Ink Materials Research Articles

Fluid Bath-Assisted 3D Printing for Biomedical Applications: From Pre- to Postprinting Stages.

Fluid bath-assisted three-dimensional (3D) printing is an innovative 3D printing strategy that extrudes liquid ink materials into a fluid bath to form various 3D configurations. Since the support bath can provide in situ support, extruded filaments are able to freely construct complex 3D structures. Meanwhile, the supporting function of the fluid bath decreases the dependence of the ink material's cross-linkability, thus broadening the material selections for biomedical applications. Fluid bath-assisted 3D printing can be divided into two subcategories: embedded 3D printing and support bath-enabled 3D printing. This review will introduce and discuss three main manufacturing processes, or stages, for these two strategies. The stages that will be discussed include preprinting, printing, and postprinting. In the preprinting stage, representative fluid bath materials are introduced and the bath material preparation methods are also discussed. In addition, the design criteria of fluid bath materials including biocompatibility, rheological properties, physical/chemical stability, hydrophilicity/hydrophobicity, and other properties are proposed in order to guide the selection and design of future fluid bath materials. For the printing stage, some key technical issues discussed in this review include filament formation mechanisms in a fluid bath, effects of nozzle movement on printed structures, and design strategies for printing paths. In the postprinting stage, some commonly used postprinting processes are introduced. Finally, representative biomedical applications of fluid bath-assisted 3D printing, such as standalone organoids/tissues, biomedical microfluidic devices, and wearable and bionic devices, are summarized and presented.

Aqueous high-voltage all 3D-printed micro-supercapacitors with ultrahigh areal capacitance and energy density

With the rapid development of integrated and miniaturized electronics, the planar energy storage devices with high capacitance and energy density are in enormous demand. Hence, the advanced manufacture and fast fabrication of microscale planar energy units are of great significance. Herein, we develop aqueous planar micro-supercapacitors (MSCs) with ultrahigh areal capacitance and energy density via an efficient all-3D-printing strategy, which can directly extrude the active material ink and gel electrolyte onto the substrate to prepare electrochemical energy storage devices. Both the printed active carbon/exfoliated graphene (AC/EG) electrode ink and electrolyte gel are highly processable with outstanding conductivity (~97 S cm−1 of electrode; ~34.8 mS cm−1 of electrolyte), thus benefiting the corresponding shaping and electrochemical performances. Furthermore, the 3D-printed symmetric MSCs can be operated stably at a high voltage up to 2.0 V in water-in-salt gel electrolyte, displaying ultrahigh areal capacitance of 2381 mF cm−2 and exceptional energy density of 331 μWh cm−2, superior to previous printed micro energy units. In addition, we can further tailor the integrated 3D-printed MSCs in parallel and series with various voltage and current outputs, enabling metal-free interconnection. Therefore, our all-3D-printed MSCs place a great potential in developing high-power micro-electronics fabrication and integration.

A Novel Method for Preparation of Carrageenan/Fish Scale Collagen/Allopurinol Biocomposite Film

Biopolymers such as carrageenan or collagen can be used as carriers for loading a drug to enhance a drug’s bioavailability. In this work, allopurinol was loaded on a carrageenan/collagen blend and the carrageenan/collagen/allopurinol (CCA) biocomposite films were prepared using the ionic gelation method combined with the 3D printing method using carrageenan/collagen/allopurinol gel as a 3D printing ink material. The advantages of the 3D printing method are the ease in shaping the design of films and the ease in controlling the thickness of films. The results of infrared (IR) spectroscopy and field emission scanning electron microscopy (FESEM) analyses showed that the CCA biocomposite films have a regular structure, and the functional groups of components in the biocomposites can interact with each other. After 30 minutes of immersion in distilled water and pH buffer solution, the biocomposite films swelled and disintegrated. The carrageenan/collagen blend can control the release of allopurinol in simulated body fluids. In addition, the drug release kinetic models reflecting the release process of allopurinol from CCA biocomposite films in simulated body fluids have also been calculated.

