Bio-inspired flexible optical microfiber sensor with nanohemisphere array microstructure for ultra-sensitive detection of skin signals

We propose the utilization of a bio-inspired nanohemispherical array of microstructure flexible optical micro/nanofibers sensor (NHSAMNFS) designed for highly sensitive detection of epidermal signals and cardiovascular health assessment. NHSAMNFS builds a flexible wearable self-mixing optical sensor by assembling MNF in a polydimethylsiloxane (PDMS) film with a surface modified nanohemispheres (400 nm diameter) array, where the micro/nanofiber (MNF) sensor is used to sense physiological signals. PDMS with a surface modified nano-hemispherical array is used to eliminate misalignment and increase the sensitivity of sensing pressure. Due to the high flexibility of PDMS and its surface modified nano-hemispherical array microstructure, the sensing element can reliably transmit pressure stimuli into interpretable optical signals with high fidelity, allowing instantaneous pressure perception. The sensor, measuring 20×20 mm in size, boasts a sensitivity of 0.102mV/kPa, with a rise time of 3.7 ms and a fall time of 6.26 ms. By tracking fluctuations in the reflected light power of MNF within PDMS, real-time monitoring of the fingertip pulse wave is achieved. Extracting cardiovascular vital signs from this pulse signal enables the evaluation of cardiovascular health status, yielding results consistent with human physiological characteristics. This non-invasive, continuous, and precise cardiovascular health monitoring, facilitated by wearable devices, holds significant promise for applications in human health monitoring, as well as in the prevention and diagnosis of cardiovascular diseases.