Humidity‐Resistant <scp>Def‐ZIF‐8/PPY/BC@PDMS</scp> Composite for Dual <scp> NO ₂ </scp> and Strain Detection

ABSTRACT The growing demand for multifunctional sensors in wearable systems has prompted the need for materials that simultaneously support gas sensing and mechanical strain detection. However, current flexible sensing materials still suffer from issues such as response hysteresis, poor humidity resistance, and lack of antibacterial properties. Herein, we developed a ternary flexible composite by integrating defect‐engineered ZIF‐8, conductive polypyrrole (PPY), and bacterial cellulose (BC), which was further encapsulated with polydimethylsiloxane (PDMS) to form the Def‐ZIF‐8/PPY/BC@PDMS composite. The results demonstrated that with 2–3 layers of PDMS, the sensor achieved a fast and stable NO 2 response (9.3% at 10 ppm), with reliable recovery. Under 80% relative humidity, PDMS reduced humidity‐induced signals from 34% to 10.3%, confirming markedly improved moisture resistance. The incorporation of a PDMS layer enabled enhanced stress sensing, reducing the response/recovery times to 0.4/0.3 s from 0.9/0.8 s in the uncoated structure. The sensor demonstrated high fidelity in recognizing complex biomechanical signals such as swallowing, walking, and finger articulation. Furthermore, antibacterial testing confirmed 42.18% and 64.69% inhibition against Escherichia coli and Staphylococcus aureus , respectively. This multifunctional composite simultaneously optimizes gas sensing, mechanical flexibility, humidity resistance, and antibacterial efficacy, paving the way for advanced materials in fully integrated wearable sensing technologies.