Nanoclay Suspension-Enabled Extrusion Bioprinting of Three-Dimensional Soft Structures

Abstract Three-dimensional (3D) extrusion printing of cellular/acellular structures with biocompatible materials has been widely investigated in recent years. However, the requirement of a suitable solidification rate of printable ink materials constrains the utilization of extrusion-based 3D printing techniques. In this study, the nanoclay yield-stress suspension-enabled extrusion-based 3D printing system has been investigated and demonstrated to overcome solidification rate constraints during printing. Utilizing the liquid–solid transition property of nanoclay suspension, two fabrication approaches, including nanoclay support bath-enabled printing and nanoclay-enabled direct printing, have been proposed. For the former approach, nanoclay (Laponite® EP) has been used as a support bath material to fabricate alginate-based tympanic membrane patches. The constituents of alginate-based ink have been investigated to have the desired mechanical property of alginate-based tympanic membrane patches and facilitate the printing process. For the latter approach, nanoclay (Laponite® XLG) has been used as an internal scaffold material to help print poly (ethylene glycol) diacrylate (PEGDA)-based neural chambers, which can be further cross-linked in air. Mechanical stress analysis has been performed to explore the geometric limitation of printable Laponite® XLG-PEGDA neural chambers.

Modulating Conductivity in Paintable Films from Solvent-Exfoliated Inks of 2D MoS2 and Bi2te3

Research on two-dimensional (2D) layered materials such as graphene,(1) transition metal dichalcogenides (TMDs), carbide and carbonitride relatives called MXenes,(2) has progressed beyond discovery to a wide range of uses. (3,4) In all applications where electronic transport is important, 2D materials, their assemblies, deposition, homo- and hetero-interfaces, layered networks, and composite with polymers, strongly influence the nature of conductivity and consequently the type of electrode or device. Photonics and optoelectronic investigations (5,6) are also sensitive to engineering of 2D materials and their composites, while energy storage and thermoelectric applications using 2D materials must take into account ion accessibility and thermal conductivity, respectively, in addition to electrical conductivity.Exfoliation of parent bulk crystals to give 2D and few-layer MoS2 (7,8) and Bi2Te3 dispersions in solvents may also be promising functional inks. Whether thixotropic or dilatant, inks from particle dispersions are the basis of many printing and coating technologies.(9,10) Incorporating new functionality using 2D materials with standard processing has potential for interesting applications.Here, we developed inks using high concentrations of exfoliated MoS2 and Bi2Te3 2D layer suspensions that can be painted as uniform films on substrates (11,12). Conductivity is controlled at material-level by high quality exfoliated 2D sheets, and in the case of Bi2Te3 we examined the influence of a PEG400 binder additive to the ink. We discuss the nature of in-plane electronic conductivity in painted films from both of these 2D material inks, and summarize measurements that show how conductivity is altered by the painting direction and aspect ratio of coated films. References (1) A. K. Geim, Science, 324, 1530 (2009).(2) B. Anasori, M. R. Lukatskaya, and Y. Gogotsi, Nat. Rev. Mater., 2, 16098(2017).(3) V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano, and J. N. Coleman, Science, 340, 1226419 (2013).(4) C. O’Dwyer, L. Walsh, F. Gity, S. Bhattacharjee, and P. K. Hurley, Electrochem. Soc. Interface, 27, 53 (2018).(5) L. Britnell et al., Science, 340, 1311 (2013).(6) F. Xia, H. Wang, D. Xiao, M. Dubey, and A. Ramasubramaniam, Nat. Photon., 8,899 (2014).(7) E. Carroll, D. Buckley, D. Mc Nulty, and C. O’Dwyer, ECS J. Solid State Sci. Technol. 9 093015 (2020).(8) V. Sánchez, E. Benavente, V. Lavayen, C. O’Dwyer, C. M. S. Torres, G. González, and M. A. S. Ana, Appl. Surf. Sci. 252, 7941 (2006).(9) E. B. Secor, B. Y. Ahn, T. Z. Gao, J. A. Lewis, and M. C. Hersam, Adv. Mater., 27,6683 (2015).(10) D. McManus et al., Nat. Nanotechnol., 12, 343 (2017).(11) E. Carroll, D. Buckley, V. Mogili, D. McNulty, M. S. Moreno, C. Glynn, G. Collins, J. D. Holmes, K. M. Razeeb, C. O’Dwyer, Chem. Mater. 29, 7390-7400 (2017).(12) E. Carroll, D. P. Buckley, G. Collins, J. D. Holmes, K. M. Razeeb, and C. O'Dwyer, ECS Trans. 64, 1 (2015).

