Flexible electronics based efficient front-end circuits for noninvasive continuous health monitoring in biomedical wearable devices

Abstract

With the new habits of lifestyle, new health problems are arising and demands continuous health monitoring. Wearable technology will revolutionize our lives in the upcoming years. To enable widespread usage of such devices, it is important to maximize their functionality while minimizing manual intervention, with extended life time, flexibility and at low-cost. The advancement of miniature and flexible devices has fostered a dramatic growth of interest in this technology. Currently, most of the wearable biomedical systems are c-Si based, which are typically rigid, bulky (due to battery size), expensive in terms of fabrication cost and requires some external interface. They limit mobility and comfort of the wearer. Typically in hospitals, in order to monitor ECG signals, which is a part of routine for the cardiovascular patients, is done through ECG measurement equipment with many electrodes and long wires, which limits the patient’s mobility. In the same way, BP measurement using cuffs is very inconvenient when frequent measurements need to be recorded. Both these approaches need human interaction. Though some commercial wearable devices are available for biomedical monitoring, which are confined to few biological signal monitoring that includes ECG, EEG, temperature sensor or for the measurement of pulse rate. Compact, reliable and light weight systems, that can monitor the variety of biological signals is still an open challenge. Researchers have been actively seeking for innovative solutions and new technologies that could improve the quality of patient care meanwhile reduce the cost through early detection of serious health problems. In order to address these issues, this work targets to build a self-contained noninvasive flexible real-time health monitoring front-end, which is compact and do not limit the wearer’s mobility. The proposed system can be successfully used by many people ranging from infants, sportsman, elderly people and post-hospitalized patients, where, continuous health monitoring is vital. Further the idea can be extended to store the biological signals over a time period so that doctor can have complete record of the patient’s health condition. In order to bring the proposed biomedical wearable front-end into a reality, many signal conditioning and processing circuits need to be developed with oxide TFT technology (a-IGZO), as it can facilitate fabrication of circuits on flexible substrates. The circuits that are included are on-chip power supply (bootstrapping circuit), clock generators (ring oscillators), pre-amplifier to amplify biomedical signals for pre-processing, low-pass filters (anti-aliasing filter) and ADC (Analog-to-Digital Converter). The biological signals (output of the bio-sensors) need to be processed through these analog and mixed signal blocks in order to transmit the data to the server/smart phone so that in case of an emergency, an alert can be sent to the doctor/wearer in order to provide immediate medical assistance. This type of remote monitoring of the important biological signals in real-time data can significantly minimize health risks