Biodegradable Smart Face Mask for Cough Acoustic Sensing.

We introduce Green Cough Sense, a biodegradable, battery-free smart face mask that incorporates a flexible, passive microphone for sensing cough acoustics in pulmonology. The device integrates a mesoscale-patterned 3 by 3 array of 1 cm2 circular drum-like membranes with a patch antenna, a planar resonator comprising a metallic radiating patch over a grounded dielectric substrate. Cough-induced acoustic vibrations are transduced into measurable shifts in the electromagnetic reflection coefficient (|S11|), which are measured by a vector network analyzer operating in zero-span mode for high-fidelity characterization. The system is fabricated entirely from sustainably sourced, biodegradable materials, including cellulose acetate, poly(lactic acid), and zinc, via a new green manufacturing process that combines laser machining with solvent- and adhesive-free low-temperature lamination technique with maximum bonding strength reaching 5.8 N/mm. Experimental validation of the mechanoacoustic response demonstrates absolute sensitivity of 0.045 μm/Hz; in vitro characterizations under monotone excitation show sensitivity of 0.13%/Pa; in situ validation with human participants confirms detection of mild, moderate, and severe cough events. Biodegradation under industrial composting confirms material breakdown with over 90% weight loss after 100 days, supporting a zero-waste end-of-life strategy.