Controlling Nanostructure in Inkjet Printed Organic Transistors for Pressure Sensing Applications.

This work reports the development of a highly sensitive pressure detector prepared by inkjet printing of electroactive organic semiconducting materials. The pressure sensing is achieved by incorporating a quantum tunnelling composite material composed of graphite nanoparticles in a rubber matrix into the multilayer nanostructure of a printed organic thin film transistor. This printed device was able to convert shock wave inputs rapidly and reproducibly into an inherently amplified electronic output signal. Variation of the organic ink material, solvents, and printing speeds were shown to modulate the multilayer nanostructure of the organic semiconducting and dielectric layers, enabling tuneable optimisation of the transistor response. The optimised printed device exhibits rapid switching from a non-conductive to a conductive state upon application of low pressures whilst operating at very low source-drain voltages (0–5 V), a feature that is often required in applications sensitive to stray electromagnetic signals but is not provided by conventional inorganic transistors and switches. The printed sensor also operates without the need for any gate voltage bias, further reducing the electronics required for operation. The printable low-voltage sensing and signalling system offers a route to simple low-cost assemblies for secure detection of stimuli in highly energetic systems including combustible or chemically sensitive materials.

Investigation on evaluating the printable height and dimensional stability of food extrusion-based 3D printed foods

3D food printing is an emerging technology with the potential to change people's eating habits. Rheological properties of food inks are critical to their printable behavior in extrusion-based 3D printing, and there is a strong correlation between Low-field nuclear magnetic resonance (LF-NMR) parameters and rheological properties. This study aimed to investigate the relationship between the printability of food inks and materials' properties in terms of rheological properties, mechanical strength, and water mobility, and to quantify the shape stability and self-supporting behavior of 3D printed structures. Results indicated that the zero shear viscosity and Young's modulus of food inks were linearly related to the 3D printable height of samples within a certain range, and storage modulus (G′) was linearly correlated to the shape stability of printed samples. This study would provide some universal applicable information on the relationship between 3D printable height, shape stability, and food ink's material properties. • Factors affecting the 3D printable height and dimensional stability were studied. • Effect of shear viscosity and Young's modulus on 3D printable height was studied. • Relationship between storage modulus and dimensional stability was established. • A model to predict 3D printable height and dimensional stability was established.

Recent Advancement of Emerging Nano Copper-Based Printable Flexible Hybrid Electronics.

Printed copper materials have been attracting significant attention prominently due to their electric, mechanical, and thermal properties. The emerging copper-based flexible electronics and energy-critical applications rely on the control of electric conductivity, current-carrying capacity, and reliability of copper nanostructures and their printable ink materials. In this review, we describe the growth of copper nanostructures as the building blocks for printable ink materials on which a variety of conductive features can be additively manufactured to achieve high electric conductivity and stability. Accordingly, the copper-based flexible hybrid electronics and energy-critical devices printed by different printing techniques are reviewed for emerging applications.

