from nonlinearities in the advective momentum transport ([@cox1968; @ho1974; @vas1976; @vas1977; @cox1977; @mcl1993; @che1994; @bec1996; @mag2003]) and/or the interfacial deformability ([@cha1965; @cha1979; @sha1988; @uij1993; @uij1995; @mag2003; @wan2006]), to break the symmetry.

For a tank-treading vesicle translating parallel to the wall, the migration force was theoretically obtained by [@oll1997], in which the vesicle shape is prescribed as a strongly non-spherical ellipsoid, and the theory was experimentally validated by [@cal2008]. For a bubble or drop, the shape cannot be prescribed since it obeys the Laplace law and depends on the surrounding fluid flow. The theoretical success in solving the nontrivial problem of the deformation-induced migration of the bubble or drop was made by [@mag2003] using the Faxén mirror image technique and the Lorentz reciprocal theorem. However, [@wan2006] performed a numerical study on the motion of a drop with the same viscosity as the surrounding fluid in a linear shear flow by means of a boundary element method, and pointed out that the theory considerably underestimates the migration velocity or erroneously predicts the lateral motion, despite consistent predictions of the rising velocity and the interfacial deformation. Recently, [@tak2009] experimentally measured the lateral migration velocity of slightly deformed bubbles in a wall-bounded shear flow, 