Three-core fiber sensor based on antibody-functionalized asymmetric C-shaped microcavities for BSA and temperature sensing

An asymmetric dual C‑shaped microcavity sensor based on three‑core fiber (TCF) is proposed and fabricated for label‑free bovine serum albumin (BSA) detection and temperature sensing. Two spatially isolated microchannels of different lengths are directly constructed in the side cores of TCF. One microchannel is modified with BSA‑specific antibodies for specific biomolecular recognition, and the other is filled with thermo‑responsive material to realize temperature sensing. Benefiting from this structural design, high‑sensitivity specific BSA detection and real‑time temperature monitoring are successfully integrated into a single optical fiber. Experimental results verify prominent BSA sensing performance and reliable temperature response of the proposed sensor. After antibody functionalization, the sensor delivers 4.3‑fold higher BSA detection sensitivity than the sensor without antibody treatment, and accurate local temperature measurement is realized in the low‑temperature region. With merits of high integration, good mechanical stability, and low fabrication cost, the presented sensor shows application potential in biological protein analysis, precision medical diagnosis, and low‑temperature reagent preservation.