Autonomous Motility of Polymer Films

Abstract

Adaptive soft materials exhibit a diverse set of behaviors including reconfiguration, actuation, and locomotion. These responses however, are typically optimized in isolation. Here, the interrelation between these behaviors is established through a state space framework, using Nylon 6 thin films in a humidity gradient as an experimental testbed. It is determined that the dynamic behaviors are a result of not only a response to but also an interaction with the applied stimulus, which can be tuned via control of the environment and film characteristics, including size, permeability, and coefficient of hygroscopic expansion to target a desired behavior such as multimodal locomotion. Using these insights, it is demonstrated that films simultaneously harvest energy and information from the environment to autonomously move down a stimulus gradient. Improved understanding of the coupling between an adaptive material and its environment aids the development of materials that integrate closed loop autonomous sensing, actuation, and locomotion.

Autonomous multimodal locomotion, oscillation, and reconfiguration are demonstrated in commodity polymer films. A behavioral state space is developed that connects these behaviors to the common underlying mechanism. Films are shown to harvest not only energy but also information from their environment, resulting in directed locomotion down a humidity gradient.

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