Abstract:

Self-assembly of tobacco mosaic virus(TMV) particles by drying TMV buffered solution constrained in a capillary tube, between two parallel glass slides and in a cylinder-on-flat geometry were studied, respectively. Optical microscopy(OM) and atomic force microscopy(AFM) were employed to characterize the patterns produced. Effect of the concentration of TMV on patterns was also explored. The results show that highly ordered structures could be fabricated under these three confined conditions which were attributed to the periodical, repetitive “stick-slip” motion of the contact line. Stripes parallel to the contact line but perpendicular to the long axis of the capillary tube were formed in a glass capillary tube after evaporation. As the solution front moved inward, both l(span of a stripe) and w(width of a stripe) gradually increased. When drying TMV buffered solution trapped between two glass slides, patterns in a tetramerous radial symmetry were produced. From each side of the slide, both l and w increased as stripes approached the longitudinal axis to the center. Parallel gradient straight stripes were obtained when TMV buffered solution was allowed to evaporate from a cylinder-on-flat geometry. As the contact line propagated from the capillary edge toward the cylinder/Si contact center, both l and w decreased. The values of l for the outermost, middle and innermost regions are 28.4, 20.9 and 8.4 μm, respectively. While the values of w are 17.5, 9.2 and 0.8 μm, correspondingly. Moreover, the height of the stripe decreased from 33.9 nm to 30.4 nm, finally to 29.5 nm. In all patterns formed under these three kinds of confinement conditions, individual TMV particles aligned parallel to the contact line, which could not only relieve the strong dipole-dipole repulsion between TMV particles, but also effectively minimize the interfacial energy. Concentration of TMV had the same effect on patterns under these three confinements:both l and w increased with the increase of concentration until no stripe patterns were observed and continuous films of TMV were formed.

Key words: confined evaporation, tobacco mosaic virus (TMV), self-assembly