In this study, the behaviors of water droplets on superhydrophobic polyester (PET) films as well as on woven and knitted fabrics with different surface microstructures were analyzed. The water droplet volume, height of release (h), and surface inclination were modified to study the dynamic behavior of water droplets using a pressure balance and the Weber number (We). The droplet volume did not affect the static contact angle. However, the shedding and sliding angles decreased with an increase in droplet volume. The water droplets rebounded on the surface of the superhydrophobic PET films with nano-roughness regardless of the surface inclination angle or h. However, the water droplets with h = 10 cm were pinned on the horizontal surfaces of the woven and knitted fabrics with micro-sized pores, where the dynamic pressure (Pd) exceeded the capillary pressure. On an inclined surface, the water droplets rebounded on the surface of the woven fabric, owing to a decrease in Pd and an increase in the surface inclination angle. However, on the surface of the knitted fabric, pinning was observed even when the surface was tilted, regardless of the inclination angle. The sliding velocity of the droplets after rebound decreased in the following order: film, knitted fabric, woven fabric. With an increase in the inclination angle of the surface and the droplet volume, the sliding velocity increased, which was accompanied by a decrease in vertical impact velocity (V) and an increase in the gravitational force. In terms of We, the droplets with a low We rebounded on all superhydrophobic surfaces, whereas the droplets with a high We were pinned on the surface of the woven and knitted fabrics.
GaoXJiangL.Water-repellent legs of water striders. Nature2004;
432: 36.
3.
NurajeNKhanWSLeiY, et al.
Superhydrophobic electrospun nanofibers. J Mater Chem A2013;
1: 1929–1946.
4.
ShimMHKimJParkCH.The effects of surface energy and roughness on the hydrophobicity of woven fabrics. Text Res J2014;
84: 1268–1278.
5.
XueCHChenJYinW, et al.
Superhydrophobic conductive textiles with antibacterial property by coating fibers with silver nanoparticles. Appl Surf Sci2012;
258: 2468–2472.
6.
KimJKimHParkCH.Contribution of surface energy and roughness to the wettability of polyamide 6 and polypropylene film in the plasma-induced process. Text Res J2016;
86: 461–471.
7.
HanMSParkYParkCH.Development of superhydrophobic polyester fabrics using alkaline hydrolysis and coating with fluorinated polymers. Fibers Polym2016;
17: 241–247.
8.
XueCHBaiXJiaST, et al.
Fluorine based superhydrophobic coatings.Sci Rep2016;
6: 27262; Appl Sci 2012; 2: 453-464.
9.
OhJHParkCH.Robust fluorine‐free superhydrophobic PET fabric using alkaline hydrolysis and thermal hydrophobic aging process. Macromol Mater Eng2018;
303: 1700673.
10.
ChenLXiaoZChanPCH, et al.
A comparative study of droplet impact dynamics on a dual-scaled superhydrophobic surface and lotus leaf. Appl Surf Sci2011;
257: 8857–8863.
11.
KimHKimSH.Nonwettable hierarchical structure effect on droplet impact and spreading dynamics. Langmuir2018;
34: 5480–5486.
12.
LiZGuoZ.Bioinspired surfaces with wettability for antifouling application. Nanoscale2019;
11: 22636–22663.
13.
ParkSKimJParkCH.Superhydrophobic textiles: review of theoretical definitions, fabrication and functional evaluation. J Eng Fiber Fabr2015;
10: 155892501501000.
14.
MiwaMNakajimaAFujishimaA, et al.
Effects of the surface roughness on sliding angles of water droplets on superhydrophobic surfaces. Langmuir2000;
16: 5754–5760.
15.
ZimmermannJSeegerSReiflerFA.Water shedding angle: a new technique to evaluate the water-repellent properties of superhydrophobic surfaces. Text Res J2009;
79: 1565–1570.
16.
KongQZhangZLiZ, et al.
Dynamic hydrophobic behavior of water droplets impact on the cotton fabrics coated with POSS block copolymer. Cellulose2019;
27: 1705–1716.
17.
BirdJCDhimanRKwonH-M, et al.
Reducing the contact time of a bouncing drop. Nature2013;
503: 385–388.
18.
KimSYOhJHParkCH.Development of energy-efficient superhydrophobic polypropylene fabric by oxygen plasma etching and thermal aging. Polymers2020;
12: 2756.
19.
BartoloDBouamrireneFVerneuilÉ, et al.
Bouncing or sticky droplets: Impalement transitions on superhydrophobic micropatterned surfaces. Europhys Lett2006;
74: 299–305.
20.
AntoniniCVillaFMarengoM.Oblique impacts of water drops onto hydrophobic and superhydrophobic surfaces: outcomes, timing, and rebound maps. Exp Fluids2014;
55: 1713.
