In this research, a 3D printing technique was employed for processing biobased composites of polyacrylated epoxidized soybean oil (AESO) with modified ethyl cellulose macromonomer (ECM). In this 3D printing process, objects are built in a layer-by-layer fashion by depositing formulated liquid solutions on a platform and rapidly transformed into a solid film cured by UV light. The sustainable materials consisting of ECM and AESO biopolymer were examined for their physical and thermal properties. Samples with different ECM and AESO weight ratios were prepared. Tensile test results showed the ECM-AESO composites had higher strength and stiffness than AESO alone. Their tensile strengths with ECM weight contents from 30 wt.% to 5 wt.% are between 11.5 MPa and 5.9 MPa and Young's moduli are between 167 MPa and 56 MPa, compared to AESO polymer itself with 4.3 MPa and 27.4 MPa, respectively. Further, the glass transition temperatures of all ECM-AESO composites were increased from 57.4 to 82.2 degrees C, compared to AESO polymer itself with 47.1 degrees C. Thermal properties of the ECM-AESO composites are stable up to 325 degrees C. These materials may be of great environmental interest because these composites consist of high amounts of agricultural resources.

We report living electrode materials from green algae “Chlorella vulgaris” embedded within alginate hydrogel and cross-linked at different calcium chloride concentrations.

Bioprinters are being extensively used for different applications in life sciences and medicine in general and more specifically in regenerative medicine, tissue, and organ fabrication. The technology has matured from its purely academic origin owing to the involvement of materials science, engineering, biology, and physics, as well as commercial entities. Nevertheless, despite the progress in the science and the understanding of the mechanisms underlying the various bioprinting technologies, further efforts are needed to develop more quantitative strategies. In particular, predictive modeling is necessary to optimize the printing parameters and thus enhance the quality of the final products. Here, we review the physics that underpins the most commonly employed approaches, such as extrusion, laser-based, and inkjet bioprinting. We provide an overview of the relevant parameters, their inter-relationships, and the equations that govern the various printing processes and thus allow for their optimization. We present our perspective on the field and views on future strategies for its further advancement. Our intention with this review is to provide the practitioners of bioprinting with additional tools to enhance the quantitative aspects of their work and move the technology beyond its early, mostly trial and error character.

The most developed route to inkjet printed metal conductors employs nanoparticle silver inks. There are significant problems in formulating stable, concentrated silver inks and the cost of producing the nanoparticles is high. An alternative is to print two solutions simultaneously, for instance solutions of a metal salt and a reducing agent. The metal then forms on the substrate. While there are unsolved problems in turning this into a practical technology, there are many choices of solutions, substrates and conditions that are unexplored. It does have the advantage over the nanoparticle approach of relaxing many of the constraints coming from needing an ink that both has good fluid properties and forms good conducting films. These issues relating to reactive inkjet printing of metals and recent studies are reviewed.

We fabricated electrically conductive textiles via vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) layers on cotton, cotton/poly(ethylene terephthalate) (PET), cotton/Lycra, and PET fabrics. We then measured the electrical resistivity values of such PEDOT-coated textiles and analyzed the effect of water treatment on the electrical resistivity. Additionally, we tested the change in the electrical resistance of the conductive textiles under cyclic stretching and relaxation. Last, we characterized the uniformity and morphology of the conductive layer formed on the fabrics using scanning electron microscopy and electron-dispersive X-ray spectroscopy.

Chlorella is a green, photosynthetic single-celled genus of algae. It can be 3D printed as a suspension in sodium alginate and gelled with calcium solutions. We have made “log pile” structures with channels between the gel lines to allow easy transport of nutrients and products. Under white light and immersed in solutions of bicarbonate and phosphate and urea “plant food” the algae multiply with the gel and produce oxygen at a rate comparable to that reported for suspensions of Chlorella. The system is stable for one or two weeks at least. In principle this can be extended to other plant tissues but there are concerns relating to bacterial and fungal infection and toxicity of the gel components. In addition a tougher gel is needed if this was to be converted to a practical bioreactor system.

