Enhanced Interface between Conductive Fillers and Elastomeric Ionomers for Highly Sensitive and Stretchable Strain Sensors toward Human Motion Detection

Abstract

Flexible elastomer-based wearable sensors have gained tremendous attention due to their potential application in personal health diagnosis and human motion detection. However, challenges persist in achieving high sensitivity, stretchability, and antibacterial properties simultaneously. Herein, ionic cross-linked bromide butyl rubber (BIIR) filled with ionic liquid butylimidazole (BI)-modified conductive carbon black (BCCB) is rationally designed and then fabricated into high-performance strain sensors by a facile solution mixing method. The BI not only ion-cross-linked the BIIR but also formed a strong interface between BIIR and conductive carbon black (CCB) through π–cation interactions, which facilitated the uniform dispersion of CCB throughout the BIIR matrix, leading to the formation of a conductive filler network. Based on the synergistic effect of the ionic cross-linking network and conductive filler network, the prepared BCCB/BIIR exhibited a low percolation threshold (1.75 wt %), high electrical conductivity (21.3 S/m), high tensile strength (4.9 MPa) and elongation at break >1200%, high sensitivity with gauge factor values of 9.41 at strains levels within 5% and 2048.89 at high strain levels, and excellent durability under cyclic working conditions. As a result, the BCCB/BIIR can be used as sensors for detecting both weak and large deformations induced by human activities, such as pulse, swallowing, and muscle and joint movements. Additionally, the sensor demonstrated over 99% antibacterial efficacy against Escherichia coli and Staphylococcus aureus, which can improve wearable comfort. The results suggest that the developed method provides a practical and large-scale production approach for fabricating high-performance sensors.