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An ultra-thin, stretchable, and transparent hydrogenbonded poly(ethylene oxide) and poly(acrylic acid) ([PEO/PAA] n ) bilayer (BL) positive triboelectric film was developed using a low-cost and eco-friendly layer-by-layer method. [PEO/PAA] n films exhibited remarkable output performance, enabling designability, foldability, and sustainability for versatile application of triboelectric nanogenerators (TENGs). The dependence of TENG behaviors on thickness was investigated by varying the number of BLs in [PEO/PAA] n films. It was demonstrated that a 1.6-μm-thick [PEO/PAA] 20 TENG resulted in an optimal electrical output performance of 303 V and 36.1 mA m −2 , owing to a higher affinity for electron donation and the lowest work function. A free-standing (FS) skin-like [PEO/PAA] 100 TENG was designed for shape-adaptive kirigami-type nanogenerators, exhibiting ∼100% ultrahigh transparency, ∼900% super-stretchability, and extraordinary foldability to 1/32 its original size. Thus, FS-TENG could be attached to the skin, a wall, or the insole of a shoe, showing an output of 321, 501, and 319 V, respectively, enough to simultaneously turn on 39 green LEDs by manually tapping or running.

Serious climate changes and energy-related environmental problems are currently critical issues in the world. In order to reduce carbon emissions and save our environment, renewable energy harvesting technologies will serve as a key solution in the near future. Among them, triboelectric nanogenerators (TENGs), which is one of the most promising mechanical energy harvesters by means of contact electrification phenomenon, are explosively developing due to abundant wasting mechanical energy sources and a number of superior advantages in a wide availability and selection of materials, relatively simple device configurations, and low-cost processing. Significant experimental and theoretical efforts have been achieved toward understanding fundamental behaviors and a wide range of demonstrations since its report in 2012. As a result, considerable technological advancement has been exhibited and it advances the timeline of achievement in the proposed roadmap. Now, the technology has reached the stage of prototype development with verification of performance beyond the lab scale environment toward its commercialization. In this review, distinguished authors in the world worked together to summarize the state of the art in theory, materials, devices, systems, circuits, and applications in TENG fields. The great research achievements of researchers in this field around the world over the past decade are expected to play a major role in coming to fruition of unexpectedly accelerated technological advances over the next decade.

Because of self-renewal, strong proliferation in vitro, abundant sources for isolation, and a high differentiation capacity, mesenchymal stem cells are suggested to be potentially therapeutic for liver fibrosis/cirrhosis. In this study, we evaluated the treatment effects of mouse bone marrow-derived mesenchymal stem cells (BM-MSCs) on mouse liver cirrhosis induced by carbon tetrachloride. Portal and tail vein transplantations were examined to evaluate the effects of different injection routes on the liver cirrhosis model at 21 days after transplantation. BM-MSCs transplantation reduced aspartate aminotransferase/alanine aminotransferase levels at 21 days after injection. Furthermore, BM-MSCs induced positive changes in serum bilirubin and albumin and downregulated expression of integrins (600- to 7000-fold), transforming growth factor, and procollagen-α1 compared with the control group. Interestingly, both injection routes ameliorated inflammation and liver cirrhosis scores. All mice in treatment groups had reduced inflammation scores and no cirrhosis. In conclusion, transplantation of BM-MSCs via tail or portal veins ameliorates liver cirrhosis in mice. Notably, there were no differences in treatment effects between tail and portal vein administrations. In consideration of safety, we suggest transfusion of bone marrow-derived mesenchymal stem cells via a peripheral vein as a potential method for liver fibrosis treatment.