New work work shows the state of the art of engineering in wearable display technology. Researchers have demonstrated a passive matrix quantum dot light-emitting diode (QLED) display fully integrated with flexible electronics. They realized the visualization of meaningful information such as images, recorded healthcare data, and other messages using their display. This ultrathin and ultrasoft QLED array can be conformally laminated on human skin.
In conventional liquid crystal displays (LCD), the liquid crystal (LC) material is contained in conventional LC cells, where the polyimide layers are used to align the LC homogeneously in the cell, and the transmissive indium tin oxide (ITO) electrodes are used to apply the electric field to reorient the LC along the field. Now, researchers have experimentally demonstrated that monolayer graphene films on the two glass substrates can function concurrently as the LC alignment layers and the transparent electrodes to fabricate an LC cell, without using the conventional polyimide and ITO substrates.
Many of the electronic devices we use in our daily life rely on liquid crystal display (LCD) technologies. LCDs get their name from the special liquid crystal solution that is contained between two thin glass plates inside the display. An electric field applied across the liquid crystal layer changes optical properties of the liquid crystals thus enabling their use in displays. A new paper reports several interesting size effects including monotonous and non-monotonous dependence of the total concentration of mobile ions in liquid crystals on the thickness of the cell and/or on the concentration of nanoparticles.
An recent analysis of the combined effect of nanoparticles and substrates on the concentration of mobile ions in liquid crystals considers both 100% pure and contaminated with ions substrates and nanoparticles. The results could be very useful for engineers trying to apply nanotechnology to liquid crystal devices. Specifically, the control of mobile ions in liquid crystals by means of nanoparticles and substrates of the cell tailored for specific applications - liquid crystal displays, light shutters, switches, modulators, etc.
Liquid crystals used in modern devices such as laptops, tablets and smartphones typically contain a small fraction of ionic contaminants. These ion contaminants can originate from multiple sources during the chemical synthesis of materials, in the process of assembling the device, and in its daily use.
In the case of LCDs, mobile ions in liquid crystals lead to such undesirable effects as image sticking, image flickering, and slow response. A promising solution to reduce the concentration of mobile ions in liquid crystal devices can be found by merging liquid crystals and nanotechnology.
Luminescent quantum dots (LQDs), which possess high photoluminescence quantum yields, flexible emission color controlling, and solution processibility, are promising for applications in lighting systems (warm white light without UV and infrared irradiation) and high quality displays. However, the commercialization of LQDs has been held back by the prohibitively high cost of their production. In a breakthrough approach, researchers have now succeeded in preparing highly emissive inorganic perovskite quantum dots at room temperature.
Compared to the conventional inefficient incandescent and fluorescent lighting technologies, LED light bulbs can, in principle, operate at an efficiency level of 100%. The current LED lighting technology, however, is not even close to reaching this limit. This is due to several problems which, however, can be by and large solved by employing tunnel junction integration into current nanowire LED structures. Demonstrating this, researchers have developed tunnel junction nanowire LEDs that can eliminate the use of resistive p-GaN contact layers, leading to reduced voltage loss and enhanced hole injection.
Polymer Dispersed Liquid Crystals (PDLCs) are micrometer-sized birefringent Liquid Crystal domains dispersed in an optically transparent continuous polymer matrix. The peculiarity of a PDLC system is that of scattering different amounts of an impinging light beam intensity, depending on the strength of an external electric field that is, eventually, applied to the system. A new generation of polymer-dispersed liquid crystals is based on a room temperature, polymerizable, nematic LC host.