Monolithic Integration of Closed-Loop Thermal Actuation and Temperature Sensing in a Thin-Film System-on-Glass Designed for Culture and Electroanalytical Detection of Living Bacteria

Point-of-care electroanalytical platforms for viable bacteria detection require local incubation and temperature control while maintaining compatibility with microfluidic handling and optical detection. This work presents a thin-film MEMS-based System-on-Glass (SoG) designed as a thermo-optical module for a four-site electrochemical bacterial-sensing platform. The SoG integrates a microfabricated double-spiral metal heater on one side of the glass substrate and six hydrogenated amorphous silicon (a-Si:H) temperature sensors along with eight complementary photosensors on the opposite side. The heater geometry was optimized through electrothermal simulations, which also established a linear relationship between the sensor and water temperature used to define the closed-loop setpoint. Infrared thermography on fabricated prototypes confirmed the simulated thermal distribution, yielding a mean temperature of 37.0 °C and a spatial variation from 36.4 to 37.7 °C across the active region. The temperature sensors showed a linear, reproducible response of approximately −4 mV/°C in two prototypes, while the photosensors exhibited dark currents in the 10−13 A range and a peak responsivity of 0.27–0.28 A/W at approximately 540–550 nm. Dedicated control software closed the loop between integrated sensing and actuation, regulating the temperature at 37 °C with an overshoot of 0.7 °C, a settling time of 140 s, and steady-state fluctuations confined within a single quantization step of the acquisition electronics. These results demonstrate the suitability of the SoG as a compact, controllable microscale thermo-optical platform for incubation, actuation, and complementary optical monitoring in point-of-care electroanalytical bacterial sensing.