小氣泡很容易吸附在固體表面是由於一般基材都存在著接觸角遲滯 (Contact angle hysteresis, CAH) ，一旦浮力克服了毛細力，小氣泡就可以在極低接觸角遲滯的基材表面下緩緩移動，並且，氣泡在接觸角遲滯很小的超疏水表面下形狀相當平坦。本研究製備了兩種能在水中維持穩定的超疏水基材，觀察小氣泡於其下的運動行為。實驗結果顯示，體積為3~15 ul的小氣泡在超疏水表面下之垂直移動速率大於氣泡自由浮升速度 (此時雷諾數約為400~800)。隨著基材傾斜角度增加，氣泡滑移速度存在最大值，前方投影面積也呈現單調遞增，阻力係數與自由浮升氣泡相同。而氣泡滑移時的阻力較小則歸因於氣泡在超疏水基材上有較小的前方投影面積。;Tiny bubbles readily stick onto substrates due to contact angle hysteresis (CAH). A tiny bubble can slide slowly on a surface with ultralow CAH once buoyancy overcomes capillarity. The bubble shape is very flat on a superhydrophobic surface which possesses nearly vanishing CAH. A superhydrophobic surface with the stability in water is fabricated to observe the sliding motion of tiny bubbles. It is surprising to find that bubbles of 3~15 ul slide beneath the superhydrophobic surface at a vertical ascent rate faster than freely rising ones of Re~O(100). As the tilted angle increases, there exists a maximum velocity, the frontal area of the bubble rises monotonically, and the drag coefficient remains essentially the same as that of a freely rising bubble. Consequently, the small drag force associated with sliding bubbles is attributed to their substantially small frontal areas on superhydrophobic surfaces.
