Ink Solution Research Articles

Boron nitride nanotubes reinforced gelatin hydrogel-based ink for bioprinting and tissue engineering applications.

The rapid evolution of 3D bioprinting technique, very few biomaterials have been studied and utilised as ink solutions to produce structures. In this work, a polymeric nanocomposite hydrogel-based ink solution was developed using boron nitride nanotubes (BNNTs) reinforced gelatin for 3D bioprinting of scaffolds. The ink solutions and printed scaffolds were characterised for their printability, mechanical, thermal, water uptake, and biological properties (cell viability and inflammation). The viscoelastic behaviour of the scaffolds indicated the increase in storage modulus with an increase in BNNTs composition. Additionally, the compressive strength of the scaffolds increased from 9.43±1.3kPa to 30.09±1.5kPa with the addition of BNNTs. Similarly, the thermal stability of the scaffolds enhanced with an increase in BNNTs composition. Furthermore, the scaffolds with a higher concentration of BNNTs displayed resilience in cell culture media at 37°C for up to 14days compared with pure gelatin scaffolds. The cell viability results showed a decreased viability rate with an increased concentration of BNNTs scaffolds. However, BNNTs incubated with cells did not display cytokine inflammation. Therefore, this work provides a potential hydrogel-based ink solution for 3D bioprinting of biomimetic tissue constructs with adequate structural stability for a wide range of tissue engineering and regenerative medicine applications.

Controllable depositing behaviors and deposited morphologies of inkjet droplets on high energy surface

The high energy surface (HES) could realize a super-spreading process for droplet. In this work, a facile method was applied to fabricate HES by hydrothermally treating aluminum foil. The inkjet ink is obtained by dissolving poly acrylic acid (PAA) in ethanol. The depositing behaviors of inkjet droplet was investigated and controlled with pinned three phase contact lines. And the influence of coffee ring effect on the depositing behavior of inkjet droplet could be regulated to generate a variety of deposited morphologies, including super-spreading structure, ring structure, and homogeneous structure. With the inkjet printed pattern of PAA solution ink on the HES, a patterned wettability surface with high energy area and low energy area could be fabricated by modifying the surface with fluoro-alkyl silanes and removing the inkjet printed PAA with deionized water, which could transport water from bottom to up with a high wettability contrast. This work presented a systematic study in controllable depositing behaviors and deposited morphologies of the inkjet droplets on high energy surface. It has a great potential for the development of material patterning, 3D printing as well as related interface researching.

3D Printing of Largescale Functional Nanofilm using Electrically assisted Direct Ink Deposition

Functional nanofilms show significant importance for various applications in different fields, such as sustainable energy, biomedicine, electronics, and optics. However, there are still many challenges in the fabrication of nanostructured films with tailored properties using traditional manufacturing technologies. A novel 3D printing approach called electrical field-assisted direct ink deposition (EF-DID) was developed to produce large-scale nanofilms with controllable nanostructures and patternable features. In the proposed method, the formation of nanodroplets in the direct ink deposition was investigated under an electrostatic field with high voltage. Critical printing parameters, including solution concentration, deposition height, applied voltage, and ink flow rate, were studied systematically to understand fundamental mechanisms of the nanostructures generation during the printing. In addition, the scientific relationship between deposition parameters and nanofilm properties, including film thickness, electrical conductivity, and contact angle, were explored. Finally, patterned nanofilms with well-organized nanostructures were fabricated to demonstrate potential application prospects in the field of nanotechnology.

Quantum Dot-based Luminescent Solar Concentrators Fabricated through the Ultrasonic Spray-Coating Method.