Electroluminescence offers a versatile and simple route to printed light sources. A layer of poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) was inkjet printed onto polyethylene terephthalate (PET) mesh fabrics. The conductivity–transparency relationship is determined for textile-based conductors with different thicknesses of the printed PEDOT:PSS film. Alternating current powder electroluminescent devices were made by extrusion printing a layer of phosphor onto aluminum foil and then covering this with a fabric electrode. These devices are compared with indium tin oxide (ITO) glass electrodes on a similar device. Textiles coated with conducting polymers are a potential alternative to coated polymer films for flexible, transparent conductors. The strain response of these electrodes was improved by incorporating carbon nanotubes into the conductor. These bridge cracks that form on stretching.

Biomimetic materials generally refer to a material with some essential properties inspired from nature. The notion has been applied to materials, particularly with a view to producing ceramic and composite materials with improved properties. This article reviews the concept and applications of biomimesis which has now spread to include a group of loosely linked goals in new materials and processes. Synthetic approaches for inorganic particles formation are to grow them within a predefined space (micromold). Toughness of ceramic and composite materials can be improved by adding polymeric layers from very fibrous structures. The formation of synthetic polymers with a better control of the sequence of units along a chain can happen through polymerizations based on enzyme-like catalytic activity. There is a growing interest in developing synthetic materials with self-assembly capability since it is a symbol of biological systems. Processing methods of biomimetic materials are based on freeform fabrication methods which allow objects to be built as a series of layers. The applications of biomimesis in biomedical engineering include the development of biodegradable materials such as tissue-engineered implants as well as new biomedical devices combining biological structures with electronics in sensors and actuators.

Numerical models were established to correlate with the experimentally measured properties of mesh conductors previously developed through a combined process of dip coating carbon nanotubes and inkjet printing poly 3,4-ethylenedioxythiophene: poly styrene sulfonate. The electroluminescent (EL) devices assembled with such mesh conductors as front electrodes were modeled by commercially available finite element method software COMSOL Multiphysics. The modeling results are in agreement with those from the experiments and suggest that an optimized fiber arrangement is the key for further improving the performance of EL devices based on mesh conductors.

Electro-stimulated release was established using a novel, electro-conductive hydrogel system comprising Jeffamine polyetheramine and polyethylene glycol diglycidyl ether (PEGDGE) that was composited with reduced graphene oxide (rGO). The swelling response, morphology, mechanical and electrochemical properties of the composite hydrogel were investigated. Enhanced mechanical and electrical properties were observed with increased rGO content. Passive and electro-stimulated release of methyl orange (MO) from these gels was examined. A significant reduction in passive release of the dye was observed by incorporating rGO. Upon electrical stimulation, the release rate and dosage could be tuned through variation of the % w/w rGO, as well as the polarity and amplitude of the applied electric potential. A high level of control and flexibility was achieved demonstrating the applicability of this system for localised drug delivery applications.

A pH-responsive hydrogel composed of an aliphatic diamine cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) using a single, rapid polymerisation step has been used to detect glucose by entrapping glucose oxidase (GOx) within its cationic network. The swelling response of hydrogel disks on exposure to glucose were optimised through variation of factors including the cross-linking density of the network, GOx loading and the addition of catalase. Hydrogel-modified carbon cloth electrodes were also prepared and characterised using voltammetric and impedimetric techniques. Non-faradaic electrochemical impedance spectroscopy (EIS) and gravimetry were both employed to track the swelling response of the gels quantitatively. The clear potential of utilising impedance to transduce hydrogel swelling was demonstrated where a linear decrease in gel resistance (Rgel) corresponding to the swelling response was observed in the range 1 to 100 μM. A dramatic increase in the limit of detection of six orders of magnitude over the gravimetric measurement was achieved (from 0.33 mM to 0.08 μM). This increased sensitivity, coupled with the textile-based electrode substrate approach opens the potential applicability of this system for monitoring glucose concentration via the skin by sweat or interstitial fluid (ISF).

