A Wireless, Passive Multimodal Wearable Sensor With Decoupled Sensing Capabilities.

Developing electronic skin (e-skin) that perceives multi-stimuli and even exceeds human skin sensing capacity remains a major challenge. Yet existing technologies focused mainly on tactile sensing suffer from poor superimposed multi-stimuli discrimination, external power dependence, and wired transmission modes. Here, we report an integrated wireless passive wearable sensor based on frequency-division inductance-capacitance (LC) resonator array, capable of simultaneously detecting superimposed multi-stimuli including pressure, odor and humidity, along with decoupling. The system's performance is designed and validated using three-dimensional full-wave electromagnetic simulations. Notably, pressure-sensing with an ultrafast response/recovery (∼5/6 ms) and high sensitivity (6.15 MHz·kPa-1) is enabled by a gradient-modulus trilayer hydrogel incorporating a micro-pyramidal patterned top-layer. Furthermore, the sensor demonstrates trace-level (200 ppb) NO2 detection without interference from humidity or pressure and exhibits high humidity sensitivity across a wide humidity range (2%-98% RH). Demonstration of this sensor as e-skin reveals capabilities surpassing previous devices, enabling wireless passive and decoupled detection of small applied mechanical pressure, trace-level NO2, and ambient humidity under complex stimuli conditions, showing high selectivity and minimal cross-sensitivity. The proposed system introduces a transformative approach, unlocking substantial benefits for a variety of wearable applications.