Luminescent solar concentrators (LSCs) are a class of wave-guiding devices that can harvest solar light and concentrate it to targeted smaller areas. When coupled with photovoltaic devices (PVs), LSCs hold the potential to be integrated into various application setups, especially for building facade integration toward net-zero-energy buildings. Developing reliable LSC fabrication methods with easy scalability, high adaptability, and device controllability has been an important research topic. In this work, we report an ultrasonic nebulization-assisted spray deposition technique to fabricate quantum dot (QD)-based LSCs (QD-LSCs). This method allows for the production of high-performance QD-LSCs with different device dimensions and geometries. In addition, the quality of the QD thin-film coating layer is relatively independent of the concentration and volume of the coating QD ink solution, allowing for deliberate programming and performance optimization of the resulting QD-LSC devices. We anticipate that this ultrasonic spray coating method can be widely applied to the manufacturing of high-quality LSC devices that are integrable to various applications.

Exploring Nanoscale Structure in Perovskite Precursor Solutions Using Neutron and Light Scattering

Tailoring the solution chemistry of metal halide perovskites requires a detailed understanding of precursor aggregation and coordination. In this work, we use various scattering techniques, including dynamic light scattering (DLS), small angle neutron scattering (SANS), and spin–echo SANS (SESANS) to probe the nanostructures from 1 nm to 10 μm within two different lead-halide perovskite solution inks (MAPbI3 and a triple-cation mixed-halide perovskite). We find that DLS can misrepresent the size distribution of the colloidal dispersion and use SANS/SESANS to confirm that these perovskite solutions are mostly comprised of 1–2 nm-sized particles. We further conclude that if there are larger colloids present, their concentration must be <0.005% of the total dispersion volume. With SANS, we apply a simple fitting model for two component microemulsions (Teubner–Strey), demonstrating this as a potential method to investigate the structure, chemical composition, and colloidal stability of perovskite solutions, and we here show that MAPbI3 solutions age more drastically than triple cation solutions.

Solution-Processed SnO2 Quantum Dots for the Electron Transport Layer of Flexible and Printed Perovskite Solar Cells.

Flexible and printed perovskite solar cells (PSCs) fabricated on lightweight plastic substrates have many excellent potential applications in emerging new technologies including wearable and portable electronics, the internet of things, smart buildings, etc. To fabricate flexible and printed PSCs, all of the functional layers of devices should be processed at low temperatures. Tin oxide is one of the best metal oxide materials to employ as the electron transport layer (ETL) in PSCs. Herein, the synthesis and application of SnO2 quantum dots (QDs) to prepare the ETL of flexible and printed PSCs are demonstrated. SnO2 QDs are synthesized via a solvothermal method and processed to obtain aqueous and printable ETL ink solutions with different QD concentrations. PSCs are fabricated using a slot-die coating method on flexible plastic substrates. The solar cell performance and spectral response of the obtained devices are characterized using a solar simulator and an external quantum efficiency measurement system. The ETLs prepared using 2 wt% SnO2 QD inks are found to produce devices with a high average power conversion efficiency (PCE) along with a 10% PCE for a champion device. The results obtained in this work provide the research community with a method to prepare fully solution-processed SnO2 QD-based inks that are suitable for the deposition of SnO2 ETLs for flexible and printed PSCs.

Printability of Double Network Alginate-Based Hydrogel for 3D Bio-Printed Complex Structures.

Three-dimensional (3D) bio-printing has recently emerged as a crucial technology in tissue engineering, yet there are still challenges in selecting materials to obtain good print quality. Therefore, it is essential to study the influence of the chosen material (i.e., bio-ink) and the printing parameters on the final result. The “printability” of a bio-ink indicates its suitability for bio-printing. Hydrogels are a great choice because of their biocompatibility, but their printability is crucial for exploiting their properties and ensuring high printing accuracy. However, the printing settings are seldom addressed when printing hydrogels. In this context, this study explored the printability of double network (DN) hydrogels, from printing lines (1D structures) to lattices (2D structures) and 3D tubular structures, with a focus on printing accuracy. The DN hydrogel has two entangled cross-linked networks and a balanced mechanical performance combining high strength, toughness, and biocompatibility. The combination of poly (ethylene glycol)-diacrylate (PEDGA) and sodium alginate (SA) enables the qualities mentioned earlier to be met, as well as the use of UV to prevent filament collapse under gravity. Critical correlations between the printability and settings, such as velocity and viscosity of the ink, were identified. PEGDA/alginate-based double network hydrogels were explored and prepared, and printing conditions were improved to achieve 3D complex architectures, such as tubular structures. The DN solution ink was found to be unsuitable for extrudability; hence, glycerol was added to enhance the process. Different glycerol concentrations and flow rates were investigated. The solution containing 25% glycerol and a flow rate of 2 mm/s yielded the best printing accuracy. Thanks to these parameters, a line width of 1 mm and an angle printing inaccuracy of less than 1° were achieved, indicating good shape accuracy. Once the optimal parameters were identified, a tubular structure was achieved with a high printing accuracy. This study demonstrated a 3D printing hydrogel structure using a commercial 3D bio-printer (REGEMAT 3D BIO V1) by synchronizing all parameters, serving as a reference for future more complex 3D structures.

