Fabrication of hydrophobic/hydrophilic switchable aluminum surface using poly( N -isopropylacrylamide)

Abstract

Abstract The quick removal of condensed water generated during operation of an automobile air conditioner is essential to prevent the growth of bacteria and fungi, which may produce odors and cause illness. Modification of an evaporator core (evacore) surface to provide superhydrophobicity is one technique that can be used to remove the condensed water. However, if the evacore surface is superhydrophobic, small water droplets can flow towards the inside of the automobile engine along with the air flowing through the air conditioner. In the present investigation, we propose an approach to fabricate an evacore surface that can be switched from hydrophobic to hydrophilic by changing the temperature. In the initial stage of air conditioner operation, the surface is hydrophilic at ambient temperature, causing water to stay on the surface. After the operation of the air conditioner, the surface becomes hydrophobic at a higher temperature, and the water rolls off the surface. To fabricate this surface, aluminum (Al) substrate was used, and it was etched by immersion in 10 wt.% hydrochloric acid (HCl) for 8 min. The etched Al substrate was coated with a functionalized poly(NIPAM- co -MAA) polymer by immersing in a coating solution for 1 h at 120 °C. The resulting surface is a thermosensitive hydrophobic/hydrophilic switchable Al surface, which provides a hydrophilic state under the lower critical solution temperature (LCST), 35 °C, and a hydrophobic state above the LCST.