Fig. 1
Schematic diagram of the ballistocardiogram (BCG) sensing system and sensor structure. (a) System setup. BCG and electrocardiogram (ECG) signals are recorded simultaneously using a sensing mattress with an embedded sensor. (b) Sensor flexibility. (i–iv) Demonstrations of the sensor’s flexibility and its integrated module. (c) Structural layers. The mattress consists of a sensitization layer (including two parts: the top is a specially hardened polyvinyl chloride material, and the second is a high-density sponge; both components are designed to enhance sensing sensitivity), a sensing layer, a support layer, and a buffer layer. (d) Working principle. The sensitized optical fiber deforms in response to cardiac-induced vibrations. (e) Signal transmission. Mechanical input modulates the optical signal, producing the processed BCG waveform.
