Continuous vital monitoring during sleep and light activity using carbon-black elastomer sensors

The comfortable, continuous monitoring of vital parameters is still a challenge. The long-term measurement of respiration and cardiovascular signals is required to diagnose cardiovascular and respiratory diseases. Similarly, sleep quality assessment and the recovery period following acute treatments require long-term vital parameter datalogging. To address these requirements, we have developed “VitalCore”, a wearable continuous vital parameter monitoring device in the form of a T-shirt targeting the uninterrupted monitoring of respiration, pulse, and actigraphy. VitalCore uses polymer-based stretchable resistive bands as the primary sensor to capture breathing and pulse patterns from chest expansion. The carbon black-impregnated polymer is implemented in a U-shaped configuration and attached to the T-shirt with “interfacing” material along with the accompanying electronics. In this paper, VitalCore is bench tested and compared to gold standard respiration and pulse measurements to verify its functionality and further to assess the quality of data captured during sleep and during light exercise (walking). We show that these polymer-based sensors could identify respiratory peaks with a sensitivity of 99.44%, precision of 96.23%, and false-negative rate of 0.557% during sleep. We also show that this T-shirt configuration allows the wearer to sleep in all sleeping positions with a negligible difference of data quality. The device was also able to capture breathing during gait with 88.9%–100% accuracy in respiratory peak detection

Polymer sensor embedded, IOT enabled t-shirt for long-term monitoring of sleep disordered breathing

Sleep Disordered breathing is an increasingly common condition among the general population. Conventional sleep disordered breathing diagnosis depends on in-lab polysomnography, while at-home sleep test devices are becoming a more widespread. Both systems are cumbersome and typically data is collected offline, typically limiting use to only a few nights recording. We present the design, implementation and preliminary results from a novel IOT ready sleep test device named VitalCore The device utilizes electroresistive polymer sensors and accelerometer to measure respiratory, cardiac and actigraphy information. The device uses Bluetooth 5 to stream and transfer data and is capable of reliably acquiring high quality sleep data. The device significantly improves the user experience by completely concealing the hardware into a t-shirt while providing five days of battery life, full speed Bluetooth 5 live data streaming/ downloading with local storage capable of more than a year worth of sleep data

Live demonstration : morphic sensor for diagnosis of peripheral vascular disease

Peripheral vascular diseases, in particular including peripheral arterial disease and chronic venous insufficiency, affect hundreds of millions of people worldwide. These conditions are often symptomless and go undiagnosed. Early diagnosis is crucial for effective treatment and reducing personal and economic costs, particularly where early treatment is geared towards preventing lower extremity amputation. New diagnostic tools are needed to enable this earlier intervention [1]. We have developed a new low-cost, easy to use, non-invasive hemodynamic monitor, HeMo, to address this large and growing problem [2], [3]. This novel device can measure arterial blood flow from the entire limb and venous refilling in real-Time. In this manner, both peripheral arterial disease and chronic venous insufficiency may be diagnosed. Indeed, it is now in its first clinical trial in patients with peripheral vascular disease. We believe that this work will lead to the availability of a fast, easy to use and cost-effective vascular assessment tool, dramatically shortening the time to diagnosis and subsequently intervention, dramatically improving the prognosis of affected patients

Live demonstration : invisible vital monitoring

Continuous monitoring of vital functions such as reparation, pulse and body movement are important in sleep monitoring. The polysomnogram is considered the medical gold-standard means of assessing quality of sleep [1]. Polysomnography is expensive, has limited access, is uncomfortable and unsuitable as a continuous sleep quality assessment method. An alternative diagnostic device is required to improve treatment of sleep disordered breathing. In an attempt to address these issues, we present “VitalCore”, an “invisible” wireless sleep monitoring device integrated into the sleeping garment providing high quality vital sign information

Characterisation of morphic sensors for body volume and shape applications

Stretchable conductive materials are originally conceived as radio frequency (RF) and electromagnetic interference (EMI) shielding materials, and, under stretch, they generally function as distributed strain-gauges. These commercially available conductive elastomers have found their space in low power health monitoring systems, for example, to monitor respiratory and cardiac functions. Conductive elastomers do not behave linearly due to material constraints; hence, when used as a sensor, a full characterisation to identify ideal operating ranges are required. In this paper, we studied how the continuous stretch cycles affected the material electrical and physical properties in different embodiment impressed by bodily volume change. We simulated the stretch associated with breathing using a bespoke stress rig to ensure reproducibility of results. The stretch rig is capable of providing constant sinusoidal waves in the physiological ranges of extension and frequency. The material performances is evaluated assessing the total harmonic distortion (THD), signal-to-noise ratio (SNR), correlation coefficient, peak to peak (P-P) amplitude, accuracy, repeatability, hysteresis, delay, and washability. The results showed that, among the three controlled variables, stretch length, stretch frequency and fabric width, the most significant factor to the signal quality is the stretch length. The ideal working region is within 2% of the original length. The material cut in strips of >3 mm show more reliable to handle a variety of stretch parameter without losing its internal characteristics and electrical properties

Characterization of coated piezo-resistive fabric for respiration sensing

Electro-resistive band (ERB) or conductive elastomer can be also used as non-invasive bio-potential sensors. This stretchable conductive material gained acceptance in health monitoring systems due to their low cost, low power consumption and high flexibility. ERBs can be polarized with a current source to generate a voltage signal directly proportional to the change of length. However, the sensors require close contact with the patient’s skin to monitor bio-mechanical movements adequately. Direct contact with human skin causes inconsistent current leakage and result in low SNR. Isolating the ERB is important to avoid current leakage, provide protection by overstretching and easiness of wearing. However, not all stretchable material suitable to use as ERB substrate. In this work, we have compared two different conductive elastomers (rubber and fabric) stretched using a breathing simulator machine to compare the material performance. We have coated the ERBs with 3 different coating materials: Pinkysil, Transil and silicone tape, as well as raw bands. We have processed and analyzed all the collected signals using a wide range of measurements and calculations such as linearity, baseline change, Total Harmonic Distortion (THD), Signal to Noise Ratio (SNR), correlation coefficient and phase difference. We have discovered from the final results that the silicone tape serves as a good isolator material and shows reliable and consistent results. The conductive rubber also shows less noise and distortion across stretching in shorter stretch applications compared to the conductive fabric