Martín Escudero, María Del PilarCabanas, Ana M.2026-02-242026-02-242025-12Martín-Escudero P, Cabanas AM. A multi-wavelength, rigid-flex wearable ring oximeter for mitigating motion and skin pigmentation challenges: Hardware development and preliminary characterization. Sensors and Actuators A: Physical 2025;396:117213. https://doi.org/10.1016/j.sna.2025.117213.0924-424710.1016/j.sna.2025.117213https://hdl.handle.net/20.500.14352/1329822025 Acuerdos transformativos CRUEPulse oximetry faces well-documented accuracy challenges related to skin pigmentation and motion artifacts, contributing to significant health disparities. In response, we present a wearable ring-type pulse oximeter designed to address these limitations through multi-wavelength sensing and stable anatomical coupling. The device features a rigid-flex printed circuit board integrating four LEDs (610–940 nm), dual photodetectors in transmission configuration, and a three-axis accelerometer. A Bluetooth-enabled microcontroller with adaptive acquisition firmware manages the system. The prototype was successfully fabricated and functionally validated. Optoelectronic characterization confirmed wavelength-dependent signal properties, with superior performance at longer wavelengths (740–940 nm). Preliminary testing on four healthy volunteers (Fitzpatrick skin types I–III) demonstrated reliable photoplethysmographic signal acquisition with improved signal-to-noise ratios at longer wavelengths, validating the hardware architecture’s capability to acquire high-quality multi-wavelength PPG signals. This platform establishes technical feasibility for future clinical validation. However, validation against arterial blood gas analysis across all Fitzpatrick types (I–VI), systematic motion artifact assessment, and melanin-compensated SpO2 algorithm development remain essential before clinical deployment.engAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/journal articlehttps://doi.org/10.1016/J.SNA.2025.117213https://www.sciencedirect.com/science/article/pii/S0924424725010192?via%3Dihubopen access796:61Pulse oximeterWearable sensorsPoint-of-care testing (POCT)PhotoplethysmographyMotion artifactsHealth equityMedicina del deporte32 Ciencias Médicas