Research Proposal on Thermosensitive PAH in Active Smart Window Design
Introduction
During a cold night, it would be highly favorable if a window could automatically turn into the opaque color in order to retain heat. Currently, “Adaptive infrared-reflecting systems” have already been made possible to statically reflect and regulate the infra-red radiation(Xu, Stiubianu&Gorodetsky, 2018). It is inspired by cephalopods. The research motivation is to shift the reflection peak line to the visible line region. Currently, researchers have focused on using a combination of Vanadium dioxide VO2 and PNIPAAm as they could rapid respond to heat changes and considerable good light absorption, scattering and transmission properties. However, if the smart window is made in PNIPAAm, the quality of the window is very problematic(La et al, 2017). PNIPAAm is brittle in nature. It also has rather poor stretchability. In this context, it seems that Polyampholyte hydrogels (PAH) would be more referable as it is not brittle in nature(Kim et al, 2018).
Literature Review
Interior Glass, Exterior Glass and Rear Projection
Currently, the smart window may have different kinds, including the interior glass, exterior glass, and rear projection. The Interior glass controls the amount of heat and visible light that enters a space either manually or automatically. It could instantaneously turn the glass from transparent into opaque color. It could also create privacy by blocking visible light and so on. Exterior glass could provide privacy without the need for curtains and blinds. It is usually used for UV protection or reflecting Infrared. It could also provide over 40% solar reduction. Rear project is designed for home theater or corporate display purpose. The smart glass or window technological could be applied in corporate office building, residential areas, heath-care facilities and so on.
Active and Passive Smart Window
There are also two different groups. One is called active smart window. The other one is called passive smart glass. The passive photochromic and thermochromic in nature. On the other hand, the active smart window have three categories, namely electrochromic, liquid crystal (PDLC) and suspended particle Device (SPD). In fact, all researches on the smart window technology development falls in these realms. Passive Smart Glass is more sensitive and responsive to non-electrical stimulus such as Heat, Infrared, UV radiation and so on. In other words, it could not be manually controlled. Active Smart glass, on the other hand, could respond to electric stimulus very well. It could be controlled manually or automatically.
Electrochromic smart glass is often applied on the exterior glass as the aforementioned. The visible light transmission in the darkness state could be less than 3%. however, it could still be seen through(Piccolo&Simone,2015). There is quite a limited privacy. the Electrhochromic smart glass is comprised of two glass panels with several layers incorporated in between. It works through passing low-voltage electric charges across the conductive coating on the glass surface. It thus activates the electrochromic layer so that the color would changed from clear to dark. As this type of smart window is responsive to electric stimulus, the electric current could be activated manually or automatically by sensors which are sensitive to light intensity. One advantage of the electrochromic smart window is that it only needs electricity to charge its opacity. It does not have to maintain a specific shade. The switching speed of the electrochromic glass is rather slow. Usually, the larger the glass panel, the slower the switching speed. Very often, the consistencies of tint changes may also vary from one smart glass to another. It is also called “Iris effect”. Large glass panel often has this effect at the glazing’s outer edges.
Suspended Particle Device(SPD) is another kind of active smart window. SPD is usually a film illuminating nano-scale rod-like particles which are suspended in liquid between two pieces of glasses or attached to one layer(Ghosh, Norton&Duffy, 2016). When there is not potential difference, the suspended particles are randomly organized. It will block or absorb the light. When the electric power is applied, the position of the suspended particles would aligned so that the light could pass through. Through varying the voltages applied on the two glass panels, the amount of visible light could be thus regulated manually. Actually, the SPD works faster than the electrochromic smart window. The visible light transmission of SPD is around 0.5%. The entire process would take less than 5 seconds.
Polymer Dispersed Liquid Crystal (PDLC) is also another type of active smart window. The basic idea of PDLC is using the micro droplets of liquid crystals encapsulated in a polymer matrix(Mochizuki, Omi, Takigami, Kondo&Okuzaki, 2016). Without applying voltage, the micro droplets would be randomly organized. It will refract the lights which enter the mixture. It will result the smart window in opaque color. When electricity is applied, the electrons would be lined up according to the direction of electric field. It will allow the light passing through. The smart window would turn to transparent color. When the electricity is suddenly removed, the droplets would be in their random configuration again. As such, the light is scattered heavily. It would pass the window directly. It could an image-blocking effect.
