Selective ion transport through three-dimensionally interconnected nanopores of quaternized block copolymer membranes for energy harvesting application.

A concentration gradient in an aqueous solution is a promising source of energy that can be converted into electrical energy by an ion-exchange polymer membrane. In concentration-gradient energy harvesters, ion transport through nanoporous channels is an emerging approach to enhance the energy conversion efficiency. Since massive but selective ion transport could be realized through nanochannels, the theoretical calculations predicted that nanoporous membranes can extract significantly larger energy than the conventional non-structured membranes. In this regard, scientists in the field have attempted to produce nanoporous membranes on a macroscopic scale based on 1D, 2D, and 3D materials. However, the fabrication of nanoporous membranes is often accompanied by technical difficulties, which entails high production cost, low throughput, and poor scalability. In this study, we took advantage of the self-segregating properties of block copolymers (BCPs) to address these issues. In particular, the non-solvent-induced phase separation method has been utilized to produce three-dimensionally interconnected nanopores within BCP membranes. In addition, the neutral BCP nanopores' surface was modified with positive charges to allow selective diffusion of anions in concentration-gradient cells. By mounting the porous BCP membranes between two aqueous solutions with different concentrations, we studied the BCP-membrane-mediated energy-harvesting performance.

Dielectric control of porous polydimethylsiloxane elastomers with Au nanoparticles for enhancing the output performance of triboelectric nanogenerators.

Taking advantage of the triboelectrification effect and electrostatic induction, triboelectric nanogenerators (TENGs) provide a simple and efficient path to convert environmental mechanical energy into electric energy. Since the generation of surface charges and their density on triboelectric materials are the key factors in determining TENG performance, many efforts have been undertaken to engineer the structures and chemistry of triboelectric materials. Among others, dielectric control of triboelectric materials is an emerging approach because the dielectric constant is intimately correlated with the capacitance of materials. In this regard, we prepared porous polydimethylsiloxane (PDMS) composites decorated with Au nanoparticles (NPs), which was designed to engineer the compressibility and dielectric constant of PDMS elastomer. To this end, a polydopamine layer was synthesized on the PDMS surface to facilitate the homogeneous deposition of Au NPs. Unlike untreated PDMS sponges, Au NPs were efficiently coated onto polydopamine-treated PDMS sponges to increase the dielectric constant. When the resulting porous NP-PDMS composites were assembled into TENG devices, the electrical output of the TENGs initially improved but decreased with the amount of Au NPs. This trade-off relationship has been discussed in terms of charge generation on the air surface and pores of NP-PDMS composites based on a recent experimental model.

RETRACTED: Evidence of a pluripotent human embryonic stem cell line derived from a cloned blastocyst.

Somatic cell nuclear transfer (SCNT) technology has recently been used to generate animals with a common genetic composition. In this study, we report the derivation of a pluripotent embryonic stem (ES) cell line (SCNT-hES-1) from a cloned human blastocyst. The SCNT-hES-1 cells displayed typical ES cell morphology and cell surface markers and were capable of differentiating into embryoid bodies in vitro and of forming teratomas in vivo containing cell derivatives from all three embryonic germ layers in severe combined immunodeficient mice. After continuous proliferation for more than 70 passages, SCNT-hES-1 cells maintained normal karyotypes and were genetically identical to the somatic nuclear donor cells. Although we cannot completely exclude the possibility that the cells had a parthenogenetic origin, imprinting analyses support a SCNT origin of the derived human ES cells.