Electric-field-induced capillary attraction between like-charged particles at liquid interfaces

Nanometre- and micrometre-sized charged particles at aqueous interfaces are typically stabilized by a repulsive Coulomb interaction. If one of the phases forming the interface is a nonpolar substance (such as air or oil) that cannot sustain a charge, the particles will exhibit long-ranged dipolar repulsion; if the interface area is confined, mutual repulsion between the particles can induce ordering and even crystallization. However, particle ordering has also been observed in the absence of area confinement, suggesting that like-charged particles at interfaces can also experience attractive interactions. Interface deformations are known to cause capillary forces that attract neighbouring particles to each other, but a satisfying explanation for the origin of such distortions remains outstanding. Here we present quantitative measurements of attractive interactions between colloidal particles at an oil–water interface and show that the attraction can be explained by capillary forces that arise from a distortion of the interface shape that is due to electrostatic stresses caused by the particles' dipolar field. This explanation, which is consistent with all reports on interfacial particle ordering so far, also suggests that the attractive interactions might be controllable: by tuning the polarity of one of the interfacial fluids, it should be possible to adjust the electrostatic stresses of the system and hence the interparticle attractions.

[1]  Onoda,et al.  Direct observation of two-dimensional, dynamic clustering and ordering with colloids. , 1985, Physical review letters.

[2]  A. Hurd The electrostatic interaction between interfacial colloidal particles , 1985 .

[3]  Fluctuation-induced interactions between rods on a membrane. , 1996, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[4]  C. P. Bean Magnetization of hard superconductors , 1962 .

[5]  P. Pusey,et al.  Phase behaviour of concentrated suspensions of nearly hard colloidal spheres , 1986, Nature.

[6]  J. Korley,et al.  Colloid crystal self-organization and dynamics at the air/water interface , 1998, Nature.

[7]  F. Martínez-López,et al.  Probing interaction forces in colloidal monolayers: Inversion of structural data , 2001 .

[8]  D. Grier,et al.  Methods of Digital Video Microscopy for Colloidal Studies , 1996 .

[9]  Mark Goulian,et al.  Long-Range Forces in Heterogeneous Fluid Membranes , 1993 .

[10]  D. Johannsmann,et al.  Long-range attraction between colloidal spheres at the air-water interface: the consequence of an irregular meniscus , 2000, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[11]  K. Nagayama,et al.  Capillary interactions between particles bound to interfaces, liquid films and biomembranes. , 2000, Advances in colloid and interface science.

[12]  D. A. Saville,et al.  Colloidal Dispersions: ACKNOWLEDGEMENTS , 1989 .

[13]  David C. Morse,et al.  Droplet Elasticity in Weakly Compressed Emulsions , 1993 .

[14]  Clogston Upper limit for the critical field in hard superconductors. [V/sub 2. 95/Ga, NbâSn,VâSi, V/sub 1. 95/ Ga] , 1962 .

[15]  J. E. Evetts,et al.  Flux vortices and transport currents in type II superconductors , 2001 .

[16]  S. Botchway,et al.  Measurement of long-range repulsive forces between charged particles at an oil-water interface. , 2002, Physical review letters.

[17]  I. B. Ivanov,et al.  Two-dimensional crystallization , 1993, Nature.

[18]  J. Ruíz-García,et al.  Formation of two-dimensional colloidal voids, soap froths, and clusters , 1998 .

[19]  K. Nagayama,et al.  Capillary meniscus interaction between colloidal particles attached to a liquid-fluid interface , 1992 .

[20]  G. Whitesides,et al.  Self-Assembly of Mesoscale Objects into Ordered Two-Dimensional Arrays , 1997, Science.

[21]  P. Pieranski,et al.  Two-Dimensional Interfacial Colloidal Crystals , 1980 .

[22]  Lee R. White,et al.  The interaction of colloidal particles collected at fluid interfaces , 1981 .

[23]  P. Kralchevsky,et al.  Capillary forces and structuring in layers of colloid particles , 2001 .