It is usually believed that wall slip contributes small effects to macroscopic flow characteristics. Here we demonstrate that this is not the case for the thermocapillary migration of a long bubble in a slippery tube. We show that a fraction of the wall slip, with the slip length λ much smaller than the tube radius R, can make the bubble migrate much faster than without wall slip. This speedup effect occurs in the strongslip regime where the film thickness b is smaller than λ when the Marangoni number S = τ T R/σ 0 ( 1) is below the critical value S * ∼ (λ/R) 1/2 , where τ T is the driving thermal stress and σ 0 is the surface tension. The resulting bubble migration speed is found to be U b ∼ (σ 0 /µ)S 3 (λ/R), which can be more than a hundred times faster than the no-slip result U b ∼ (σ 0 /µ)S 5 (Wilson,

Against the common wisdom that wall slip plays only a minor role in global flow characteristics, here we demonstrate theoretically for the displacement of a long bubble in a slippery channel that the well-known Bretherton 2/3 law can break down due to a fraction of wall slip with the slip length λ much smaller than the channel depth R. This breakdown occurs when the film thickness h ∞ is smaller than λ, corresponding to the capillary number Ca below the critical value Ca * ∼ (λ/R) 3/2 . In this strong slip regime, a new quadratic law h ∞ /R ∼ Ca 2 (R/λ) 2 is derived for a film much thinner than that predicted by the Bretherton law. Moreover, both the 2/3 and the quadratic laws can be unified into the effective 2/3 law, with the viscosity µ replaced by an apparent viscosity µ app = µh ∞ /(λ + h ∞ ). A similar extension can also be made for coating over textured surfaces where apparent slip lengths are large. Further insights can be gained by making a connection with drop spreading. We find that the new quadratic law can lead to θ d ∝ Ca 1/2 for the apparent dynamic contact angle of a spreading droplet, subsequently making the spreading radius grow with time as r ∝ t 1/8 . In addition, the precursor film is found to possess f ∝ Ca −1/2 in length and therefore spreads as f ∝ t 1/3 in an anomalous diffusion manner. All these features are accompanied by no-slip-to-slip transitions sensitive to the amount of slip, markedly different from those on no-slip surfaces. Our findings not only provide plausible accounts for some apparent departures from no-slip predictions seen in experiments, but also offer feasible alternatives for assessing wall slip effects experimentally.