Aerosol Jet Direct Writing Polymer-Thick-Film Resistors for Printed Electronics

To improve performance and reduce size of printed-circuit board (PCB) in electronics industry, embedding discrete components within a board substrate has been an effective approach by reducing solder joints and their associated impedance mismatching, inductive reactance, etc. With its unique capabilities for non-contact precision material deposition, the Aerosol Jet® direct-write technology has been enabling additive manufacturing of fine-feature electronics conformally onto flexible substrates of complicated shapes. The CAD/CAM controlled relative motions between substrate and print head allows convenient adjustment of the pattern and pile height of deposited material at a given ink volumetric deposition rate. To date in the printed electronics industry, additively printing embedded polymer-thick-film (PTF) resistors has mostly been done with screen printing using carbon-based paste inks. Here we demonstrate results of Aerosol Jet® printed PTF resistors of resistance values ranging from ~50 W to > 1 kW, adjustable (among several variable parameters) by the number of stacked layers (or print passes with each pass depositing a fixed amount of ink) between contact pads of around 1 mm apart with footprint line typically < 0.3 mm. In principle, any ink material that can be atomized into fine droplets of 1 to 5 microns can be printed with the Aerosol Jet® system. However, the print quality such as line edge cleanliness can significantly influenced by ink rheology which involves solvent volatility, solids loading, and so on. Our atomizable carbon ink was made by simply diluting a screen printing paste with a compatible solvent of reasonable volatility, which can be cured at temperatures below 200 oC. We show that Aerosol Jet® printed overlapping lines can be stacked to large pile height (to reduce the resistance value) without significant increase of line width, which enables fabricating embedded resistors with adjustable resistance values in a limited footprint space.

Direct Ink Writing of Materials for Electronics-Related Applications: A Mini Review

Recently, the fabrication of electronics-related components via direct ink writing (DIW) has attracted much attention. Compared to the conventionally fabricated electronic components, DIW-printed ones have more complicated structures, higher accuracy, improved efficiency, and even enhanced performances that arise from well-designed architectures. The DIW technology allows directly print materials on a variety of flat substrates, even a conformal one, well suiting them to applications such as wearable devices and on-chip integrations. Here, recent developments in DIW printing of emerging components for electronics-related applications are briefly reviewed, including electrodes, electronic circuits, and functional components. The printing techniques, processes, ink materials, advantages, and properties of DIW-printed architectures are discussed. Finally, the challenges and outlooks on the manufacture of 3D structured electronic devices by DIW are outlined, pointing out future designs and developments of DIW technology for electronics-related applications. The combination of DIW and electronic devices will help to improve the quality of human life and promote the development of science and society.

A carbon ink for use in thin, conductive, non peelable, amphiphilic, antioxidant, and large-area current collector coating with enhanced lithium ion battery performance

We reported that a stable carbon ink composed of conductive carbon materials (graphene and super P), binder (sodium carboxymethyl cellulose (CMC)), interface active agent (sodium dodecyl sulfate (SDS)), and metal coupling agent ((3-aminopropyl)triethoxysilane (APTES)) for using in coating conducting layer on cathode/anode current collector for LIBs. Graphene materials are obtained using a low-cost graphite material (KS 6) and processing it via a wet ball-milling to exfoliate single layers into the ink. The ink can be coated on the LIB current collector in a large area by a doctor blade to form a carbon layer of about 1 μm without overflow. Carbon-coated current collectors have amphiphilic properties, not peel off under extreme physical and chemical conditions, and resist oxidation under high temperature (200 °C) processing conditions. In addition, carbon-coated current collector are superior to the batteries using bare metal foil a current collectors in the LIB performance of graphite half-cell, graphite full-cell, LiFePO4 half-cell, and silicon-carbon full-cell. These results show that the carbon-coated metal foil can reduce the interface resistance with the active material and improves the adhesion of the active materials to the current collector, avoiding peeling off during charge/discharge process, thereby improving of LIBs performance. The developed method can produce high-quality, low-cost carbon material inks on a large scale through a simple and inexpensive process, and coat them evenly and finely on current collectors, making it possible to achieve efficient industrial and commercial perspectives for next-generation LIB-based current collectors.

