric arc furnace dust into aqueous cyan ceramic ink for inkjet printing process and its printability

Stimuli‐responsive luminescent material‐based rewritable paper has received great attention for its potential application in a wide range of areas from anti‐counterfeiting to information encryption. Herein, a photoluminescence (PL) rewritable paper based on an organic metal halide, trans ‐2,5‐dimethylpiperazine manganese(II) bromide (C 6 N 2 H 16 MnBr 4 ) (1), is reported. This 0D organic metal halide hybrid exhibits green emission centered at 548 nm originating from 4 T 1 – 6 A 1 transition of tetrahedrally coordinated Mn 2+ ions with a PL quantum efficiency of 82%. Interestingly, complex 1 can be transformed into the non‐emissive hydrated phase C 6 N 2 H 16 MnBr 4 (H 2 O) 2 (2) by uptake of coordinating water molecules, wherein Mn 2+ adopts a quasi‐octahedral coordination sphere. The reversible single‐crystal structure transformation between the hydrated and dehydrated phases can switch the PL on and off. Rewritable PL paper has been fabricated by coating complex 1 on filter paper, which exhibits high resolution and excellent “write‐erase‐write” cycle capability. This work presents a new avenue for low‐dimensional lead‐free organic metal halide hybrids toward multilevel information security applications.

Drying-free inkjet printing of cotton fabrics through controlling the diffusion of dye inks in wet sodium alginate films.

A novel inkjet-printed electromagnetic bandgapbacked (EBG) RFID tag has been designed and tested for wearable and metal mount applications. An array of split-ring resonators and a dipole antenna matched to an RFID chip at 915 MHz were designed and inkjet printed on paper substrate. Measurements of the tag in free space show that the required reader's minimum transmit power for successful tag reading decreases by 6 dB compared to the case without EBG, while for on-body and on-metal measurements, the read range increases by nearly a factor of 2. It has to be noted that the proposed RFID tag is flexible since it can be easily fabricated by inkjet printing nano- silver particles on paper or platic substrates. It can find numerous applications ranging from wearable antennas and bio-monitoring to transportation and logiitics for mass shipping.

In this article, the inkjet printing technique is demonstrated for the stacking of reduced graphene oxide (RGO) and molybdenum trioxide (MoO3) nanosheets for flexible all-solid-state micro-supercapacitors. The ammonium molybdate tetrahydrate/graphene oxide ((NH4)6Mo7O24·4H2O/GO) aqueous inks are facilely printed on polymide (PI) film and transformed to RGO/MoO3 hybrids via thermal treatments at air atmosphere. The compound inks are water-based, inkjet-printable, and nontoxic for inkjet printing to form two-dimensional crystal materials. The physical properties of aqueous inks are optimized within a printable range characterized by the Ohnesorge number of 1 < Z < 14. The inkjet-printed symmetric micro-supercapacitors (MSCs) with poly(vinyl alcohol) (PVA)-H2SO4 gel electrolyte possess a wide voltage window of 0-0.8 V, excellent flexibility, a high volumetric specific capacitance of 22.5 F cm-3 at 0.044 A cm-3, as well as good cyclic stability due to the synergistic effect of RGO and MoO3. Furthermore, the inkjet-printed composite MSCs delivered a maximum energy density of 2 mWh cm-3 and a power density of 0.018 W cm-3, and the capacity retention rate of inkjet-printed MSCs is still retained 82% even after 10 000 charge-discharge cycles, indicating good electrochemical properties. Above all, the as-designed inkjet printing technique shows potential for flexible and wearable energy storage electronics.

Inkjet-printed perovskite quantum dot (PQD) color conversion films (CCFs) have great potentials for mini/micro-LED displays because of their ultrahigh color purity, tunable emissions, high efficiency, and high-resolution. However, current PQD inks mainly use expensive, toxic, and flammable organic substances as solvents. In this work, water is proposed to be used as the solvent for inkjet printing PQD/polymer CCFs. The green-emitting patterned MAPbBr3 /polyvinyl alcohol (PVA) films are in situ prepared by using halides and the PVA-based aqueous ink. The as-printed CCFs exhibit a high-resolution dot matrix of 90 µm with a bright green emission (λem = 526nm), a high photoluminescence quantum yield of 85%, and a narrow full width at half maximum of 22nm. They have both air- and photo-stabilities under ambient conditions, and each pixel of CCFs is relatively uniform in morphology and fluorescence when the substrate temperature is 80°C. The patterned blue-emitting MAPbClx Br3-x /PVA and red-emitting Cs0.3 MA0.7 PbBrx I3-x /PVA can also be printed by aqueous inks. These results indicate that the designed aqueous inks are promising for in situ inkjet printing high resolution and reliability PQD CCFs for mini/micro-LED displays.

