The emergence of flexible wearable devices represents a significant leap forward in human-robot interaction (HRI), meeting the growing demand for both comfortable and versatile interfaces. Finger joint movements, the most intricate among human joint motions, require precise detection while comfortable deployment for seamless collaboration with robotic hands, which is hard for traditional rigid sensors. This study presents electronic slime crafted from a biocompatible polyvinyl alcohol (PVA) matrix combined with cost-efficient and highly effective carbon-based nanoparticles (graphite and carbon black) using a simple fabrication process. The electronic slime benefits from a unique island-bridge structure and tunneling effect between graphite flakes and carbon black granules, resulting in a high gauge factor of 2.95, a broad sensing range of up to 400%, and a low detection threshold of 1% strain. Easily applicable to fingers, this electronic slime is capable of detecting minute motion signals, such as subtle joint extensions and flexions. Additionally, it accurately captures finger motion signals to facilitate interaction with robotic fingers, underscoring its potential as a human-machine interface. This research paves the way for the development of ultra-flexible, readily deployable electronic skin suitable for wearable HRI applications.