Flexible wearable sweat sensors can monitor sweat continuously and non-invasively in real time. They give useful information about the human body at the molecular level. Because of their high performance, low cost, and small size, electrochemical sensors have received much attention for use in personal health monitoring.

In this thesis, a back-end electronic system for a flexible electrochemical sweat sensor is developed with several key modules for stable and accurate monitoring. The work begins with a review of recent studies on wearable sweat sensing, focusing on ion-selective electrodes, iontophoresis, impedance measurement, and system integration methods.
Then, the overall system design is introduced, including schematic and layout planning, and main circuit blocks such as power management, iontophoresis for sweat induction, and impedance measurement using the AD5933 chip. Firmware and data collection with an STM32 microcontroller are also described, covering signal sampling, impedance readout, and Bluetooth communication.

The experimental part presents the validation of the first prototype, showing the main functional tests, the problems found, and their solutions in the second-version PCB. The MCU, power management, Bluetooth communication, and iontophoresis modules operated reliably, while the ISE readout and impedance measurement using the AD5933 were only partially successful. The second-version PCB is built on a flexible polyimide substrate with local stiffeners, forming a ridge-flex bridge structure. This design improves both mechanical strength and flexibility for wearable use.