Wireless E-Tattoos for Multimodal Biometric Sensing under Exercise and Extreme Temperatures
Abstract
The objective of this proposed research is to develop ultra-thin and ultra-soft noninvasive e-tattoo stickers that can wirelessly and reliably monitor human biometrics under exercise and extreme temperatures and are also chargeable on-the-go. Environmental stressors such as extreme temperature, extreme pressure, air quality etc. can cause irritation or even health problems. Soldiers subjected to such environmental stressors should be continuously monitored and evaluated for their health as well as the mission outcome. State-ofthe- art wearable sensors are limited in functionalities, accuracy, and battery life, cumbersome to wear, and susceptible to motion artifacts. Hence they are considered more as toys rather than medical devices. Unlike conventional machinery, the soft and deformable human body demands ultra-thin and ultra-soft sensors to form intimate contact with human skin for high-fidelity measurement especially under motion. Compared with conventional wearables, rugged and lightweight sensors also offer much better wearability, which is critical for long-term ambulatory monitoring of high-mobility subjects such as soldiers. Emerging hair-thin, skin-soft wearable electronics, the epidermal electronics, a.k.a electronic tattoos (e-tattoos), have been proven to afford intimate but non-irritating contact with human skin. As a result, e-tattoos have demonstrated superior signal-to-noise ratio (SNR) especially after extended periods of time and under various types of motion compared with conventional dry electrodes for electrophysiological sensing. More sensing modalities are desirable for comprehensive understanding of human physiology and evaluation of human performance. In addition to heart rate, other important biometrics include respiratory rate, core temperature, and whole body hydration. Moreover, such e-tattoos need to be wireless for mobile sensing and also need to be validated under exercise under extreme temperatures. On one chest-laminated wireless e-tattoo, we propose to synchronously and directly measure electrocardiography (ECG), respiratory rate (RR), skin temperature (ST), skin hydration (SH), and muscle hemoglobin concentration ([Hb]). ECG and SH will be measured through ultrathin dry electrodes made out of gold nanomembrane patterned into a filamentary serpentine network. RR will be measured through soft piezoresistive strain gauges made out of electrically conductive rubber (ECR). ST will be measured through off-the-shelf micro-thermistors integrated on the etattoo. Muscle [Hb] will be measured through near-infrared spectroscopy (NIRS) integrated on the e-tattoo, which has never been achieved before. We will be able to extract heart rate (HR) out of ECG and estimate core temperature (CT) out of existing algorithms of HR, RR, and ST. We hypothesize that we will be able to report whole body hydration (WBH) out of SH and muscle [Hb] measurements as when the body dehydrates, there are proportional increases in blood and muscle [Hb] as well as serum osmolality. The vital signs measured by the e-tattoos will be validated by gold standards. Specifically, the WBH estimated based on skin hydration (SH) and muscle [Hb] will be calibrated and validated through the gold standard of determining the WBH, the plasma osmolality and the reductions in body weight. Wireless data transmission will be mainly through Bluetooth Low Energy (BLE) although Long Term Evolution (LTE) will also be attempted. Wireless and even mobile charging will be through near field communication (NFC). The wireless e-tattoos will be tested in ambient condition, under exercise, and also under heat and cold stressors induced by a water perfused suit and exercise. The sensors will finally be evaluated under simulated field conditions while wearing combat clothing and a pack during prolonged maneuvers in a hot environment (e.g.; 33-35°C).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012112
Entities
People
- Nanshu Lu
Organizations
- Office of Naval Research
- United States Navy
- University of Texas at Austin