Escobedo, PabloCarvajal, Miguel ACapitán-Vallvey, Luis FFernández-Salmerón, JoséMartínez-Olmos, AntonioPalma, Alberto J2025-01-072025-01-072016-07-14https://hdl.handle.net/10668/26352This work presents the design, fabrication, and characterization of a passive printed radiofrequency identification tag in the ultra-high-frequency band with multiple optical sensing capabilities. This tag includes five photodiodes to cover a wide spectral range from near-infrared to visible and ultraviolet spectral regions. The tag antenna and circuit connections have been screen-printed on a flexible polymeric substrate. An ultra-low-power microcontroller-based switch has been included to measure the five magnitudes issuing from the optical sensors, providing a spectral fingerprint of the incident electromagnetic radiation from ultraviolet to infrared, without requiring energy from a battery. The normalization procedure has been designed applying illuminants, and the entire system was tested by measuring cards from a colour chart and sensing fruit ripening.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/microcontrolleroptical sensorpassive RFID tagprinted electronicsscreen printingspectral fingerprintresearch article27428973open access10.3390/s160710851424-8220PMC4970131https://www.mdpi.com/1424-8220/16/7/1085/pdf?version=1468497737https://pmc.ncbi.nlm.nih.gov/articles/PMC4970131/pdf