Affective computing depends on biosensors capable of detecting physiological signals associated with human emotions. Chitosan, a naturally occurring cationic polysaccharide derived from chitin, has emerged as a promising platform for such devices due to its renewability, biodegradability, biocompatibility, and ease of chemical modification. Its abundant amino and hydroxyl groups provide versatile sites for derivatization, enabling tailored solubility, mechanical performance, and functional responsiveness. These attributes make chitosan well suited for wearable and implantable emotion-sensing systems; however, challenges remain, including environmental stability, signal drift under large deformation, and maintaining long-term skin comfort. This review provides an interdisciplinary overview of chitosan’s structural, solution, and interfacial properties, demonstrating how these characteristics can enhance biosensor performance in affective computing applications. Advances in chemical modification are evaluated for their roles in improving solubility, conductivity, selectivity, and mechanical robustness. Persistent challenges, including reproducibility, durability, and biocompatibility under real-world conditions, are discussed. Finally, future perspectives are outlined, focusing on greener production methods, multi-modal sensor integration, and the expansion of chitosan-based technologies into new emotion-aware application domains.

Semiconductor electrodes offer powerful routes to engineer electrochemical function, yet predicting surface confined charge transfer remains challenging because crystallography and doping reshape interfacial structure, band bending, and potential distribution. Here we map these coupled effects using ferrocene (Fc) monolayers grafted onto hydrogen-terminated p- and n-type Si(100), Si(110), and Si(111). Successful functionalization was confirmed by X-ray photoelectron spectroscopy and cyclic voltammetry. The Fc surface coverage (Γ) is strongly facet dependent and, in particular, doping reverses the facet selectivity: p-type follows (100) > (110) > (111), whereas n-type follows (111) > (110) > (100). In contrast, the Fc/Fc⁺ mid-point potential shows a consistent orientation hierarchy for both dopings ((100) > (110) > (111)) with an additional ~20–40 mV positive shift on n-type relative to p-type, indicating robust redox energetics with doping-controlled offsets. Peak widths exceed the ideal surface-confined limit and, together with impedance responses, point to non-ideal behavior dominated by interfacial electrostatics rather than ohmic artifacts. This facet-by-doping map clarifies how the silicon surface structure and electronic boundary conditions partition their influence across the monolayer formation and redox energetics, providing guidance for silicon-based molecular electrochemical interfaces in sensing and molecular electronics.