Low Power Analog Techniques for Wearable Biosensors

Wearable biosensors show considerable promise in monitoring and assessing the real-time performance of athletes, the health status of patients, or the general well-being of interested users. Despite this promising status, wearables still face many challenges related to power consumption, device flexibilities, and sensor-circuit interface. For instance, in many current wearable devices, the user needs to replace/recharge the battery every day, which is inconvenient and ultimately limits the adoption of this technology. On the other hand, most wearables today focus on monitoring physical parameters (e.g., activity, respiration rate, etc.), or electrophysiology (e.g., ECG, EEG, etc.). In order to augment the richness of collected data, the next-generation of wearables will also be capable of monitoring underlying chemical homeostatis of the user, for example through measurement of glucose in interstitial fluid, lactate in saliva, or electrolytes in sweat. \\This thesis discusses the challenges of the next generation of wearable biosensors, and introduces some new biosensing systems and low-power instrumentation circuits for their implementation. These wearable systems have been implemented in different novel platforms including mouthguard, cell phone, and variable types of flexible temporary tattoos.The energy harvesting from other energy sources, such as sweat from the body, has been also considered as a viable means of powering the next generation of wearable devices. In this thesis, we investigated a few examples of this approach including an implementation of a fully self-powered biosensor system