(Invited, Digital Presentation) Chemical Insights into Perovskite Ink Stability

Metal halide perovskite (MHP) semiconductors are excellent candidates for contemporary optoelectronics innovation, particularly for photovoltaics.1 The advantages of this class of materials derive from their hybrid nature, allowing for straightforward fabrication processes, and from their unique optoelectronic properties.A typical 3D organic-inorganic perovskite has a chemical formula of ABX3, where A is an organic cation (such as MA [methylammonium] or FA [formamidinium]), B is a metal cation (such as Pb2+), and X is a halogen anion (such as I or Br).2 However, recent advances have also explored more complex compositions embedding diverse cations/anions.3 These materials are prepared by simple and straightforward solution processing, the material precursors dissolved in a solvent undergoes self-assembly into a perovskite structure during spin-coating onto a substrate under mild thermal annealing.As the technology continues to mature, this still is a key advantage, allowing for affordable and scalable processing. Understanding perovskite ink properties is therefore a fundamental requirement towards industrialization, with special regards to their evolution over time.It has been demonstrated that even for the simplest system, the precursor solution is a complex – and dynamic – dispersion which contains not only solvated ions but also lead halide complexes, colloids and aggregates of different natures and dimensions. In these complex dispersions, multiple chemical species are present and can interact – or react – between each other or with the solvent.We have proved the existence of a reactivity between two of the perovskite components – methylammonium and formamidinium – in the precursors solutions, that leads to ink variations over time, which in turn means variation in the final polycrystalline material properties. In fact, the characteristics of precursor solution eventually dictate the optoelectronic quality of resulting perovskite films that proceed with the solution aging and determine undesirable decrease of solar cells performances. We have studied different parameters that affects such reactions kinetics and proposed solutions to overcome these issues.4 Starting from the known reactivity of the chemical species present in ink solutions, we outline the directions towards which future research efforts should be directed.5

Droplets transport together with a small steel ball driven by surface acoustic waves

A new method for transporting microfluid was presented. An interdigital transducer was fabricated on an YX-128° LiNbO3 piezoelectric substrate for generating surface acoustic wave (SAW). A sample droplet is placed on a small steel ball, which is driven by the SAW. Temperature characteristics of the sample droplet are theoretically analyzed, and experimentally verified. Red ink solution is demonstrated for sample droplet transport. The presented transport method is successfully applied in color development reaction. Compared to traditional SAW driving droplets, the equilibrium temperature of sample droplet driven by presented method is decreased 11.8 °C at 30.9 dBm of electrical signal power.

Piezoelectric inkjet printing of tyrosinase (polyphenol oxidase) enzyme on atmospheric plasma treated polyamide fabric

Tyrosinase enzyme was digitally printed on plasma pretreated polyamide-6,6 fabric using several sustainable technologies. Ink containing carboxymethyl cellulose was found to be the most suitable viscosity modifier for this enzyme. Before and after being deposited on the fabric surface, the printed inks retained enzyme activity of 69% and 60%, respectively, compared to activity prior printing process. A good number of the printed enzyme was found to be strongly adsorbed on the fabric surface even after several rinsing cycles due to surface activation by plasma treatment. Rinsed out fabrics retained a maximum activity of 34% resulting from the well-adsorbed enzymes. The activity of tyrosinase on printed fabrics was more stable than ink solution for at least 60 days. Effects of pH, temperature and enzyme kinetics on ink solution and printed fabrics were assessed. Tyrosinase printed synthetic fabrics can be utilized for a range of applications from biosensing and wastewater treatment to cultural heritage works.