Methodology
In this research, the major purpose is to fabricate a active array of visible light-sensitive smart window. In other words, the visible light should be regulated and controlled manually. The product should be an active smart window instead of a passive one.
First, it would be necessary to prepare the PAH samples very carefully. The method of copolymerization method is often employed by researchers to prepare PAHs. The necessary materials include NaSS, MPTC, DMAEA-Q, MBAA, and photo-initiator. All these materials could be purchased from Sigma-Aldrich. The aqueous solution could be prepared by injecting the above-mentioned materials into a cell comprising of two glass plates by a Teflon spacer.
The PAH sample could be characterized by a custom-made laser measurement system. The constant visible light source could be provided by the laser diode in the system. Two photodiodes would be connected to the data acquisition device. The two photodiodes are installed at 0 and 75 degrees in order to receive transmitted and scattered lights. The test temperature would be kept at 25 degrees or the room temperature. The Visible light transmittance would be measured by a NIR-UV spectrophotometer. IR on the other hand is often measured by Fourier transform infrared spectrophotometer. However, as the research focus is on visible light spectra. FTIR would not be relevant. The water content of PAH would be calculated through the mass difference of pristine samples and dried samples.
The active smart window would be applied direct current. The applied current would be measured and recorded accordingly. Smartphone would be used to record the optic image of the smart window. It will also record how the amount of lights that enter the window might change with the changes of voltages. After conducting this experiment, it is expected that whether the optic properties of PAH is good enough to regulate the lights in visible light spectra.
Anticipated Outcome
If the new smart window is successfully developed, it is expected that many people could benefit from this new smart glass technology. Smart window could have the ability to control the amount of visible light and even heat passing through. For instance, the glass could change from transparent to completely opaque. During the winder time, it could retain more heat for people who reside or work in a building. It could also be controlled or regulated through a smart phone app. In other words, through accessing the light-controlling app, the smart window could be responding to light or heat changes very accurately. One major advantage is that the new smart window could partially blocking the light while maintaining a view of outside scenes. The current technological frontiers in the active Smart window design may include electrochromic, photochromic, suspended particle, and liquid crystal device technologies. More or less, the current technologies in reflecting or filtering visible lights are the same. The most critical part is certainly the selection of appropriate materials. After conducting this research, it is believed that PAH would be a prior choice in the real world application. The feasibility of commercializing the smart window is also very high.
In the future, the research focus should be on measuring the thermal properties of PAH in the active smart window design. From this research, it is feasible for us to learn about how good the PAH is in controlling the visible light. However, it will also be beneficial if the PAH could have significant solar reduction. If the solar reduction is high, the new active smart window could be installed in tropical regions.
Reference
Ghosh, A., Norton, B., & Duffy, A. (2016). Daylighting performance and glare calculation of a suspended particle device switchable glazing. Solar Energy, 132, 114-128.
Kim, G. W., Lampande, R., Choe, D. C., Ko, I. J., Park, J. H., Pode, R., & Kwon, J. H. (2018). Next generation smart window display using transparent organic display and light blocking screen. Optics express, 26(7), 8493-8502.
La, T. G., Li, X., Kumar, A., Fu, Y., Yang, S., & Chung, H. J. (2017). Highly Flexible, Multipixelated Thermosensitive Smart Windows Made of Tough Hydrogels. ACS applied materials & interfaces, 9(38), 33100-33106.
Mochizuki, T., Omi, T., Takigami, Y., Kondo, T., & Okuzaki, H. (2016). Fabrication of Transparent Electrodes Using PEDOT/PSS and Application to a Polymer Dispersed Liquid Crystal Display. Kobunshi Ronbunshu, 73(1), 96-101.
Piccolo, A., & Simone, F. (2015). Performance requirements for electrochromic smart window. Journal of Building Engineering, 3, 94-103.
Xu, C., Stiubianu, G. T., & Gorodetsky, A. A. (2018). Adaptive infrared-reflecting systems inspired by cephalopods.Science, 359(6383), 1495-1500.