Spontaneous formation of picoliter water bridges

Picoliter water, ubiquitous at the microscale and predominantly confined between solids, underpins critical physical, chemical, and biological processes. Although vapor diffusion governs water evaporation in air, and capillarity inhibits evaporation at the nanoscale, neither mechanism fully accounts for the stability of picoliter water at the microscale. Here, we demonstrate that adsorption at solid interfaces can substantially inhibit evaporation, stabilizing picoliter water bridges beyond predictions from capillarity alone. Employing high-resolution X-ray imaging, we directly visualize the evolving geometry of picoliter water during evaporation and develop a physical model that disentangles the roles of capillarity and adsorption. Our results reveal that adsorption-driven inhibition is essential for maintaining water at the microscale, establishing a new framework for understanding and controlling water retention in natural and engineered systems. Water evaporation at the microscale is primarily governed by vapor diffusion and capillarity, but the stability of picoliter water bridges remained poorly explained. Here, the authors demonstrate that adsorption at solid interfaces can significantly inhibit evaporation, thereby enabling the spontaneous formation and long-term stability of picoliter water bridges through an energy-minimization mechanism, as visualized by X-ray imaging.