Ink Rheology Regulates Stability of Bioprinted Strands.

Three-dimensional (3D) extrusion bioprinting typically requires an ad hoc trial-and-error optimization of the ink composition toward enhanced resolution. The ink solutions are solidified after leaving cone-shaped or cylindrical nozzles. The presence of ink instability not only hampers the extrusion resolution but also affects the behavior of embedded cellular components. This is a key factor in selecting (bio)inks and bioprinting design parameters for well-established desktop and handheld bioprinters. In this work, we developed an analytical solution for the process of ink deposition and compared its predictions against numerical simulations of the deposition. We estimated the onset of ink instability as a function of ink rheological properties and nozzle geometry. Our analytical results suggest that enhancing the shear-thinning behavior of the ink shortens the toe region of the deposition. Such an extrusion process is often desired, as it leads to faster depositions. However, we demonstrated that such conditions increase the possibility of lateral buckling of the strand once touching the substrate defined as instability in this study. The present study serves as a benchmark for detailed simulations of the extrusion process for optimal bioprinting.

Preparation of photoluminescent nanocomposite ink toward dual-mode secure anti-counterfeiting stamps

Fluorescent photochromism has been applied as an attractive approach for the production of effective authentication substrates to show dual-mode secure encoding. In the current study, novel photochromic and fluorescent nanocomposite ink was developed to introduce a stamped film with strong dual-mode emission for anti-counterfeiting purposes. Inorganic/organic nanocomposite ink was developed from lanthanide-doped aluminate (LDA) dispersed in poly(acrylic acid)-based binder. To produce a transparent film, LDA must be dispersed well in the poly(acrylic acid)-based ink solution. The fluorescent and photochromic nanocomposite ink was stamped effectively onto cellulose documents followed with thermal fixation. Homogeneous fluorescent and photochromic layer was stamped onto paper surface providing a transparent look with the ability to switch to green beneath ultraviolet as illustrated by CIE Lab. The stamped documents were studied by photoluminescence spectra to show an absorption peak at 364 nm, and fluorescence band at 438 nm. The induced security encoding was transparent beneath visible light turning into visible greenish-yellow beneath ultraviolet light indicating a bathochromic shift. LDA was synthesized in the nanoparticle form and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The morphological properties of the stamped documents were examined by infrared spectroscopy (FTIR), scan electron microscope (SEM), EDS, and X-ray fluorescence (XRF). The stamped paper sheets displayed an efficiently reversible photochromism without fatigue under visible and ultraviolet lights. The rheologies of the prepared photoluminescent nanocomposite inks as well as the mechanical performance of the stamped sheets were investigated.

Coupling of Fused Deposition Modeling and Inkjet Printing to Produce Drug Loaded 3D Printed Tablets.

In the current study, we have coupled Fused Deposition Modelling (FDM) for the fabrication of plain polyvinyl alcohol (PVA) tablets followed by dispensing of minoxidil ethanolic solutions using inkjet printing. The use of a drop-on-solid printing approach facilitates an accurate and reproducible process while it controls the deposition of the drug amounts. For the purpose of the study, the effect of the solvent was investigated and minoxidil ink solutions of ethanol 70% v/v (P70) or absolute ethanol (P100) were applied on the plain PVA tablets. Physicochemical characterization showed that solvent miscibility with the polymer substrate plays a key role and can lead to the formation of drug crystals on the surface or drug absorption in the polymer matrix. The produced minoxidil tablets showed sustained release profiles or initial bursts strongly affected by the solvent grade used for dispensing the required dose on drug loaded 3D printed tablets. This paradigm demonstrates that the coupling of FDM and inkjet printing technologies could be used for rapid development of personalized dosage forms.

