Window Screen

Particulate matter (PM) is a matter of serious concern due to its enormous threat to public health, especially in developing countries like India and China. Moreover, its extremely high concentration in air badly affects visibility, ecosystems, direct sunlight, and climate forcing. It is mainly classified into two types on the basis of size as PM2.5 and PM10. PM2.5 is particularly hazardous due to its extremely small size, which can easily penetrate into human lungs and bronchi. Frequent exposure to such polluted weather conditions can cause harmful health issues like stroke, cancer, heart failure, and lung infections, and short-term exposure to an over polluted PM environment can create a serious risk of asthmatic problems. Nowadays, a large number of industries working with fossil fuels in many developing countries like China are responsible for creating such high PM pollution. On extremely hazy days, visibility is decreased significantly and becomes even worse at night. Personally, people resolve this problem by using respiratory face mask as protective tools during outdoor activities. In the case of indoor commercial buildings, protection is usually provided by complex ventilation system. In contrast, common residential buildings are seldom equipped with such PM filtering systems. Additionally, huge amount of energy is always required for ventilation system performance.
Quality and exchange of indoor air is also a matter of great concern while people are staying indoors. It would be perfect if passive air exchange could be accomplished through natural ventilation of window screen for indoor air filtration. Windows with high surface area always facilitate efficient air exchange for indoor purposes. The idea of coating a window screen with a suitable nanofibrous layer owing to not only capture high amounts of PM but that is also highly transparent to the sunlight and sight viewing at the same moment would be of greater interest. Researchers found that polar polymeric nanofiber membranes like polyacrylonitrile (PAN), polyamide, and polyimide have much higher PM removal efficiency as compared to that of nonpolar polypropylene fibers that are used in existing filtration membranes. The high capture ability of the polar polymeric nanofiber membrane makes it possible to use a thin nanofiber layer on a window screen, which can be highly transparent and low air flow resistant. Therefore, coating a thin layer of electrospun nanofibers on the window screen improves the indoor air quality and it is applicable in houses, hospitals and offices. The following bar chart makes a comparison between FNM’s nanofiber coated window screen and other types of window screen in the market (for 0.4, 1 and 2.5 µm particles size). As it is shown, FNM’s coated window screen has much higher efficiency and it does not have a significant increase of pressure drop compared to the other coated window screen.

References
1. Khalid, Bilal, Xiaopeng Bai, Hehe Wei, Ya Huang, Hui Wu, and Yi Cui. "Direct blow-spinning of nanofibers on a window screen for highly efficient PM2.5 removal." Nano letters 17, no. 2 (2017): 1140-1148.
2. Liu, Chong, Po-Chun Hsu, Hyun-Wook Lee, Meng Ye, Guangyuan Zheng, Nian Liu, Weiyang Li, and Yi Cui. "Transparent air filter for high-efficiency PM2.5 capture." Nature communications 6 (2015): 6205.