Multiphysics FDTD study of a silver–gold complementary layer D-shaped optical fiber sensor for biomechanical characterization of living materials

Living materials integrated into biosensing platforms encompassing cellular assemblies, tissue constructs, enzymatic complexes, and antibody-based recognition elements confer unparalleled specificity and sensitivity toward target analyte detection within complex environmental matrices. Recent decades have witnessed a substantial surge in research endeavors dedicated to the rational engineering and optimization of such living-material-based biosensing architectures, driven by their compelling advantages across diverse fields. In this study, we present the design and numerical characterization of a fiber optic-based chemical sensor incorporating a silver–gold bimetallic nanocomplementary layer. Systematic investigation of the influence of geometric parameters specifically, the thickness of the complementary layer and the fiber core depth on propagation losses was performed. At an optimal complementary layer thickness of 0.5 μm and a fiber depth of 0.1 μm, a maximal confined loss of 1.4 dB/cm was achieved in response to an analyte refractive index alteration of 1.34. Furthermore, our findings demonstrate that an increased fiber core-to-cladding distance (quantified by fiber depth) leads to a pronounced reduction in confinement losses, accompanied by a narrowing of interpeak wavelength separation down to 0.8 μm. Collectively, these results underscore the profound potential of living-material-based platforms as a transformative paradigm in biomechanical and biophotonic signal transduction, with far-reaching implications for next-generation biosensing technologies.