Improving quality of smoked sardine fillets by soaking in cuttlefish ink

Cuttlefish ink, a by-product of food processing, is a promising source of natural compounds with antioxidant and antimicrobial activities and it can be used as a natural additive for sea food products. Therefore, this work aimed to extend the shelf life of smoked sardine by soaking in cuttlefish ink solution. No antibacterial activity of cuttlefish ink solution with different concentrations (1%, 2% and 3%) has been determined against Staphylococcus aureus, Listeria monocytogenes and Pseudomonas aeruginosa. DPPH radical scavenging activity for the ink samples ranged from 91% to 95% for the three ink solutions. Fresh fillets were steamed, smoked and soaked in the three ink solutions and then stored at 4 °C for 35 days. During storage, total viable counts, total volatile basic nitrogen values and peroxide values increased significantly only for control samples and those soaked with 1% of ink solution. Soaked samples showed the lowest amount of histamine when compared to the control one which may be related to a better controlled microbial proliferation. Ink solutions did not affect the whiteness of fillets, whereas the hardness increased significantly during the two first weeks of storage. Obtained results support using cuttlefish ink to lengthen smoked sardine shelf life.

High electrochemical performance of ink solution based on manganese cobalt sulfide/reduced graphene oxide nano-composites for supercapacitor electrode materials.

Large scale supercapacitor electrodes were prepared by 3D-printing directly on a graphite paper substrate from ink solution containing manganese cobalt sulfide/reduced graphene oxide (MCS/rGO) nanocomposites. The MCS/rGO composite solution was synthesized through the dispersion of MCS NPs and rGO in dimethylformamide (DMF) solvent at room temperature. Their morphology and composition were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray diffraction (EDS). The role of rGO on decreasing charge transfer resistance and enhancing ion exchange was discussed. The MCS/rGO electrode exhibits an excellent specific capacitance of 3812.5 F g−1 at 2 A g−1 and it maintains 1780.8 F g−1 at a high current density of 50 A g−1. The cycling stability of the electrodes reveals capacitance retention of over 92% after 22 000 cycles at 50 A g−1.

Printable gelatin, alginate and boron nitride nanotubes hydrogel-based ink for 3D bioprinting and tissue engineering applications

Hydrogels comprised of alginate and gelatin are potential biomaterials for extrusion-based bioprinting. However, existing polymeric inks are inadequate in printability, shape fidelity and mechanical properties that desire to produce scaffold using 3D bioprinting. Here, a novel printable hydrogel-based ink solution comprised of gelatin-alginate (GA) reinforced by boron nitride nanotubes (BNNTs) was developed for 3D bioprinting and tissue engineering applications. The ink solutions were tested for printability, printing accuracy, compressive behaviour, while the printed scaffolds were tested for their viability of human embryonic kidney cells (HEK293T). Printability tests showed the strand thicknesses decreased with the increasing concentration of BNNTs in the GA ink solutions. Similarly, the printing accuracy increased (>90%) with the increasing loading of BNNTs. However, the swelling rate of the GA scaffold was higher than BNNTs reinforced GA scaffolds. Mechanical properties were measured by using compression testing. Increasing BNNTs concentration in GA resulted in a higher load of compressive stress. Also, a quantitative analysis of the cell viability of scaffolds revealed a slight effect on toxicity with the increased doping of BNNTs. Hence, the relevant data on BNNTs reinforced GA scaffold indicated that it could be a potential ink solution for tissue engineering applications through 3D bioprinting processes.

