Progress in Organic Coatings 99 (2016) 295–301 Contents lists available at ScienceDirect Progress in Organic Coatings j o ur na l ho me pa ge: www.elsevier.com/locate/porgcoat Fabrication of hydrophobic/hydrophilic switchable aluminum surface using poly(N-isopropylacrylamide) Heon-Yul Ryu a , Sung Ho Yoon c , Dong-Ho Han a , Hassan Hafeez b , Nagarjuna Reddy Paluvai b , Choon Soo Lee c , Jin-Goo Park a,b,∗ a Department of Bio-Nano Technology, Hanyang University, Ansan, Gyeonggi, 426-791, Republic of Korea b Department of Materials Engineering, Hanyang University, Ansan, Gyeonggi, 426-791, Republic of Korea c Automotive R&D Division, Hyundai Motor Group, Gyeonggi-do, Hwaseong, 445-706, Republic of Korea a r t i c l e i n f o Article history: Received 3 March 2016 Received in revised form 30 May 2016 Accepted 12 June 2016 Keywords: Poly(N-isopropylacrylamide) Thermosensitive hydrophobic/hydrophilic switchable surface Evaporator core Odor Air conditioning system a b s t r a c t 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. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Over the past decade, research has been carried out to mini- mize the odor that is generated in car air conditioner evaporators. Studies have shown that the production of this unpleasant odor is due to the condensation of moisture from the air in auto- mobile air-conditioning systems (ACS); this moisture provides a suitable environment to grow odor-causing micro-organisms [1–3]. These micro-organisms include a broad range of bacteria, protozoa and fungi, and especially, the methyl-obacterium and penicillium species, which can colonize various components within the AC parts and are the main source of malodor [4–6]. Com- pounds produced by these micro-organisms may be toxic and can have immunomodulating activity, which contributes to hyper allergenic responses or renders those exposed more susceptible to ∗ Corresponding author at: Department of Materials Engineering, Hanyang Uni- versity, Ansan, Gyeonggi, 426-791, Republic of Korea. E-mail address: jgpark@hanyang.ac.kr (J.-G. Park). other micro-organisms [7]. Numerous fungi are known to produce noxious volatiles, which can have adverse effects on the health of consumers [7,8]. Some commercial products are available in the market for treatment of malodors emanating from ACSs, but these products are recommended for repeated usage due to the recurrence of the problem. Replacing the evaporator and other components requires considerable expense and is inconvenient for the consumer. Few studies have been conducted to provide a per- manent solution for this problem. Therefore, a viable method for treating or preventing odors in automobile ACSs is required [9]. The evaporator core (evacore) is one of the most important parts of an automobile air conditioning system because it is where col- onization of such odor producing microorganisms can occur. It is made of a vast number of thin strips of aluminum. To prevent the growth of microorganisms, accumulation of condensed water on the surface must be inhibited. Various methods have been pro- posed such as drying the evacore after use or making its surface superhydrophobic [10,11]. When the surface is a super hydropho- bic in nature, the condensed water can be removed easily. In the present work, we hypothesized that the problem can be solved if http://dx.doi.org/10.1016/j.porgcoat.2016.06.008 0300-9440/© 2016 Elsevier B.V. All rights reserved.