Non-hygroscopic ionogel-based humidity-insensitive iontronic sensor arrays for intra-articular pressure sensing
Junli Shi, Sai Xie, Zhiguang Liu, Minkun Cai, Chuan Fei Guo
Abstract
ABSTRACT Implanted pressure sensors can provide pressure information to assess localized health conditions of specific tissues or organs, such as the intra-articular pressure within knee joints. However, the prerequisites for implanted sensors pose greater challenges than those for wearables or for robots: aside from biocompatibility and tissue-like softness, they must also exhibit humidity insensitivity and high-pressure resolution across a broad pressure spectrum. Iontronic sensors can provide superior sensing properties, but they undergo property degradation in wet environments due to the hygroscopic nature of their active component: ionogels. Herein, we introduce a humidity-insensitive iontronic sensor array based on a hydrophobic and tough ionogel polymerized in a hydrophobicity transition yielding two hydrophobic phases: a soft liquid-rich phase that enhances ionic conductivity and ductility, and a stiff polymer-rich phase that contributes to superior toughness. We demonstrate the in vivo implantation of these sensor arrays to monitor real-time intra-articular pressure distribution in a sheep model, while assessing knee flexion with an angular resolution of 0.1° and a pressure resolution of 0.1%. We anticipate that this sensor array will find applications in various orthopedic surgeries and implantable medical devices.