Direct Ink Writing of Moldable Electrochemical Energy Storage Devices: Ongoing Progress, Challenges, and Prospects

Among the advanced additive manufacturing technologies, direct ink writing (DIW) technology is extensively utilized to fabricate various energy storage devices (i.e., batteries, supercapacitors [SCs], and solar cells) due to its excellent process flexibility, excellent geometric controllability, as well as relative low‐cost and efficient processes. DIW offers a convenient way to build 3D structures for energy storage devices and provide higher power density and energy density in comparison with traditional casting techniques. Herein, the recent advances in DIW for emerging energy storage devices, including SCs, lithium‐ion batteries, lithium–sulfur batteries, rechargeable lithium metal batteries, and solid‐state batteries, are emphasized and discussed. The significant achievements made developing printed energy storage devices, such as printing ink materials, designing the printing process, and the great progress in terms of the corresponding electrochemical performances, are also highlighted. Finally, the major challenges and potential research possibilities in 3D printing energy storage device are proposed. It can be expected that, as 3D printing technology develops, batteries and SCs with durable lifespans, favorable safety, as well as high energy density and power density will eventually be utilized in many fields.

3D printed gellan gum/graphene oxide scaffold for tumor therapy and bone reconstruction

Compared with traditional tissue engineering scaffold processing methods, 3D printing technology has obvious advantages in achieving high structural complexity, flexibility and specific patient needs. Printing ink materials with both high printability and biocompatibility remains a major challenge. Herein, a hydrogel bio-ink with excellent thixotropy and recovery properties was prepared by combining gellan gum (GG) and graphene oxide (GO) for extrusion 3D printing. The GG/GO scaffold constructed by 3D printing has a regular and connected porous structure, which maintains high fidelity with the model. Cell proliferation and attachment in the printed 3D curcumin-loaded scaffold revealed that the bifunctional GG/GO/Cur scaffold could inhibit human osteosarcoma cell line (MG-63) growth significantly and induce tumor cell death effectively in vitro. Simultaneously, the scaffold could support the attachment and proliferation of mouse osteoblast cell (MC3T3). Therefore, the functional GG/GO/Cur scaffold is expected to be used to repair the bone defects induced by surgery and kill the possibly residual tumor cells at the same time to achieve the purpose of tumor therapy and bone reconstruction.

Thickness/morphology of functional material patterned by topographical discontinuous dewetting

AbstractTopographical discontinuous dewetting (TDD) patterning is a nascent 2D printing technique explored for high‐throughput nanoscale patterning of functional material inks. However, variables affecting the z thickness and morphology of the deposited functional materials inside the patterned microchannels remain unexplored. We developed a theoretical model that can determine the thickness of the deposited functional material layers using the TDD patterning technique. We then confirmed the model with experimental data by depositing colloidal dispersions into microchannels using TDD patterning to systematically study the effects of different processing variables. The contribution of evaporation‐driven flow to the deposited layer thickness was significant, with the relationship of thickness to inking speed different to that previously determined for thin film blade coating of colloidal dispersions in the evaporative regime. Additionally, a viscosity dampening effect was observed, unique to TDD of microchannels, which slowed the evaporation‐driven flow due to local viscosity increase in the microchannels. Channel dimensions and ink dispersion concentration affected thickness as hypothesized. Internal flows in the microchannels normal to the sidewalls and perpendicular to the microchannel length (“coffee ring” effect capillary flow/Marangoni flow) were found to contribute significantly to the final morphology/thickness of the deposited layers for the systems/dispersions experimentally measured.

New “all-in-one” silicone pastes for additive manufacturing of elastomer parts

A new type of silicone ink materials for additive manufacturing is described. We call them “all-in-one” pastes since they contain all necessary components for efficient and practical printing, including filler(s), crosslinking systems, and necessary or desired additives. The pastes can be easily tuned for the most appropriate rheology for selected printing operation, have long shelf life stabilities for practical manipulation and storage, and enable quick and complete crosslinking by hydrosilylation at room temperature in air to facilitate permanent fixing of shapes of printed objects.