An experimental investigation on the effects of in vitro hydrolytic and enzymatic degradation on mechanical properties of polyglactin 910 monofilament sutures was performed by conducting nanoindentation studies using an atomic force microscope (AFM). For hydrolytic degradation, the sutures were incubated in phosphate buffered saline (PBS) solution at three different pH conditions, 5, 7.4, and 10. For enzymatic degradation, esterase was employed at pH condition of 7.4. The property of the sutures changed with time at different conditions were investigated by nanoindentation, tensile test experiments, image analysis using both of scanning electron microscopy (SEM) and AFM, and also Fourier transform infrared spectroscopy (FTIR). The effects of degradation on gradation of Young's modulus values across the cross section of the sutures were studied by doing progressive nanoindentation from center to surface. FTIR studies revealed the formation of new hydroxyl bonds due to both hydrolytic and enzymatic degradations. Nanoindentation results indicated that the degradation does not cause a gradient of Young's modulus of the polyglactin 910 monofilament sutures across the cross section from center to surface at different degradation times for both hydrolytic and enzymatic degradations. However, in general, the Young's modulus of all samples was decreased over 4 weeks of degradation. The microscopic evaluation of the samples also showed both qualitative changes in surface morphology and quantitative changes in surface roughness on the surface of degraded sutures. This study provided a deep understanding of the polyglactin sutures subjected to in vitro hydrolytic and enzymatic degradation, and also opened a new avenue to study the biomaterials at nano-scale.

Three-dimensional (3D) patterning and engineering of biomaterials and biointerfaces have helped bioengineers harness the full potential of cell immobilization for different biomedical applications. However, the bioengineering of an efficient cell immobilized tool, having application in cell biology and tissue engineering, often comes into realization only when a cell friendly immobilization technique is combined with a compatible 3D patterning scheme. We have previously demonstrated the successful blue light induced photopolymerization of poly (ethyleneglycol) diacrylate (PEGDA) based hydrogels for the entrapment of Saccharomyces cerevisiae and NIH 3T3 fibroblast cells. In the present work we have modified rheology of the prepolymer solution by mixing fumed silica nanofiller in different concentrations. Here we demonstrate the rapid prototyping of cell immobilized nanocomposite hydrogels, where S. cerevisiae loaded nanofilled prepolymer solution was directly written in layer-by-layer fashion using solid free form fabrication also known as rapid prototyping technique and was cross-linked into 3D cell loaded construct via blue light induced polymerization. The swelling trend was found to be a function of silica nanofiller concentration and transitioned from decreasing to increasing type at 10% w/v nanofiller concentration. Dynamic swelling profile predicted that the swelling agent transported with in the gels via super case II type transport mechanism irrespective of the crosslink density. In contrast, the mode of transportation of the loaded solute was found to be fickian and nonfickian type respectively for loosely and tightly crosslinked gels. Spatial heterogeneity in the crosslinked network was resulted upon blue light curing, subsequently the 3D growth of the immobilized cells was observed to be a function of crosslink density. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3237–3249, 2015.

The mechanical characteristics of ionic-covalent entanglement hydrogels consisting of combinations of the biopolymers gellan gum and kappa-carrageenan, and the synthetic polymers polyacrylamide and an epoxy amine were investigated. Compression testing showed that these gels exhibited “double network” behavior, i.e. strong tough gels.

