New experiments by researchers at The University of Manchester have placed the best limits yet on impermeability of graphene and other two-dimensional materials to gases and liquids. [37] Microfluidic paper-based analytical devices (µPADs) are a promising concept with rapid development in recent years. [36] When it comes to batteries, there are always areas for improvement: the race is on to develop batteries that are cheaper, safer, longer lasting, more energy dense, and easily recyclable. [35] Grain boundaries are one of the most prominent defects in engineering materials separating different crystallites, which determine their strength, corrosion resistance and failure. [34] Ferroelectric materials have a spontaneous dipole moment which can point up or down. [33] Researchers have successfully demonstrated that hypothetical particles that were proposed by Franz Preisach in 1935 actually exist. [32] Scientists from the Department of Energy's SLAC National Accelerator Laboratory and the Massachusetts Institute of Technology have demonstrated a surprisingly simple way of flipping a material from one state into another, and then back again, with single flashes of laser light. [31] Materials scientists at Duke University computationally predicted the electrical and optical properties of semiconductors made from extended organic molecules sandwiched by inorganic structures. [30] KU Leuven researchers from the Roeffaers Lab and the Hofkens Group have now put forward a very promising direct X-ray detector design, based on a rapidly emerging halide perovskite semiconductor, with chemical formula Cs2AgBiBr6. [29] Physicists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have proven that incoming light causes the electrons in warm perovskites to rotate, thus influencing the direction of the flow of electrical current. [28]