Установление давности изготовления документов: теория и практика использования в судопроизводстве

The determination of the timeframe in which a document was created is applied to verify the authenticity of documents in the investigation of fraud committed by using forged documents. It is known that the document aging process affects the substrate characteristics, the study of which requires physical and chemical research of document details. This article discusses the techniques employed to examine inks, pen pastes, gel, stamp ink and other materials that created the document. Knowledge of methods for determining the age of documents will help investigators, judges and lawyers better select experts and specialists, conduct interrogations, and evaluate their conclusions.

4D Printed Cardiac Construct with Aligned Myofibers and Adjustable Curvature for Myocardial Regeneration.

As an innovative additive manufacturing process, 4D printing can be utilized to generate predesigned, self-assembly structures which can actuate time-dependent, and dynamic shape-changes. Compared to other manufacturing techniques used for tissue engineering purposes, 4D printing has the advantage of being able to fabricate reprogrammable dynamic tissue constructs that can promote uniform cellular growth and distribution. For this study, a digital light processing (DLP)-based printing technique was developed to fabricate 4D near-infrared (NIR) light-sensitive cardiac constructs with highly aligned microstructure and adjustable curvature. As the curvature of the heart is varied across its surface, the 4D cardiac constructs can change their shape on-demand to mimic and recreate the curved topology of myocardial tissue for seamless integration. To mimic the aligned structure of the human myocardium and to achieve the 4D shape change, a NIR light-sensitive 4D ink material, consisting of a shape memory polymer and graphene, was created to fabricate microgroove arrays with different widths. The results of our study illustrate that our innovative NIR-responsive 4D constructs exhibit the capacity to actuate a dynamic and remotely controllable spatiotemporal transformation. Furthermore, the optimal microgroove width was discovered via culturing human induced pluripotent stem cell-derived cardiomyocytes and mesenchymal stem cells onto the constructs' surface and analyzing both their cellular morphology and alignment. The cell proliferation profiles and differentiation of tricultured human-induced pluripotent stem cell-derived cardiomyocytes, mesenchymal stem cells, and endothelial cells, on the printed constructs, were also studied using a Cell Counting Kit-8 and immunostaining. Our results demonstrate a uniform distribution of aligned cells and excellent myocardial maturation on our 4D curved cardiac constructs. This study not only provides an efficient method for manufacturing curved tissue architectures with uniform cell distributions, but also extends the potential applications of 4D printing for tissue regeneration.

Application of inkjet printing in the large area display of organic light-emitting diode

<p indent=0mm>As the interaction media between human beings and electronic devices, display technology has become more and more important in our daily life with the development of modern information technology such as big data technology and artificial intelligence, which also brings the huge demands on the market of large area display. Active organic light-emitting diode (OLED) is one of the most competitive candidates for the next-generation display, fulfilling the demand of vivid color, wide view angle, flexible stretchability and high contrast. Thus, OLED devices have already been widely applied in small-size displays such as smart watches, smart phones, tablet computers and automobile monitor and so on. However, currently most commercialized OLED devices are still fabricated by high-cost methods, greatly hindering their application in large area display. For example, in the commercial large area display, only white OLED technology has been practically employed regardless of its high fabrication cost which is the reason of its less sharing market occupancy. White OLED technique faces some difficulties that can hardly be solved perfectly for adopting thermal deposition process, such as poor utilization of organic materials, expensive deposition facilities and low product yields, etc. The technique of QD-OLED is another alternative method for large area display, which is the upcoming scheme Samsung promotes firmly, but it has been repeatedly delayed in the mass production because there are still some unconquered barriers in materials and manufacturing processes. According to the announcement of Samsung display company, in the next half year of 2021, the commodity of QD-OLED will be appeared finally, but it could not be sold in large quantities, which will be with high price exceeding expectation of consumer. Therefore, including TV, phone and monitor, the retail price of OLED products is much higher than that of liquid crystal display (LCD) all the time, impeding the commercial application of large area OLED. With the advantages of effective material utilization, low cost and convenient fabrication of large area panel, inkjet printing is relatively suitable for the manufacture of large area OLED display, which is the crucial developing technique to the display companies and researching institutes. Except the immaturity of industrial inkjet machine and process, the efficiency and stability of OLED based on inkjet printing can’t satisfy the requirements of commercialized application. Consequently, it is significant that OLED based on inkjet printing with high efficiency and long lifetime is realized and marketed by improving ink materials, devices and processes to achieve low price and outstanding performance. In this paper, starting with descripting the current status of large area OLED display, we briefly introduce the recent progresses of inkjet printing OLED and relevant materials and devices, as well as their applications in large area display. Finally, we present our ideas about the future developing direction of new display of OLED based on inkjet printing technology.

