Machine learning-based optimal design of fibrillar adhesives.

Fibrillar adhesion, observed in animals like beetles, spiders and geckos, relies on nanoscopic or microscopic fibrils to enhance surface adhesion via 'contact splitting'. This concept has inspired engineering applications across robotics, transportation and medicine. Recent studies suggest that functional grading of fibril properties can improve adhesion, but this is a complex design challenge that has only been explored in simplified geometries. While machine learning (ML) has gained traction in adhesive design, no previous attempts have targeted fibril-array scale optimization. In this study, we propose an ML-based tool that optimizes the distribution of fibril compliance to maximize adhesive strength. Our tool, featuring two neural networks (NNs), recovers previous design results for simple geometries and introduces novel solutions for complex configurations. The predictor NN estimates adhesive strength based on random compliance distributions, while the designer NN optimizes compliance distribution to achieve maximum strength using gradient-based optimization. This method significantly reduces test error and accelerates the optimization process, offering a high-performance solution for designing fibrillar adhesives and micro-architected materials aimed at fracture resistance by achieving equal load sharing.