From Functional Nanomaterials to Trustworthy Wearable Sensing Systems: A Cross-Layer Review of Bioelectronic Interfaces, Wireless and Power Integration, Artificial Intelligence Inference/Interpretation, and Human-Centred Validation

Material-level sensitivity or conductivity alone does not determine whether a wearable sensor produces trustworthy data. The signal must survive body coupling, packaging, wireless transfer, power constraints, and algorithmic interpretation. This cross-layer critical review examines six connected evidence streams: functional nanomaterial platforms, epidermal and implantable bioelectronic interfaces, wireless readout and power, integrated wearable platforms, artificial intelligence (AI)-based interpretation, and human-centred applications. Hysteresis and drift, interface instability, motion and environmental exposure, readout and power limits, placement and calibration dependence, and inter-user variability can degrade information across these layers. Robustness testing and claim-matched validation are needed to establish what the resulting outputs support. We therefore compare technologies through the failure modes and evidence requirements that persist after integration, rather than through isolated peak metrics. The synthesis offers conditional material-selection criteria for specific device roles, distinguishes demonstrated component functions from application-level claims, and identifies the reporting conditions and use-dependent validation priorities needed to interpret those claims.