Ultraviolet radiation can cause significant degradation of skin, pharmaceuticals, and other materials. Previous work has shown that encapsulation of ultraviolet sensitive molecules or proximity to protective molecules can provide protection from photo-oxidation. This study explores the protective capacity of uniform polymeric particles containing both ultraviolet sensitive materials (beta-carotene) and ultraviolet protective materials (ultraviolet absorbers oxybenzone, avobenzone, and octyl-4-methoxycinnamate and the antioxidant vitamin E). Oxybenzone and avobenzone provided the most protection when used singly and provided the best protection overall when paired with vitamin E, preserving over 80% of the beta-carotene after 60 min of exposure. Ultraviolet absorber combinations did not show a synergistic effect due to photosensitization. (C) 2013 Elsevier Ltd. All rights reserved.

Recently there has been growing interest in developing smart photovoltaic fabric devices. These devices could be used as a sustainable and ubiquitous power source for wearable and other electronic devices. Three woven photovoltaic fabric structures were constructed with fiber-shaped organic photovoltaic wire from Konarka Technologies, Inc. (Lowell, MA, USA). The organic photovoltaic wire is a flexible, lightweight and wire shaped organic photovoltaic fiber based on bulk hetero-junction nanocomposites.The power conversion characteristics of photovoltaic fabrics developed were thoroughly investigated. It was found that the power conversion efficiency of the photovoltaic fabric depends on the incident light quality; fabric cover factor, swatch size, and fabric weave structure. This study also includes photovoltaic fabric model for understanding the effects of different fabric geometry on power conversion efficiency of photovoltaic fabrics. The model predicts the performance of the photovoltaic fabrics with different shape, size and structures, and it provides design criteria for more efficient photovoltaic fabric device.

A ‘one pot’ preparation of interpenetrating polymer network hydrogels with double network characteristics is presented. A small addition of biopolymer dramatically increases the stiffness and strength of the epoxy-amine gels without affecting the large strain at failure value.

An obvious parallel of structure and function exists between a rhinoceros and a tank, and between a beetle shell and the skin of an aircraft. We can also draw comparisons at the microstructural level between these biological and synthetic materials. Significant differences also exist, however, and the rigid biological materials such as bone and shell have much to teach us. In particular, they are distinctly composite structures. Although they bear loads in much the same way as synthetic composites or ceramics, they have far more complex architectures.The goal in considering the group of mineralized biological materials as described, for example, in the article by Fink et al. in this issue, and in devising modifications of them, which is the focus of this article and of Mann's, is to learn to devise arrangements of synthetic materials that work more efficiently than the homogeneous substances of simple composites that we use now. In addition to designing better microstructural arrangements we may also learn, again by analogy to the biological materials, how best to process these structures and how to recycle them after use.Biological structural materials are optimized for their high strength- or stiffness-to-weight ratio. Achieving this in synthetic materials for nonbiological application, for example in cars and airplanes, would be of obvious value. Our own interest here has focused on cuticle and bone as models for our synthetic work. Another property of biomineralized materials, for example biological ceramics, is their increased toughness. In this case we will discuss tooth enamel mimicking.

beta-Carotene was used as a probe to investigate the protection offered by 2-ethylhexyl 4-methoxycinnamate, a photostabilizer, upon ultraviolet-A photodegradation. beta-Carotene and 2-ethylhexyl 4-methoxycinnamate were arranged in two distinct macroscopic configurations (core/shell and homogenous) in solution with tandem and single cuvettes. 2-Ethylhexyl 4-methoxycinnamate was also combined with poly(methyl methacrylate) in solution to investigate the protective synergy between the photostabilizer and the polymer matrix. The choice of configuration played a more dominant role than the concentration of 2-ethylhexyl 4-methoxycinnamate in the degradation of beta-carotene. with beta-carotene remaining more stable in the homogeneous configuration. Changing configurations yielded different proximities of 2-ethylhexyl 4-methoxycinnamate to beta-carotene; closing the proximity increased the potential close interactions (<1 nm) where transfer of excited state energy from beta-carotene to 2-ethylhexyl 4-methoxycinnamate could occur resulting in increased photostability. The addition of poly( methyl methacrylate) had a negligible impact on the decay of beta-carotene in both configurations. (C) 2011 Elsevier Ltd. All rights reserved.