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Multifunctional fibers are developed worldwide for enabling many new advanced applications. Among the multiple new functionalities that such fibers can offer according to their design, chemical composition and materials combination, the co-transmission of light and electrical signals is of first interest for sensing applications, in particular for optogenetics and electrophysiology. Multifunctional fibers offer an all-solid approach relying on new ionic conducting glasses for the design and manufacturing of next generation optrodes, which represents a tremendous upgrade compared to conventional techniques that requires the utilization of liquid electrolytes to carry the electrical signal generated by genetically encoded neuronal gated ion channels after optical excitation. After a systematic study conducted on different ion-conductive glass systems, silver phosphate-based glasses belonging to the AgI-AgPO3-WO3 and AgI−AgPO3−Ag2WO4 systems were found to be very promising materials for the target application. Several types of fibers, including single-core step-index fibers, multimaterial fibers made of inorganic and optical polymeric glasses have been then fabricated and characterized. Light transmission ranging from 400 to 1000 nm and electrical conductivity ranging from 10−3 and 10−1 S·cm−1 at room temperature (AC frequencies from 1 Hz to 1 MHz) were demonstrated with these fibers. Very sharp fiber tapers were then produced with high repeatability by using a CO2 laser optical setup, allowing a significant shrinking from the fiber (300 μm diameter) to the taper tip (25-30 μm diameter).
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