3D bioprinting of graphene oxide-incorporated cell-laden bone mimicking scaffolds for promoting scaffold fidelity, osteogenic differentiation and mineralization

Bioprinting is a promising technique for facilitating the fabrication of engineered bone tissues for patient-specific defect repair and for developing in vitro tissue/organ models for ex vivo tests. However, polymer-based ink materials often result in insufficient mechanical strength, low scaffold fidelity and loss of osteogenesis induction because of the intrinsic swelling/shrinking and bioinert properties of most polymeric hydrogels. Here, we developed a human mesenchymal stem cells (hMSCs)-laden graphene oxide (GO)/alginate/gelatin composite bioink to form 3D bone-mimicking scaffolds using a 3D bioprinting technique. Our results showed that the GO composite bioinks (0.5GO, 1GO, 2GO) with higher GO concentrations (0.5, 1 and 2 mg/ml) improved the bioprintability, scaffold fidelity, compressive modulus and cell viability at day 1. The higher GO concentration increased the cell body size and DNA content, but the 2GO group swelled and had the lowest compressive modulus at day 42. The 1GO group had the highest osteogenic differentiation of hMSC with the upregulation of osteogenic-related gene (ALPL, BGLAP, PHEX) expression. To mimic critical-sized calvarial bone defects in mice and prove scaffold fidelity, 3D cell-laden GO defect scaffolds with complex geometries were successfully bioprinted. 1GO maintained the best scaffold fidelity and had the highest mineral volume after culturing in the bioreactor for 42 days. In conclusion, GO composite bioinks had better bioprintability, scaffold fidelity, cell proliferation, osteogenic differentiation and ECM mineralization than the pure alginate/gelatin system. The optimal GO group was 1GO, which demonstrated the potential for 3D bioprinting of bone tissue models and tissue engineering applications.

A low-cost printed organic thermoelectric generator for low-temperature energy harvesting

Global warming and pollution resulted from the increased power demand are some of the present era challenges associated with power generation through fossil fuels. To provide a solution, renewable energy systems are gaining much interest to capture energy through different energy harvesting devices. Among the energy harvesting devices, the thermoelectric generators (TEGs) are the ones with the ability to directly convert thermal energy into electrical energy without any environmental effects. However, their conventional fabrication methods are costly and possess environmental effects. This research reports an organic TEG fabricated through a cost-efficient and environmentally friendly process known as the direct ink write technique. The TEGs are printed onto a glass substrate, the most common insulator used in houses, and building windows with two different lengths. The active materials used are poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) ink which is an organic semiconducting material and silver ink. The maximum power outputs of 5.17 ± 0.5 nW and 4.08 ± 0.5 nW are recorded for TEGs with different characteristic lengths of 30 and 40 mm at a temperature gradient of 120 °C. Furthermore, the performance of TEG is also characterized for solar thermal energy harvesting. The results obtained are reasonably linear, stable, and comparable to previously reported.