TY - JOUR
T1 - Turning a superhydrophilic surface weakly hydrophilic
T2 - Topological wetting states
AU - Gao, Yurui
AU - Zhu, Chongqin
AU - Zuhlke, Craig
AU - Alexander, Dennis
AU - Francisco, Joseph S.
AU - Zeng, Xiao Cheng
N1 - Funding Information:
This work was supported by the Nebraska Center for Energy Sciences Research at University of Nebraska-Lincoln and by UNL Holland Computing Center. J.S.F. and X.C.Z. were supported by NSF grant CHE-1665324.
Funding Information:
This work was supported by the Nebraska Center for Energy Sciences Research at University of Nebraska–Lincoln and by UNL Holland Computing Center. J.S.F. and X.C.Z. were supported by NSF grant CHE-1665324.
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/10/28
Y1 - 2020/10/28
N2 - For water droplets placed on a rough or structured surface, two distinct wetting states commonly observed are either the Wenzel state (droplets wet the surface without showing air pockets beneath the droplets) or the Cassie state (droplets reside on top of the structure with air pockets trapped beneath the droplets). Herein, we show molecular dynamics (MD) simulation evidence of a previously unreported wetting behavior, i.e., the rise of multiple Wenzel states on the structured surfaces whose flat-surface counterparts are superhydrophilic (i.e., complete wetting surfaces with the hallmark of zero contact angle for water droplets). Specifically, our MD simulations show that on the structured surfaces with topology of closed-loop nanowalls/ nanochannels, the water droplet can exhibit multiple Wenzel wetting states with the apparent contact angles >0°. We name these distinct multiple Wenzel states as "topological wetting states"because their existence can be attributed to the topology of the closedloop nanowalls/nanochannels. Regardless of the shape of the closed loops, such topological wetting states can always arise due to the topological invariant (i.e., all closed loops entail the same topological genus value). This unusual wetting behavior is contrary to the conventional view (and to the prediction of the Wenzel equation), namely, a rough hydrophilic surface should have stronger hydrophilicity than its flat-surface counterpart.
AB - For water droplets placed on a rough or structured surface, two distinct wetting states commonly observed are either the Wenzel state (droplets wet the surface without showing air pockets beneath the droplets) or the Cassie state (droplets reside on top of the structure with air pockets trapped beneath the droplets). Herein, we show molecular dynamics (MD) simulation evidence of a previously unreported wetting behavior, i.e., the rise of multiple Wenzel states on the structured surfaces whose flat-surface counterparts are superhydrophilic (i.e., complete wetting surfaces with the hallmark of zero contact angle for water droplets). Specifically, our MD simulations show that on the structured surfaces with topology of closed-loop nanowalls/ nanochannels, the water droplet can exhibit multiple Wenzel wetting states with the apparent contact angles >0°. We name these distinct multiple Wenzel states as "topological wetting states"because their existence can be attributed to the topology of the closedloop nanowalls/nanochannels. Regardless of the shape of the closed loops, such topological wetting states can always arise due to the topological invariant (i.e., all closed loops entail the same topological genus value). This unusual wetting behavior is contrary to the conventional view (and to the prediction of the Wenzel equation), namely, a rough hydrophilic surface should have stronger hydrophilicity than its flat-surface counterpart.
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U2 - 10.1021/jacs.0c07224
DO - 10.1021/jacs.0c07224
M3 - Article
C2 - 33059449
AN - SCOPUS:85094933458
VL - 142
SP - 18491
EP - 18502
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 43
ER -