Effect of TiO2 nanoparticles on contact line stick-slip behavior of volatile drops.

We describe an experimental investigation of the concomitant evaporation and (de)wetting behavior of sessile drops of ethanol, either pure, or containing small amounts of titanium oxide nanoparticles. Pure ethanol behaved in a more or less "ideal" manner, with constantly decreasing contact radius, at essentially constant contact angle. However, distinct "stick-slip" pinning behavior of the triple line occurred when nanoparticles were added to the base liquid. Increased nanoparticle concentration enhanced the "stick-slip" behavior. The observed behavior is attributed to the effects of particle accumulation near the contact line, caused by the now-established advective flow during evaporation. "Slip" behavior can be explained by hysteretic energy barriers, somewhat akin to line tension. The "stick" behavior was not complete: some triple line drift occurred ("pseudo-pinning"). It is postulated that this may be due to small-scale pinning of the triple line by deposited particles, or to increased effective viscosity due to high, local nanoparticle concentrations.

[1]  M. Shanahan.  Simple Theory of "Stick-Slip" Wetting Hysteresis , 1995 .

[2]  Ronald G. Larson,et al.  Evaporation of a Sessile Droplet on a Substrate , 2002 .

[3]  C. T. Nguyen,et al.  Temperature and particle-size dependent viscosity data for water-based nanofluids : Hysteresis phenomenon , 2007 .

[4]  Nagel,et al.  Contact line deposits in an evaporating drop , 2000, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[5]  K. Leong,et al.  Enhanced thermal conductivity of TiO2—water based nanofluids , 2005 .

[6]  D. Cahill,et al.  Nanofluids for thermal transport , 2005 .

[7]  W. Roetzel,et al.  Pool boiling characteristics of nano-fluids , 2003 .

[8]  J. Eastman,et al.  Enhanced thermal conductivity through the development of nanofluids , 1996 .

[9]  S. Kim,et al.  Surface wettability change during pool boiling of nanofluids and its effect on critical heat flux , 2007 .

[10]  M. Antoni,et al.  Evaporation and Marangoni driven convection in small heated water droplets. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[11]  Ping-Hei Chen,et al.  Effect of viscosity of base fluid on thermal conductivity of nanofluids , 2008 .

[12]  J. Eastman,et al.  Measuring Thermal Conductivity of Fluids Containing Oxide Nanoparticles , 1999 .

[13]  D. Vu,et al.  Wettability and the evaporation rates of fluids from solid surfaces , 1993 .

[14]  H. Masuda,et al.  ALTERATION OF THERMAL CONDUCTIVITY AND VISCOSITY OF LIQUID BY DISPERSING ULTRA-FINE PARTICLES. DISPERSION OF AL2O3, SIO2 AND TIO2 ULTRA-FINE PARTICLES , 1993 .

[15]  Kuniaki Nagayama,et al.  Stripe patterns formed on a glass surface during droplet evaporation , 1995 .

[16]  R. G. Picknett,et al.  The evaporation of sessile or pendant drops in still air , 1977 .

[17]  S. Herminghaus,et al.  Wetting: Statics and dynamics , 1997 .

[18]  J. Drelich.  The significance and magnitude of the line tension in three-phase (solid-liquid-fluid) systems , 1996 .

[19]  Khellil Sefiane,et al.  Experimental study of evaporating water-ethanol mixture sessile drop: influence of concentration , 2003 .

[20]  Khellil Sefiane,et al.  On the role of structural disjoining pressure and contact line pinning in critical heat flux enhancement during boiling of nanofluids , 2006 .

[21]  P. Gennes.  Wetting: statics and dynamics , 1985 .

[22]  J. Coninck,et al.  Evaporation of sessile liquid droplets , 2006 .

[23]  S. Betelú,et al.  Line tension approaching a first-order wetting transition: experimental results from contact angle measurements. , 2001, Physical review. E, Statistical, nonlinear, and soft matter physics.

[24]  Baldev Raj,et al.  Evidence for enhanced thermal conduction through percolating structures in nanofluids , 2008, Nanotechnology.

[25]  M. Shanahan,et al.  Kinetics of Triple Line Motion during Evaporation , 2008 .

[26]  Characteristic angles in the wetting of an angular region: deposit growth. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[27]  Martin E. R. Shanahan,et al.  Effects of evaporation on contact angles on polymer surfaces , 1994 .

[28]  T. Dupont,et al.  Capillary flow as the cause of ring stains from dried liquid drops , 1997, Nature.

[29]  Sarit K. Das,et al.  Survey on nucleate pool boiling of nanofluids: the effect of particle size relative to roughness , 2008 .

[30]  D. Das,et al.  Numerical study of turbulent flow and heat transfer characteristics of nanofluids considering variable properties , 2009 .

[31]  Haisheng Chen,et al.  Rheological behaviour of ethylene glycol based titania nanofluids , 2007 .

[32]  R. Larson,et al.  Marangoni effect reverses coffee-ring depositions. , 2006, The journal of physical chemistry. B.

[33]  Muzeyyen Dogan,et al.  Determination of diffusion coefficient-vapor pressure product of some liquids from hanging drop evaporation , 2000 .