The field of wearable and smart textiles has seen rapid advancements due to progress in electronic devices and fabrication technologies. However, most existing textile electronics focus on single-modality sensing and cover small areas. This research addresses the need for a large-scale, multimodal physiological sensing platform that is comfortable, durable, and easily customizable. Two major classes of wearable electronics for healthcare are on-skin electronics and textile electronics. On-skin electronics, often in the form of patches, can precisely detect various physiological signals but are limited in area coverage and may be uncomfortable or impractical for long-term use or during dynamic activities. Textile electronics, integrated into clothing, offer advantages such as enhanced user mobility and comfort, but many lack scalability and stretchability needed for intimate skin contact sensing. This research aims to bridge these gaps by creating a tailored, electronic textile conformable suit (E-TeCS) capable of large-scale, spatiotemporal mapping of multiple physiological processes and physical movements. This is a valuable tool for clinicians, sports science, and other applications that require comprehensive physiological data. While distributed sensor networks exist, many require external readers for powering and data collection or rely on numerous individual devices, increasing complexity and bulk. The E-TeCS aims to create a centralized, system-on-textile garment with multiple functionalities and high manufacturability through utilizing high-throughput methods such as digital knitting. This method enables customization based on the user's requirements.

The authors review existing literature on flexible and stretchable electronic devices, wearable electronics for healthcare, and the integration of electronics into textiles. They highlight the limitations of existing on-skin and textile-based devices, emphasizing the lack of scalability for large-area sensing and the challenges associated with stretchability, washability, and cost-effective mass manufacturing. The existing wearable devices often focus on single-parameter measurement at specific body locations. The authors emphasize the need for distributed sensor networks capable of spatiotemporal mapping of multiple physiological processes across different body regions, citing examples in sleep studies, athletic performance analysis, and the detection of dermatome abnormalities. These existing solutions, although wireless in some cases, often suffer from limited functionality, fragile construction, or require external power sources and readers. The review concludes by pointing out that previous work focusing on customizable, modular, and reconfigurable soft electronics hasn't extensively translated to textile-based applications. The need for a universal platform and hardware-software integration for scalable, personalized smart clothing is highlighted.

The E-TeCS is developed by combining thin, customizable conformable electronic devices, including interconnect lines and off-the-shelf integrated circuits, with plastic substrates that are woven into knitted textile using high-throughput manufacturing. The system overview details the design of the suit, featuring channels for embedding flexible-stretchable electronic strips. The sensor integrated circuits and interconnects are fabricated using a two-layer industrial flexible printed circuit board (FPCB) process. Additional steps involve chip and passive component assembly and encapsulation with TPU and washable encapsulant. The tailored approach allows the suit to conform to the body's curvature. The modular sensor networks employ seven different modules: four temperature sensing modules, one inertial sensing module, and two interconnection modules. The temperature sensor (MAX30205) has an accuracy of 0.1°C and a resolution of 0.01°C. The inertial measurement unit (IMU) (MPU6050) measures 3-axis gyroscope and accelerometer data with high precision. These modules are interconnected using the I²C bus interface. The system can handle up to 128 sensor addresses, enabling the integration of multiple sensor types without cross-talk. A modular sensor network architecture is employed, where individual sensors are connected via interconnects and gathered by an external layer with a BLE module, microprocessor, and power source. A prototype demonstrates the scalability of the sensor-integrated fabric. The temperature and inertial sensors are characterized using IR thermography and FEM simulations. Seismocardiography (SCG) is used to measure the subtle motions around the body due to heart contractions. An IMU is placed below the sternum to detect both heart and breathing activities. The development of personalized E-TeCS involves digital knitting, a programmable automatic process that allows for the creation of custom textile channels for embedding the electronics. The resulting fabric is cut and sewn into a bodysuit. The pressure exerted by the E-TeCS on the skin is measured and modeled, showing that it's within the range of comfortable and accurate sensing. Testing of the serpentine interconnects is conducted using uniaxial stretching and fatigue testing to assess durability and electrical performance. Washability testing demonstrates the suit's suitability for daily wear, while breathability is assessed using standard methods. Finally, an activity test involving running at graded loads is conducted to demonstrate the E-TeCS's performance during physical activity. IR thermography is used for cross-validation of temperature data. Detailed explanations of sensor fabrication, digital knitting processes, E-TeCS tailoring and assembly, electromechanical testing, wireless communication and various data processing methods such as filter design are also included.

The E-TeCS successfully demonstrates large-scale, multimodal physiological sensing. The temperature sensor exhibits an accuracy of 0.1 °C and a precision of 0.01 °C. The accelerometer achieves a precision of 0.0012 m/s² for heart rate and respiration detection. The knit textile electronics withstand stretching up to 30% without significant degradation. The E-TeCS maintains functionality after repeated washing cycles. The suit achieves a comfortable compression pressure (2-20 mmHg) for optimal sensor-skin contact. The activity test shows the ability of the E-TeCS to simultaneously and wirelessly monitor 30 skin temperature nodes across the body during physical activity. The accelerometer data accurately reflects heart rate, respiration rate, and step counts during exercise. The temperature data aligns with expectations, showing changes related to exercise intensity and perspiration. FEM simulations successfully model the thermal and stress behavior of the sensor module and interconnects. The washability and breathability tests demonstrate the practical viability of the E-TeCS for real-world applications. The results also corroborate with IR thermography, further validating the accuracy of the temperature sensing data collected with the E-TeCS.

The findings demonstrate the feasibility and effectiveness of the E-TeCS for large-scale, multimodal physiological monitoring. The ability to simultaneously capture temperature, heart rate, respiration, and movement data provides a comprehensive understanding of physiological responses during dynamic activities. The high accuracy and precision of the sensor readings, coupled with the comfort and durability of the suit, address many limitations of previous wearable sensing technologies. The modular design and high-throughput manufacturing process makes the E-TeCS scalable and adaptable to various applications. The system's washability and breathability features further enhance its practicality for daily use. The correlation of the E-TeCS measurements with IR thermography validates the accuracy of the device and supports the successful implementation of the study methodology. The comprehensive data collected by the E-TeCS has the potential to significantly improve our understanding of human physiology during exercise and other dynamic activities, contributing valuable insights to healthcare, sports science, and other related fields.

This research successfully demonstrates a novel, tailored electronic textile conformable suit (E-TeCS) for large-scale spatiotemporal physiological sensing. The E-TeCS overcomes limitations of existing wearable technologies by combining high-accuracy sensing, comfortable design, scalability, and durability. Future work could focus on incorporating additional sensors and expanding the applications of the E-TeCS beyond the laboratory setting. The integration of more diverse sensing modalities, along with advanced data analysis techniques, would further improve the capabilities of this technology. The platform's versatility opens opportunities for personalized telemedicine and remote health monitoring across various environments and applications.

While the study demonstrates promising results, some limitations exist. The current prototype focuses on upper body sensing, and future versions could incorporate full-body coverage. The activity test was conducted with a single volunteer, and further testing with a diverse population is needed to assess generalizability. The long-term stability and durability of the E-TeCS under various environmental conditions also requires further investigation. Finally, the computational complexity for the data processing and real-time visualization could also be improved.