A tailored, electronic textile conformable suit for large-scale spatiotemporal physiological sensing in vivo

Abstract

The rapid advancement of electronic devices and fabrication technologies has further promoted the field of wearables and smart textiles. However, most of the current efforts in textile electronics focus on a single modality and cover a small area. Here, we have developed a tailored, electronic textile conformable suit (E-TeCS) to perform large-scale, multimodal physiological (temperature, heart rate, and respiration) sensing in vivo. This platform can be customized for various forms, sizes and functions using standard, accessible and high-throughput textile manufacturing and garment patterning techniques. Similar to a compression shirt, the soft and stretchable nature of the tailored E-TeCS allows intimate contact between electronics and the skin with a pressure value of around ~25 mmHg, allowing for physical comfort and improved precision of sensor readings on skin. The E-TeCS can detect skin temperature with an accuracy of 0.1 °C and a precision of 0.01 °C, as well as heart rate and respiration with a precision of 0.0012 m/s² through mechano-acoustic inertial sensing. The knit textile electronics can be stretched up to 30% under 1000 cycles of stretching without significant degradation in mechanical and electrical performance. Experimental and theoretical investigations are conducted for each sensor modality along with performing the robustness of sensor-interconnects, washability, and breathability of the suit. Collective results suggest that our E-TeCS can simultaneously and wirelessly monitor 30 skin temperature nodes across the human body over an area of 1500 cm², during seismocardiac events and respiration, as well as physical activity through inertial dynamics.

Keywords: Electrical and electronic engineering; Sensors and probes.

Fig. 1. A tailored, electronic textile conformable suit (E-TeCS) for distributed sensing wirelessly.

Illustration of (a) spatiotemporal sensor mapping of the body with temperature and accelerometer (heart beat and respiration), (b) textile channel for embedding flexible-stretchable electronic strips, and (c) exploded view of a sensor island. A photograph of final E-TeCS prototype (d) showing its conformability to the wearer (scale bar: 10 cm), (e) bare flexible-stretchable electronic strip (right) and woven electronic strip in a knit textile (left) (scale bar: 1 cm). Microscopy image of a (f) temperature (left), accelerometer (right, scale bar: 3 mm), and (g) interconnect modules (scale bar: 2 mm), and (h) cross-sectional view of an E-TeCS module embedded in a polydimethylsiloxane (PDMS) layer (scale bar: 2 mm).

Fig. 2. Thermal characterization of temperature sensor-embedded fabric.

The photography of (a) the hot-plate setup and thermal image between bare temperature sensor and the one integrated in a fabric (scale bar: 3 cm). b Characterization, simulation, and calibration results of the IR camera thermal test. c FEM thermal distribution for a source temperature of 34 °C. Simultaneous measurement of accelerometer SCG with a commercial ECG. d Mechano-acoustic response of accelerometer embedded in a fabric for 1 min. A.U.: arbitrary unit. e Magnified view of heart acoustic signals in (d), MC, mitral valve closure; AO, aortic valve opening; RE, rapid ventricular ejection; AC, aortic valve closure; MO, mitral valve opening; RF, rapid ventricular filling. f A commercial ECG response under 1 min. g Magnified view of the ECG response in (f). h Commercial accelerometer and (i) Zephyr Biopatch respiratory waveform. A.U.: arbitrary unit, and (j) Zephyr Biopatch and fabric accelerometer sensor placement (scale bar: 10 cm).

Fig. 3. Customized fabrics through digital knitting.

Photography of a (a) two-bed knitting machine (scale bar: 50 cm). b Screen capture of digital knitting software interface. c The structure of the customized fabrics in visual programming, the stripes correspond to hollow two-layer fabrics, and the checkered pattern represents interlocking mechanism. d Sketch of a single jersey knit loop structure (left) and interlocking loop structure (right). e A photograph of the E-TeCS fabric channels (scale bar: 1 cm). f Final prototype image of a E-TeCS (scale bar: 8 cm) with (g) exploded view of the detachable main processing and communication module (scale bar: 2 cm), h Experimental and modeled value of the compression pressure across the circumferences of the arm, as illustrated in (i). i A photograph of compression test for E-TeCS in ten different locations (scale bar: 5 cm).

Fig. 4. Electrical, mechanical testing, and modeling of interconnects.

a Instron result of a single uniaxial stretching test until rupture. b Time response and its (c) magnified view of fatigue cyclic test with a strain of 30%. d Image of serpentine interconnects throughout various strain value (scale bar: 2 cm), e FEM stress distribution of a serpentine interconnect, and (f) Zoomed-in views of stress distribution in (e). Real-time washing test. g Photograph of the sensorized fabric connected to a BLE system in a sealed, floating chamber (scale bar: 3 cm). h Photograph of test setup image. i Graph of temperature and (j) accelerometer data during the entire washing test.

Fig. 5. Physical exercise, spatiotemporal physiological mapping, and movement analysis.

a Photograph of a subject performing the physical exercise task wearing a E-TeCS. b Timeline of four separate sections of the physical exercise task. c Sensor mapping and body heat-map of the subject throughout the exercise. d Full-body and each section of the body skin temperature, and (e) anterior skin temperature sensor data during the exercise. All 3-axis accelerometer data (f) throughout the entire task. (g) in the middle of a graded load test at 6 mph. Raw z-axis sensor reading (h) before and (i) after the exercise.