Bioinspired Elastic Liquid Transistor.

Directional liquid transport with controllable spreading speed remains challenging, as most existing systems focus on transport direction rather than speed regulation. Inspired by the regional spreading-speed differences governed by parametrically distinct trichomes on the inner pitcher wall of Heliamphora nutans, we fabricated a series of artificial ciliated surfaces with independently controlled height and observed distinct water spreading speeds across these surfaces. To understand the mechanism, we captured side-view micrographs of the advancing liquid front, which revealed that spreading is primarily driven by capillary wicking along the sidewalls of neighboring cilia. Based on this mechanistic insight, we developed a normalized predictive model, which was subsequently validated against a broader set of height-spacing combinations, confirming its generality. Guided by this understanding, we report a bioinspired elastic liquid transistor (BELT) that achieves real-time, stepless regulation of liquid transport speed on an open surface. Beyond unidirectional gating, the BELT enables coordinated control of spreading direction and speed in orthogonal directions. Owing to its elasticity, the BELT retains its gating function under twisting deformation, demonstrating its compatibility with nonplanar and soft surfaces.