2013年11月21日 Nature

nero1981

2013年11月21日 Nature: Z  p' W, M  S1 E. S1 o

9 ?! j8 L4 j$ N( d3 e; A% N' d# L: ]A water drop strikes the water-averse wing of a Morpho 5 u. }$ Q0 P  e2 }  @4 ?# y$ [
butterfly. There are many uses for surfaces that can stay dry, self-clean or
0 l+ v1 R) c$ i5 B" q2 bresist icing. Liquid drops hitting such surfaces tend to spread out and then   p6 W, c& y9 d1 I) E2 E3 r& |3 f0 A
retract before finally bouncing. Many applications benefit from minimizing the . N6 }1 f* w- Y! M( r
contact time between drop and surface, which is generally assumed to occur if
* Y- F! g/ U7 A# bthe impacting drop deforms symmetrically. Kripa K. Varanasi and colleagues now % i) c/ [2 y" R! D; j
show that drops bounce off faster from a superhydrophobic surface with a 8 u0 J) D  v/ J  m' ~( U' O) c9 R
morphology that redistributes the liquid mass so that it no longer spreads and * ~' V$ Y% A' u  H5 ~* E0 p5 g8 ^
retracts symmetrically. Theory and experiments confirm that this strategy
0 ]+ l5 r0 x% B) W* Xshortens the contact time between a bouncing drop and a surface beyond what was / {, R8 Q0 c8 [% w* ~
thought possible. Photo: A. T. Paxson, K. Hounsell, J. W. Bales, J. C. Bird ) m) H; n$ |, t2 h$ O
& K. Varanasi.' w1 Y* {- d* Y" G3 v4 ]6 n& _* E9 C
4 R3 P% c- \2 E$ d7 t

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