Inkjet-Printed, Nanofiber-Based Soft Capacitive Pressure Sensors for Tactile Sensing

The development of soft electronics is critical to the realization of artificial intelligence that comes into direct contact with humans, such as wearable devices, and robotics. Furthermore, rapid prototyping and inexpensive processes are essential for the development of these applications. We demonstrate here an additive, low-cost method for fabricating polydimethylsiloxane based soft electronics by inkjet printing. Herein, a novel approach using a water-soluble polyvinyl alcohol layer as the substrate, inexpensive, fully digital fabrication of capacitive pressure sensors is enabled by sandwiching mesh-like conductive layers and microstructured dielectric in a straightforward, convenient manner. These sensors exhibit improved sensitivity (4 MPa^&#x2212;1) at low pressures (&#x003C; 1 kPa) in contrast to sensors with a flat elastomer dielectric and can still detect large pressures around 50 kPa, having excellent long-term repeatability over 2000 cycles, without significant hysteresis (&#x2264; 8.5 &#x0025;). The tactile sensing ability of the fabricated devices was demonstrated in a practical application. Moreover, sensor characteristics are easily adjustable, simply by changing printing parameters or tuning the ink solution. The proposed approach provides scalable solution for fabricating high-sensitivity printed sensors for e-skin and human-machine interfaces.

In-Vitro Investigation of Flow Profiles in Arteries Using the Photoplethysmograph.

The flow profile in the artery reflects the health status of the vessel and generally the arterial system. The aim of this pilot study was to investigate in-vitro the effect of flow profiles on reflective photoplethysmography (PPG) signals at different steady state flow rates and levels of vessel constrictions. A simplified model of an arterial system was built, consisting of a steady state flow gear pump, PVC vinyl tubing, reservoir and a clamp with a micrometer gauge. The blood mimicking fluid (2.5% India ink and water solution) was pumped through the model. It was found that the waveforms of the PPG signals fluctuate irregularly and the magnitude of the frequency components was increased below 60 Hz in cases of turbulent flow (Re = 2503). These preliminary results suggest that PPG could be the basis for new technologies for assessing the profile of the blood flow in the artery. Future studies have to be carried out with pulsatile flow and more complex models that are more similar to the human arterial system.Clinical Relevance- The PPG signal reflects changes in the flow profile caused by the stenotic rigid vessel.

Study on dysprosium iron titration analysis based on chromaticity analysis

In the process of artificial titration of dysprosium iron, it is difficult for human eyes to judge the change of the color of the solution, which will lead to inaccurate titration end point and increased error. In this paper, a color sensor is used to replace human eyes to identify the phenomenon of color mutation in solution, and a variety of filtering methods are used to filter the RGB value of the solution collected by the color sensor. It is found that gaussian filtering and moving average filtering can remove noise very well. At the same time, it is found that the color space conversion can more accurately identify the mutation phenomenon of solution color. Finally, using soy sauce, blue black ink, potassium permanganate and other solutions to simulate the experiment, get better experimental results.

Vasa nervorum of epicardial nerves and valves of small veins investigated in porcine heart by two types of vascular injections.

The morphology of the vascular supply of peripheral branches of cardiac nerves has not been systematically described until now. The aim of this study was to describe the architectonics of the vasa nervorum of epicardial nerves in porcine hearts by using two injection techniques. Twenty-three hearts from young healthy pigs were used. In 10 hearts India ink solution was injected into the origin of the anterior interventricular branch. In another 10 hearts India ink solution was injected retrogradely through the coronary sinus. The hearts were then analyzed using a magnifying glass and light microscopy. The arterial injection showed the entirety of the rich venous components of the vasa nervorum, which often consisted of paired veins accompanying the epicardial nerves. The thickness of the nerves ranged from 50 to 815 μm. The vasa nervorum drained into larger subepicardial veins. In seven of the hearts prepared with venous injections the vasa nervorum of epicardial nerves were visualized in the same detail as in the arterial preparations and India ink solution filled the right ventricle via the smallest cardiac veins. The histological analysis of these seven hearts showed complete dehiscence and functional insufficiency of small and larger veins valves. In the other three hearts prepared with venous injections the valves were competent, which prevented retrograde filling of larger and smaller veins. The results obtained expand the current knowledge on epicardial nerves vasa nervorum and provide anatomical evidence behind the mechanism of retrograde application of cardioplegic solutions in cardiac surgery.