Sticky Yet Slippery: Molecular Ordering Reconciles Bubble-Surface Affinity With Ultralow Friction at the Nanoscale

A general understanding in wetting is that droplet stickiness and slipperiness are independent and do not necessarily change synchronously. However, it remains unclear whether bubbles behave similarly, making it challenging to achieve both strong interfacial affinity and low-friction mobility, crucial for controlling bubble dynamics in microfluidics, catalysis, and gas-liquid separation. Here, we show that molecular ordering within surface-tethered polydimethylsiloxane (PDMS) layers reconciles bubble stickiness and slipperiness, enabling bubbles to maintain robust attachment and ultralow friction. Remarkably, tuning PDMS from disordered networks to ordered brushes nearly doubles hydrophobic decay length (D₀, ∼0.8 to ∼1.4 nm) while significantly reducing friction, as quantified by bubble probe atomic force microscopy. Increasing brush thickness further extends D₀ to ∼1.9 nm and reduces friction by additional 60%. Molecular dynamics simulations attribute this "sticky-slippery" synergy to molecular ordering and homogenization, which reorganize interfacial water molecules into a well-defined depletion layer that strengthens hydrophobic interaction; simultaneously, coherent chain tilting and reorientation during bubble sliding preserve chain order and packing density, minimizing contact line pinning and energy dissipation. These findings unveil a universal molecular mechanism that reconciles bubble affinity with ultralow friction, establishing a general framework for engineering adaptive soft interfaces with programmable wetting, adhesion, and interfacial transport properties.