Structural Capillarity: Programming Liquid Behavior in Open Microfluidic Platforms

Capillary-driven manipulation, governed by structural design and surface energy regulation, offers a powerful approach to passive fluid control. Open microfluidic platforms transcend the limitations of enclosed channels by leveraging sophisticated 3D architectures, which grant exceptional geometric freedom and enable precise spatiotemporal liquid handling. These systems exhibit unparalleled versatility, intervenability, and expandability, supporting operations ranging from droplet transport to continuous flow regulation. This review examines the underlying capillary mechanisms, advanced fabrication methods, and functional capabilities of open microfluidic platforms. We highlight their potential to overcome longstanding challenges in conventional microfluidics and explore their growing applications in fields such as biomedicine, energy, and soft robotics. As an emerging paradigm, open capillary microfluidics is establishing a distinct and transformative role in the development of next-generation autonomous fluidic systems.