REDUCTION OF SKIN STRETCH INDUCED MOTION ARTIFACTS IN ELECTROCARDIOGRAM MONITORING USING ADAPTIVE FILTERING

Cardiovascular disease (CVD) is the leading cause of death in many regions worldwide, accounting for nearly one third of global deaths in 2001. Wearable electrocardiographic cardiovascular monitoring devices have contributed to reduce CVD mortality and cost by enabling the diagnosis of conditions with infrequent symptoms, the timely detection of critical signs that can be precursor to sudden cardiac death, and the long-term assessment/monitoring of symptoms, risk factors, and the effects of therapy. However, the effectiveness of ambulatory electrocardiography to improve the treatment of CVD can be significantly impaired by motion artifacts which can cause misdiagnoses, inappropriate treatment decisions, and trigger false alarms. Skin stretch associated with patient motion is a main source of motion artifact in current ECG monitors. A promising approach to reduce motion artifact is the use of adaptive filtering that utilizes a measured reference input correlated with the motion artifact to extract noise from the ECG signal. Previous attempts to apply adaptive filtering to electrocardiography have employed either electrode deformation or acceleration, body acceleration, or skin/electrode impedance as a reference input, and were not successful at reducing motion artifacts in a consistent and reproducible manner. This has been essentially attributed to the lack of correlation between the reference input selected and the induced noise. In this study, motion artifacts are adaptively filtered by using skin strain as the reference signal. Skin strain is measured non-invasively using a light emitting diode (LED) and an optical sensor incorporated in an ECG electrode. The optical strain sensor is calibrated on animal skin samples and finally in-vivo, in terms of sensitivity and measurement range. Skin stretch induced artifacts are extracted in-vivo using adaptive filters. The system and method are tested for different individuals and under various types of ambulatory conditions with the noise reduction performance quantified

Engineering Novel High-Resolution Bioelectronic Interfaces From Mxene Nanomaterials

At the interface between Man and Machine are electrode technologies. Using recording electrodes, it is possible to observe and monitor the activity of neurons or nervous tissue, affording us with an understanding of the basic dynamics underlying behavior and disease. By interacting with the nervous system through stimulating electrodes, it is possible to impact brain function, or evoke muscle activation and coordination, paving the way for treatments to severe neurological and neuromuscular disorders. However, despite the exciting promises of electrode technologies, current state-of-the-art platforms feature stiff and high-impedance materials, which are incompatible with soft biological tissue. Additionally, many current technologies suffer from shorter lifetimes than may be desirable for a truly chronic implant or wearable health monitoring device. Recently, there has been a shift in focus towards two-dimensional nanocarbons as alternative materials for superior electrode technologies. This comes as a result of the enhanced flexibility, biocompatibility, and electronic and electrochemical properties that most carbon-based nanomaterials exhibit. In particular, the 2D nanomaterial titanium carbide MXene (Ti3C2Tx) has very recently shown great promise for a variety of biomedical applications. However, the long-term stability of Ti3C2Tx has not been fully explored, and it is still unknown whether Ti3C2Tx can be used for chronic bioelectronic applications. Accordingly, in this thesis, I address and explore the key advantages of Ti3C2Tx for biopotential sensing, with a particular emphasis on validating this unique material for chronic recording studies. First, I demonstrate the superior advantages of Ti3C2Tx for direct recording of biopotential signals at the skin level in humans. Second, I define the long-term stability of Ti3C2Tx MXene in dried film form, and explore modifications in synthesis and film assembly to improve the material’s lifetime. Third, I fabricate and validate Ti3C2Tx-based epidermal sensors that exhibit comparable recording capabilities to state-of-the-art clinical electrodes, firmly establishing Ti3C2Tx electrode technologies for future, chronic experiments. The processing and fabrication methods developed herein translate into mature technologies with unique properties that are comparable to state-of-the-art designs, thereby offering a novel bioelectronic platform with the potential to benefit a variety of fields in both the research and clinical settings