  A body area network (BAN) involving wearable sensors populated around the
human body can continuously monitor physiological signals, finding applications
in personal healthcare and athletic evaluation. Existing near-field
communication (NFC)-enabled BAN solutions, while facilitating reliable and
secure interconnection among battery-free sensors, face challenges such as
limited spectral stability against external interference. Here we demonstrate a
textile metamaterial featuring a coaxially-shielded internal structure designed
to mitigate interference from extraneous loadings. The metamaterial can be
patterned onto clothing to form a scalable, customizable network, enabling
communication between NFC-enabled devices and developed battery-free textile
NFC sensing nodes placed within the network. Proof of concept demonstration
shows the metamaterial's robustness against mechanical deformation and exposure
to lossy, conductive saline solutions, underscoring its potential applications
in wet environments, particularly in athletic activities involving water or
significant perspiration, offering insights for the future development of radio
frequency components for a robust BAN at the system level.
