Cracking-Directed Dynamic Liquid Bridging for Autonomous Microdroplet Recession and Enrichment
The precise manipulation of microdroplets (diameter < 20 μm) on solid substrates is critical for applications in environmental monitoring, targeted drug delivery, clinical diagnostics, and public health. A major challenge is contact angle hysteresis (CAH), which pins droplets and impedes mobility. Here, we introduce a crack-mediated capillary bridging strategy for efficient capture and directional transport of microdroplets. The approach employs a stretchable elastomeric substrate with island-like microstructures. Under longitudinal tensile stress, controlled fracture generates densely packed, directionally oriented surface cracks. These fissures induce localized capillary forces that counteract adhesion-induced resistance, enabling programmable droplet motion. Experiments capturing airborne pathogenic agents demonstrated a 14.2-fold enhancement in enrichment efficiency compared to flat surfaces. This work integrates fracture mechanics with capillary-driven fluid dynamics, establishing a framework for next-generation microfluidic systems. The findings offer promising avenues for biosensing, pollutant analysis, and interdisciplinary applications.