While electroporation has been widely used as a physical method for gene transfection in vitro and in vivo, its application in gene therapy of cardiovascular cells remains challenging. Due to the high concentration of ion-transport proteins in the sarcolemma, conventional electroporation of primary cardiomyocytes tends to cause ion-channel activation and abnormal ion flux, resulting in low transfection efficiency and high mortality. In this work, we report a high-throughput nano-electroporation technique based on a nanochannel array platform, which enables massively parallel delivery of genetic cargo (microRNA, plasmids) into mouse primary cardiomyocytes in a controllable, highly efficient and benign manner. A simple ‘dewetting’ approach was implemented to precisely position a large number of cells on the nano-electroporation platform. With dosage control, our device precisely titrated the level of miR-29, a potential therapeutic agent for cardiac fibrosis, and determined the minimum concentration of miR-29 causing side effects in mouse primary cardiomyocytes. Moreover, the dose-dependent effect of miR-29 on mitochondrial potential and homeostasis was monitored. Altogether, our nanochannel array platform provides efficient trapping and transfection of primary mouse cardiomyocyte, which could improve the quality control for future microRNA therapy in heart diseases.

Supercapacitors, based on fast ion transportation, are specialized to provide high power, long stability, and efficient energy storage using highly porous electrode materials. However, their low energy density excludes them from many potential applications that require both high energy density and high power density performances. Using a scalable nanoporous graphene synthesis method involving an annealing process in hydrogen, here we show supercapacitors with highly porous graphene electrodes capable of achieving not only a high power density of 41 kW kg and a Coulombic efficiency of 97.5%, but also a high energy density of 148.75 Wh kg. A high specific gravimetric and volumetric capacitance (306.03 F g and 64.27 F cm) are demonstrated. The devices can retain almost 100% capacitance after 7000 charging/discharging cycles at a current density of 8 A g. The superior performance of supercapacitors is attributed to their ideal pore size, pore uniformity, and good ion accessibility of the synthesized graphene.

Epitaxial SrRuO3 (SRO) films with BaTiO3 buffer layer are deposited on mica substrates by pulsed laser deposition. The flexible film layers are subsequently prepared by mechanical exfoliation. The impact of mechanical strain on the magnetic properties of SRO is investigated. To control the applied mechanical strain, the prepared SRO films are firmly attached onto convex molds with different radii of curvature. The magnetization measurements are performed on SRO films under different mechanical strains. It is found that the magnetic properties of SRO films, including Curie temperature, saturated magnetic moment, and coercive field, depend strongly on the mechanical strain. The saturated moment can be enhanced from 1.2 to 3.2 µB per Ru by applying a compressive mechanical strain, which is presumably attributed to a spin state transition. The magnetic anisotropy can be varied as well by exerting mechanical compressive or tensile strain. The flexible SRO films on mica substrate with highly tunable magnetic properties show a great potential for novel applications in flexible electronics.

No abstract

Vanadium dioxide (VO) is a strong-correlated metal-oxide with a sharp metal-insulator transition (MIT) for a range of applications. However, synthesizing epitaxial VO films with desired properties has been a challenge because of the difficulty in controlling the oxygen stoichiometry of VO , where x can be in the range of 1< x < 2.5 and V has multiple valence states. Herein, a unique moisture-assisted chemical solution approach has been developed to successfully manipulate the oxygen stoichiometry, to significantly broaden the growth window, and to significantly enhance the MIT performance of VO films. The obvious broadening of the growth window of stoichiometric VO thin films, from 4 to 36 °C, is ascribed to a self-adjusted process for oxygen partial pressure at different temperatures by introducing moisture. A resistance change as large as 4 orders of magnitude has been achieved in VO thin films with a sharp transition width of less than 1 °C. The much enhanced MIT properties can be attributed to the higher and more uniform oxygen stoichiometry. This technique is not only scientifically interesting but also technologically important for fabricating wafer-scaled VO films with uniform properties for practical device applications.