21.
YeongYHBurtonJLothE, et al.
Drop impact and rebound dynamics on an inclined superhydrophobic surface. Langmuir2014;
30: 12027–12038.
22.
KimHOhJ-HHee ParkC.Superhydrophobic fabric mixed with polyester and cotton yarns modified by alkaline treatment and thermal aging. Text Res J2020;
91: 1274–1289.
23.
XingZJuZZhaoY, et al.
One-pot hydrothermal synthesis of nitrogen-doped graphene as high-performance anode materials for lithium ion batteries.Sci Rep2016:
6: 26146.
24.
HaworthBDongZWDavidsonP.Characterisation of shrinkage in oriented PET films and containers by thermomechanical analysis (TMA). Polym Int1993;
32: 325–335.
25.
GohilRM.Morphology‐property relationships in oriented PET films: a role of in‐plane crystalline orientation distribution on the film properties. J Appl Polym Sci1993;
48: 1635–1648.
26.
CansoyCE.The effect of drop size on contact angle measurements of superhydrophobic surfaces. RSC Adv2014;
4: 1197–1203.
27.
HassanGYilbasBSAl-SharafiA, et al.
Self-cleaning of a hydrophobic surface by a rolling water droplet. Sci Rep2019;
9: 5744–5744.
28.
XueCHBaiXJiaST.Robust, self-healing superhydrophobic fabrics prepared by one-step coating of PDMS and octadecylamine.Sci Rep2016:
6: 27262.
29.
JonasAMCaiRVermeyenR, et al.
How roughness controls the water repellency of woven fabrics. Mater Des2020;
187: 108389.
30.
PierceECarmonaFJAmirfazliA.Understanding of sliding and contact angle results in tilted plate experiments. Colloid Surf A2008;
323: 73–82.
31.
LvCYangCHaoP, et al.
Sliding of water droplets on microstructured hydrophobic surfaces. Langmuir2010;
26: 8704–8708.
32.
YilbasBSAl-SharafiAAAliH, et al.
Dynamics of a water droplet on a hydrophobic inclined surface: Influence of droplet size and surface inclination angle on droplet rolling. RSC Adv2017;
7: 48806–48818.
33.
SakaiMKonoHNakajimaA, et al.
Sliding of water droplets on the superhydrophobic surface with ZnO nanorods.Langmuir2009;
25: 14182–14186.
34.
TenjimbayashiMSamitsuSNaitoM.Simultaneous detection and repair of wetting defects in superhydrophobic coatings via Cassie–Wenzel transitions of liquid marbles. Adv Funct Mater2019;
29: 1900688.
35.
ButtHJGaoNPapadopoulosP, et al.
Energy dissipation of moving drops on superhydrophobic and superoleophobic surfaces. Langmuir2017;
33: 107–116.
36.
DengTVaranasiKKHsuM, et al.
Nonwetting of impinging droplets on textured surfaces. Appl Phys Lett2009;
94; 133109.
37.
LeeDJKimHMSongYS, et al.
Water droplet bouncing and superhydrophobicity induced by multiscale hierarchical nanostructures. ACS Nano2012;
6: 7656–7664.
MurugadossKDharPDasSK.Role and significance of wetting pressures during droplet impact on structured superhydrophobic surfaces. Eur Phys J E Soft Matter2017;
40: 1.
40.
TsaiPPachecoSPiratC, et al.
Drop impact upon micro- and nanostructured superhydrophobic surfaces. Langmuir2009;
25: 12293–12298.
41.
LeClearSLeClearJAbhiijeet, et al.
Drop impact on inclined superhydrophobic surfaces. J Colloid Interface Sci2016;
461: 114–121.
42.
GhapanvariSKhoddamiAHasaniH.Effect of weft knitted polyester fabric structure on its hydrophobicity after fluorocarbon finishing. Text Light Ind Sci Technol2015;
4: 27–34.
43.
AbdelmagidGYilbasBSAl-SharafiA, et al.
Water droplet on inclined dusty hydrophobic surface: Influence of droplet volume on environmental dust particles removal. RSC Adv2019;
9: 3582–3596.
44.
AhmedGSellierMJermyM, et al.
Modeling the effects of contact angle hysteresis on the sliding of droplets down inclined surfaces. Eur J Mech B Fluids2014;
48: 218–230.
45.
HyväluomaJKoponenARaiskinmäkiP, et al.
Droplets on inclined rough surfaces. Eur Phys J E2007;
23: 289–293.
46.
BarberoglouMZorbaVPagozidisA, et al.
Electrowetting properties of micro/nanostructured black silicon. Langmuir2010;
26: 13007–13014.
