During this period, researchers pursued a convergence of optical and electrochemical transduction for biomedical sensors, emphasizing robust transducers and mediator-free architectures. Polymer-based immobilization of enzymes and direct electron transfer became central, enabling simpler, more stable amperometric sensors and paving the way for wearable, noninvasive devices. The field also saw rapid development of optical approaches, including fiber-optic oximetry and photoplethysmography, linking physiological signals to practical biomedical readouts.