Spider-Inspired Knotted Geometries for Passive Water Harvesting

Overview

The purpose of this project was to investigate whether optimizing spider silk–inspired geometrical structures could improve fog-harvesting efficiency. Spider silk naturally captures water due to periodic spindle-knot geometries that promote droplet nucleation and directional transport. This project aimed to redesign and optimize these bioinspired geometries to maximize water collection while maintaining manufacturability using 3D printing. An initial bioinspired fiber geometry was designed based on published spider silk structures, incorporating periodic knots and grooves. The design was iteratively redesigned by modifying parameters such as knot spacing, knot curvature, groove depth, and surface tapering to improve droplet formation and transport. Each design iteration was fabricated using FDM 3D printing and tested in a controlled fog environment. Water collection efficiency was measured by mass of collected water over time and compared between designs. Time-lapse recordings were used to observe droplet behavior and inform each design change. The redesigned geometries showed measurable differences in fog collection performance. The single most impactful change was the addition of longitudinal grooves between knots in Iteration 3, which introduced capillary transport channels and produced a 49.5 percentage-point jump in efficiency. Iteration 6 deliberately reduced knot concavity to confirm it was the critical variable driving the Laplace pressure gradient — performance dropped 12.7%, confirming this hypothesis. The optimized design (Iteration 5) collected 104% more water than the smooth control fiber. Overall, optimized geometries significantly outperformed the baseline, confirming that geometry alone can more than double fog-harvesting efficiency. Future work could involve micro-scale fabrication and surface chemistry modifications to further enhance performance.

Competition history

• CSEF 2026 Environmental Engineering (Senior Division) · Entry S-11-35

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