Electrospun core-shell microfiber separator with thermal-triggered flame-retardant properties for lithium-ion batteries

or the past 50 years, semiconductor physics has played a vital role in almost every aspect of modern technology. Advances in this field have let scientists tailor the conducting properties of certain materials and initiate the transistor revolution in electronics. New research suggests that we might now be able to tailor the properties of light. The key in achieving this goal lies in the use of a new class of materials called photonic crystals, 1 whose underlying concept stems from Eli Yablonovitch's 2 and Sajeev John's pioneering work. 3 The basic idea is to design materials that can affect photon properties in much the same way that ordinary semiconductor crystals affect electron properties. You achieve this control by constructing a crystal consisting of a periodic array of macroscopic uniform dielectric (or possibly metallic) " atoms. " In this crystal, we can describe photons in terms of a band structure, as in the case of electrons. Of particular interest is a photonic crystal whose band structure possesses a complete pho-tonic band gap, a range of frequencies for which light is forbidden to propagate inside the crystal. Light is forbidden unless there is a defect in the otherwise perfect crystal. A defect can lead to localized photonic states in the gap, whose shapes and properties would be dictated by the defect's nature. Moreover, a significant and attractive difference between photonic crystals and electronic semiconductor crystals is the former's inherent ability to provide complete tunability. A defect in a photonic crystal could, in principle , be designed to be of any size, shape, or form and could be chosen to have any of a wide variety of dielectric constants. Thus, defect states in the gap could be tuned to any frequency and spatial extent of design interest. In addition to tuning the frequency, we also control the localized pho-tonic state's symmetry. All these capabilities provide a new dimension in our ability to mold or control the properties of light. In this sense, defects are good. And herein lies the exciting potential of photonic crystals. Photonic crystals let us manipulate light in ways never before possible. This article's purpose is to highlight some of these novel possibilities. Here, computation plays a particularly important role. Indeed, unlike electronic structure in semiconductors , photonic crystals are unique in that a computer can calculate phenomena described by Maxwell's equations to any desired degree of accuracy. Thus, computer …