Smart Window by Using Charged Nanoparticles Dispersed in the Pyramid Patterns

In modern society, energy issues are the most important issues, and according to a 2020 report by the International Energy Agency (IEA), energy used in buildings accounts for 35% of energy consumption used in industry. Accordingly, research and technology development aimed at reducing energy consumption are required. To solve this problem, a technology called smart windows is in the spotlight. A smart window refers to a window in which the transmittance can be adjusted according to light, temperature, and user preference. Electrical control methods are the most commercially available technologies among smart window driving methods, and typically include electrochromic (EC), suspended particle device (SPD), and polymer dispersion liquid crystal (PDLC).<br/><br/>These technologies are not only applicable to transparent display devices, but also have proven their commercialization potential. However, electrochromic (EC) has the disadvantages of high manufacturing cost and long time required for discoloration, and SPD has low manufacturing cost, but has a high driving voltage, which causes a problem of deteriorating durability due to condensation and deterioration. In addition, PDLC has a problem of a viewing angle without Haze due to a change in the refractive index of the liquid crystal in a transparent state. Technical research is needed to solve these problems.<br/><br/>Recently, display research using the transmittance change mechanism of cephalopods such as squid is being conducted. Squid has a pigment pocket in which pigment pigments are dispersed, and the size of the pigment pocket is controlled with muscles to change transmittance. However, in the case of transparent display research based on the pigment bag of squid, there is a disadvantage that commercialization is difficult because it uses magnetic fields.<br/><br/>In this study, in order to solve the above problems, a device was devised to control the transmittance by forming a pyramid pattern and dispersing charged nanoparticles within the pattern to move particles by electric force. The charged nanoparticle was used by dielectrophoresis. The irregular electric field required for the movement of charged nanoparticle by dielectrophoresis was used with a pyramid structure with an asymmetric structure. A method was introduced to control the light absorption area by dispersing charged nanoparticle in the micro pyramid pattern and applying an AC voltage to ITO-coated glass by dielectrophoresis. By making a pyramid pattern made of a polymer material having the same refractive index as that of charged nanoparticle, light was prevented from being refracted by the pyramid structure. In addition, it was verified whether ON/OFF switching is possible to check the behavior of charged nanoparticle in the pyramid pattern and measure the change in transmittance over time.