Graphical Abstract Highlights d Positive force frequency and post-rest potentiation are achieved in human tissues d Engineered atrial and ventricular tissues have distinct electrophysiology and drug responses d Atrio-ventricular tissues show spatially confined drug responses d Long-term electrical conditioning enables polygenic cardiac disease modeling SUMMARYTissue engineering using cardiomyocytes derived from human pluripotent stem cells holds a promise to revolutionize drug discovery, but only if limitations related to cardiac chamber specification and platform versatility can be overcome. We describe here a scalable tissue-cultivation platform that is cell source agnostic and enables drug testing under electrical pacing. The plastic platform enabled on-line noninvasive recording of passive tension, active force, contractile dynamics, and Ca 2+ transients, as well as endpoint assessments of action potentials and conduction velocity. By combining directed cell differentiation with electrical field conditioning, we engineered electrophysiologically distinct atrial and ventricular tissues with chamber-specific drug responses and gene expression. We report, for the first time, engineering of heteropolar cardiac tissues containing distinct atrial and ventricular ends, and we demonstrate their spatially confined responses to serotonin and ranolazine. Uniquely, electrical conditioning for up to 8 months enabled modeling of polygenic left ventricular hypertrophy starting from patient cells.

The volume expansion behavior of low‐density polypropylene foams in extrusion is investigated in this paper. Since escape of blowing agent from the foam would cause the foam to contract, and to have low expansion, efforts were made to prevent gas loss during foaming. The basic strategies to the promotion of a large volume expansion ratio are: to use a branched material for preventing cell coalescence; to use a long‐chain blowing agent with low diffusivity; to lower the melt temperature for decreasing gas loss during expansion; and to optimize the processing conditions in the die for avoiding too‐rapid crystallization. Use of a branched polypropylene resin was required to achieve large volume expansion because prevention of cell coalescence will retard gas loss from the extruded foam to the environment. The foam morphologies of linear and branched polypropylene materials at various processing temperatures were studied using a single‐screw tandem foam extrusion system and their volume expansion behaviors were compared. Ultra lowdensity, fine‐celled polypropylene foams with very high expansion ratio up to 90 fold were successfully produced from the branched polypropylene resins.

This article describes the fundamental foaming mechanisms that governed the volume expansion behavior of extruded polypropylene (PP) foams. A careful analysis of extended experimental results indicated that the final volume expansion ratio of the extruded PP foams blown with butane was governed by either the loss of the blowing agent or the crystallization of the polymer matrix. A charge coupling device (CCD) camera was installed at the die exit to carefully monitor the shape of the extruded PP foams. The CCD images were analyzed to illustrate both mechanisms, gas loss and crystallization, during foaming at various temperatures, and the maximum expansion ratio was achieved when the governing mechanism was changed from one to the other. In general, the gas loss mode was dominant at high temperatures and the crystallization mode was dominant at low temperatures. When the gas loss mode was dominant, the volume expansion ratio increased with decreasing temperature because of the reduced amount of gas lost. By contrast, when the crystallization mode was dominant, the expansion ratio increased with increasing temperature because of the delayed solidification of the polymer. The processing window variation with the butane concentration, the change in the temperature ranges for the two governing modes, and the sensitivity of melt temperature variations to the volume expansion ratio are discussed in detail on the basis of the obtained experimental results for both branched and linear PP materials.

In this study, linear homopolypropylene/clay (HPPC) nanocomposite foams with a high expansion ratio of about 18 and a high cell density of about 1.7 × 10 8 cells/cm 3 were produced using an extrusion foaming method with CO 2 as the physical blowing agent. The result was much better than pure HPP foams with expansion ratios of 1.7-2.2 and cell densities of 10 3 -10 5 cells/cm 3 obtained even at the same foaming conditions. The nanoclays had a half-exfoliated structure in the HPP matrix, and their presence dramatically affected the viscoelastic properties of HPP melt and foaming behaviors. It was found that the introduction of a small amount of nanoclay significantly increased the cell morphology of HPP foams at low die temperatures, where the cell wall was very thin and cell distribution was uniform. With an increase in nanoclay content of up to 5 wt %, cell morphology was improved gradually at broader die temperatures. Based on the cell morphology results, a suitable foaming window for clay content and die temperature was established. The mechanisms behind these phenomena are discussed from the perspective of cell nucleation and coalescence. Microstructures were found in the cell walls of HPP and HPPC nanocomposite foams, and they tended to evolve with cell wall thickness, depending on the die temperatures. Scanning electron microscopy (SEM) observation of foams and solvent-etched foams revealed that the microstructures in the cell walls were formed by covering large-sized crystals and that the absence of microstructures was due to the presence of smallsized crystals in the cell walls. A distribution of crystal sizes was observed across the foamed samples, which was affected by the die temperature and the introduction of nanoclay. The possible reasons were elaborated by considerations of temperature gradient. DSC tests indicated that the foaming process induced a lowtemperature peak (T m1 ) and its heat of fusion (∆H m1 ) tended to evolve with the die temperature and the introduction of nanoclay.

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(2016). Novel pliable electrodes for flexible electrochemical energy storage devices: recent progress and challenges. Advanced Energy Materials, 6(17). which has been published in final form at 10.1002/aenm.201600490 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. How to cite TSpace itemsAlways cite the published version, so the author(s) will receive recognition through services that track citation counts, e.g. Scopus. If you need to cite the page number of the author manuscript from TSpace because you cannot access the published version, then cite the TSpace version in addition to the published version using the permanent URI (handle) found on the record page.

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In this study, the effects of nanoclay on the mechanical properties of poly(methylmethacrylate) (PMMA)/clay nanocomposite foams are investigated. Intercalated PMMA/clay nanocomposites have been prepared through a solvent co-precipitation method. PMMA/clay nanocomposites with only 0.5 wt% of well-dispersed montmorillonite nanoclay showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength, and elongation at break. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. Microcellular foams have been processed with PMMA/clay nanocomposite material using a subcritical gas foaming method. When a short foaming time is used, the increased amount of nanoclay induced a greater amount of heterogeneous nucleation during the foaming process and therefore decreased the density of the foam. In contrast, when a longer foaming time is used, foam density increased with a larger nanoclay load due to the higher diffusivity coefficient of CO2 blowing agent. Nanoclay, as a nucleation agent and reinforcement filler, changed the foaming behavior and mechanical properties of the PMMA microcellular foams. The microcellular foams made of PMMA/clay nanocomposite with 0.5 wt% exhibited an optimized mechanical response under tensile experiments. It is observed that the mechanical properties of nanocomposite foams are greatly related to the mechanical properties of unfoamed material and foam density. The nanoclay dispersion quality is a very important factor for the mechanical properties of both foamed and unfoamed polymer/clay nanocomposites.