The advantage of ceramic ink-jet printing technology is the accurate and fast printing process of digital images for various products. For digital ink-jet printing applications, ceramic ink requires proper viscosity and surface tension, along with dispersion stability of the inorganic pigments. The purpose of this study is the formulation of an environment-friendly ceramic ink with a water-based system; using nano-sized CoAl2O4 pigment as a raw material, ink should have dispersion stability to prevent nozzle clogging during ink-jet printing process. In addition, the surface tension of the ceramic ink was optimized with the polysiloxane surfactant according to the surface tension requirement (20 - 45 mN/m) for ceramic ink-jet printing; by adjusting the viscosity with poly ethylene oxide, jetting behavior of the ceramic ink was investigated according to changes in the physical features through drop watcher measurement. Key words: Suspensions, Traditional ceramics, Ink-jet printing, Raw material, Aqueous ceramic ink

Among the various anti‐counterfeiting solutions, fluorescent compounds gained attention as challenging to copy solutions because of astute technological improvements. However, fluorescent compound usage in counterfeit detection is limited due to high price of rare earth metals, the low photostability of pigments or organic dyes, and the long‐term toxicity of conventional semiconductor quantum dots. Herein lies the value of carbon dot, a very stable, reasonably priced, and environmentally friendly material with intriguing features. In this work the development of blue fluorescent, N‐doped carbon dots (NCD) from waste bamboo stem cuttings via hydrothermal route is presented as an environmentally friendly approach to reduce the risk of toxic gas evolution from burning of bamboo waste. The carbon dot's practical application in anti‐counterfeit printing was ascertained by comprehending it's superior properties, such as high water solubility, eco‐friendliness, dazzling fluorescence, and surface functionalization through various characterization techniques. Inkjet printing of the designs on paper substrate using the aqueous NCD ink displayed reversible encryption‐decryption ability through variation of pH. The development paves the way for value‐added utilization of waste bamboo cuttings in fluorescent ink production.

Direct printing of functional inks onto flexible substrates allows for scalable fabrication of wearable electronics. However, existing ink formulations for inkjet printing require toxic solvents and additives, which make device fabrication more complex, limit substrate compatibility, and hinder device performance. Even water‐based carbon or metal nanoparticle inks require supplemental surfactants, binders, and cosolvents to produce jettable colloidal suspensions. Here, a general approach is demonstrated for formulating conductive inkjet printable, additive‐free aqueous Ti3C2Tx MXene inks for direct printing on various substrates. The rheological properties of the MXene inks are tuned by controlling the Ti3C2Tx flake size and concentration. Ti3C2Tx‐based electrical conduits and microsupercapacitors (MSCs) are printed on textile and paper substrates by optimizing the nozzle geometry for high‐resolution inkjet printing. The chemical stability and electrical properties of the printed devices are also studied after storing the devices for six months under ambient conditions. Current collector‐free, textile‐based MSCs show areal capacitance values up to 294 mF cm−2 (2 mV s−1) in poly(vinyl alcohol)/sulfuric acid gel electrolyte, surpassing reported printed MXene‐based MSCs and inkjet‐printed MSCs using other 2D nanomaterials. This work is an important step toward increasing the functional capacity of conductive inks and simplifying the fabrication of wearable textile‐based electronics.

The objective of this study is to demonstrate ultra-low-cost paper substrates for the realization of inexpensive RFID tags that can be integrated with batteries and sensors for wireless sensing, tracking and monitoring applications. The first step toward achieving this goal is to demonstrate "conductors on paper substrates" from processing standpoint and to characterize the electrical performance of paper substrates up to 2 GHz form design standpoint. The conductors are achieved by (i) direct-write ink jet printing technology with tailored conductive ink and by (ii) conventional copper etching upon lamination of metal foils on to the paper substrates. There are several issues in optimizing the processes in either of the two approaches. For example, ink jet printing would require smooth surface finish, good adhesion, less smearing of the ink, fast curing profile, and ultimately copper-like conductivity of the printed ink and rapid prototyping for high volume manufacturing. On the other hand, metallization using copper will require bonding of copper onto paper surface, adhesion, compatibility with copper etch solutions and lithography, and moisture sealing. Both approaches have been successfully demonstrated for printing conductors on paper substrates which can be easily scaled to large-quantity manufacturing. For the electrical characterization of the paper substrates up to 2 GHz, one microstrip ring resonator was designed and fabricated for extracting dielectric constant and dielectric losses. The copper metallization of paper substrates and the dielectric characterization of paper up to 2 GHz are reported for the first time.