Physicians’ understanding of bio-signals, measured using medical instruments, becomes the foundation of their decisions and diagnoses of patients, as they rely strongly on what the instruments show. Thus, it is critical and very important to ensure that the instruments’ readings exactly reflect what is happening in the patient’s body so that the detected signal is the real one or at least as close to the real in-body signal as possible and carries all of the appropriate information. This is such an important issue that sometimes physicians use invasive measurements in order to obtain the real bio-signal. Generating an in-body signal from what a measurement device shows is called “signal purification” or “reconstruction,” and can be done only when we have adequate information about the interface between the body and the monitoring device. In this research, first, we present a device that we developed for electrocardiogram (ECG) acquisition and transfer to PC. In order to evaluate the performance of the device, we use it to measure ECG and apply conductive textile as our ECG electrode. Then, we evaluate ECG signals captured by different electrodes, specifically traditional gel Ag/AgCl and dry golden plate electrodes, and compare the results. Next, we propose a method to reconstruct the ECG signal from the signal we detected with our device with respect to the interface characteristics and their relation to the detected ECG. The interface in this study is the skin-electrode interface for conductive textiles. In the last stage of this work, we explore the effects of pressure on skin-electrode interface impedance and its parametrical variation.

Physicians’ understanding of bio-signals, measured using medical instruments, becomes the foundation of their decisions and diagnoses of patients, as they rely strongly on what the instruments show. Thus, it is critical and very important to ensure that the instruments’ readings exactly reflect what is happening in the patient’s body so that the detected signal is the real one or at least as close to the real in-body signal as possible and carries all of the appropriate information. This is such an important issue that sometimes physicians use invasive measurements in order to obtain the real bio-signal. Generating an in-body signal from what a measurement device shows is called “signal purification” or “reconstruction,” and can be done only when we have adequate information about the interface between the body and the monitoring device. In this research, first, we present a device that we developed for electrocardiogram (ECG) acquisition and transfer to PC. In order to evaluate the performance of the device, we use it to measure ECG and apply conductive textile as our ECG electrode. Then, we evaluate ECG signals captured by different electrodes, specifically traditional gel Ag/AgCl and dry golden plate electrodes, and compare the results. Next, we propose a method to reconstruct the ECG signal from the signal we detected with our device with respect to the interface characteristics and their relation to the detected ECG. The interface in this study is the skin-electrode interface for conductive textiles. In the last stage of this work, we explore the effects of pressure on skin-electrode interface impedance and its parametrical variation.

X-ray detector windows must be thin enough to transmit sufficient low-energy x-rays, yet strong enough to withstand up to an atmosphere of differential pressure. Traditional low-energy x-ray windows consist of a support layer and pressure membrane spanning that support. Numerical modeling of several x-ray windows was used to show that both low- and high-energy x-ray transmission can be improved by adding a secondary support structure. Finite element analysis of the x-ray window models showed that the stress from a typical applied load does not exceed the ultimate strength or yield strength of the respective materials. The specific x-ray window models developed in this work may serve as a foundation for improving commercial windows, especially those geared toward low-energy transmission. For local mechanical film testing, microcantilevers were cut in suspended many-layer graphene using a focused ion beam. Multipoint force-deflection mapping with an atomic force microscope was used to record the compliance of the cantilevers. These data were used to estimate the elastic modulus of the film by fitting the compliance at multiple locations along the cantilever to a fixed-free Euler-Bernoulli beam model. This method resulted in a lower uncertainty than is possible from analyzing only a single force-deflection. The breaking strength of the film was also found by deflecting cantilevers until fracture. The average modulus and strength of the many-layer graphene films are 300 GPa and 12 GPa, respectively. The multipoint force-deflection method is well suited to analyze films that are heterogeneous in thickness or wrinkled. Bioimpedance can be measured by applying a known current to the tissue through two (current carrying) electrodes and recording the resulting voltage on two different (pickup) electrodes. Bioimpedance has been used to detect heart rate, respiration rate, blood pressure, and blood glucose. A wrist-based wearable bioimpedance device can measure heart rate by detecting the minute impedance changes caused by the modulation of blood volume in the radial artery. Using finite element analysis, I modeled how electrode position affects sensitivity to pulsatile changes. The highest sensitivity was found to occur when the pickup electrodes were centered over the artery. In this work, we used microfabricated carbon infiltrated-carbon nanotube electrodes to measure the change in contact bioimpedance for dry electrodes, and identical electrodes with a wet electrolyte, on five human subjects in the range of 1 kHz to 100 kHz. We found that the acclimated skin-electrode impedance of the dry electrodes approached that of the wet electrodes, especially for electrodes with larger areas. We also found that the acclimation time does not appear to depend on electrode area or frequency. The skin-electrode impedance after acclimation does depend on electrode area and frequency, decreasing with both. This work shows that if care is taken during the acclimation period, then dry carbon composite electrodes can be used in bioimpedance wearable applications.