Bifunctional Smart Textiles with Simultaneous Motion Monitoring and Thermotherapy for Human Joint Injuries

Abstract The motion detection and thermotherapy provides a convenient strategy for the diagnosis and rehabilitation assessment of joint injuries. However, it is still challenging to simultaneously achieve accurate joint motion monitoring and on‐demand thermotherapy. Herein, core‐sheath sensing yarns (CSSYs) is proposed and fabricated for excellent electrical and photothermal heating, which consists of carbon black (CB)‐coated nylon (sheath layer), silver‐plated nylon and elastic spandex yarns (core layer). The CSSYs demonstrates great joule heating performance, which reaches 75 °C at 2 V applied voltage. The good thermal management performance can be well maintained when weaving these yarns into bifunctional smart textile. Further, the optimized double‐ply CSSYs (DPCSSYs) with helically twisted structure possess several appealing sensing performance, including preferable strain sensitivity (0.854), excellent linearity (0.962), and superior durability (over 5000 cycles). The as‐woven bifunctional smart textile can provide instant and convenient thermotherapy to the injured joints, and simultaneously monitor the injury and recovery conditions of the joint. Therefore, the designed bifunctional smart textile can provide a promising route for developing next‐generation healthcare smart textile.

on the spindles, the number of spindles required for winding the yarn depended on the number of feeding spindles.
Fabrication of DPCSSYs: Two strands of CSSYs were coiled in parallel on a tube and twisted to form a DPCSSYs with a helical conformation.The density of the DPCSSYs could be effectively controlled by varying the fabrication parameters (twisting factor and winding speed).

Fabrication of CSSYs textile:
The CSSYs textile, using the SGA598-SD semiautomatic weaving loom, was woven with DPCSSYs as the weft yarn and CB-coated nylon as the warp yarn.
An INSTRON 5943 strength meter was used to measure the tensile properties of CSSYs.The relative capacitance changes in the CSSYs were measured using a capacitance meter (TH2638, Tong Hui Ltd., Changzhou City, China).The IR reflectivity and transmittance were measured using an FTIR spectrometer (Spotlight 200i, PerkinElmer) equipped with an infrared integrating sphere.Fourier transform infrared (FTIR) spectra were obtained using an FTIR instrument (Nicolet iS50, Thermo Fisher).UV-vis-NIR reflectivity and transmissivity were measured using a UV-vis-NIR spectrometer (UV-3600Plus, SHIMADZE) accompanied by an integrating sphere attachment.A passive radiative heating test was performed indoors; a heating plate was placed onto insulating foam, and the DC power (PPS3005S ATTEN) supply was connected to the heating plate at a power density of 70 W m -2 to keep the temperature of the heating plate around 36 °C.
The heating plate was then wrapped in the CSSYs textiles, and a thermocouple sensor (TS-08A SHSIWI) was used to measure the skin surface temperature under the textiles.Photothermal conversion tests were conducted outdoors in Wuhan, China.For the outdoor solar heating test, a solar power meter (TES1333R) was used to monitor the real-time solar intensity.A piece of thermally conductive tape was attached to insulating foam to simulate human skin, with a thermocouple sensor fixed onto the thermally conductive tape.The surface of the thermally conductive tape was covered with CSSYs textile.The insulating foam was attached to a melamine foam board for heat insulation.Joule heating performance was evaluated by applying DC voltage at both ends of the CSSYs.A thermocouple sensor (UT3208, UNI-T) was used to measure the temperature of the CSSYs.A G571 air permeability tester (Standard International Group (HK) pressure of 20 cm 2 S1.The thickness and area density of different textiles.Table S2.The comparison of sensing performance of CSSYs with reported flexible sensors.
and 200 Pa, respectively, according to GT/T 5453.The water vapor transmission rate of the various stretching textiles was tested by the upright cup method in which the size sample was 25 cm 2 , temperature was 38±0.6 °C, and relative humidity was 90±2 % based on ASTM E398.A thermocouple sensor (UT3208, UNI-T) was used to record the temperatures of CSSYs textiles artificial skin and the human body, respectively.The Noraxon Ultium EMG was employed to monitor electromyographic (EMG) signals before and after thermotherapy.Human participants gave permission for the collected data (physiological signal detection and motion tracking) to be used in this study via consent forms.The experimental protocols were approved by the Research Ethics Committee of Soochow University (grant number: 52173059) and informed consent form with signature was obtained from the volunteer for the human activity experiments.

Figure S1 .
Figure S1.The relationship between the electrical resistance of CSSYs and the number of core winding yarns.

Figure S2 .
Figure S2.Stretching of CSSYs at different strain levels, scale bar 1 cm.

Figure S3 .
Figure S3.The temperature curve and infrared image of CSSYs under a 2 V input voltage.

Figure S4 .
Figure S4.A large piece of fabric woven by CSSYs, scale bar 10 cm.

Figure S5 .
Figure S5.(a) Water vapor transmission rate and (b) air permeability of the CSSYs textile, cotton textile, GO-fabric and Mylar blanket.

Figure S6 .
Figure S6.The optical images demonstrate the flexibility, scalability, and stretchability of the CSSYs textile, scale bar 1 cm.

Figure S8 .
Figure S8.(a) Schematic of experimental setup for indoor passive radiative heating measurement.(b) Temperatures of the artificial skin covered with different textiles in an indoor environment with environmental temperature controlled at 16 ± 0.5 °C.

Figure S9 .
Figure S9.Absorptivity of CSSYs textile, cotton textile, GO-fabric, and Mylar blanket from ultraviolet to near-infrared wavelengths.The light red area represents the solar spectral irradiance.

Figure S10 .
Figure S10.The real-time solar intensity on the roof in Wuhan on November 10, 2022.

Figure S11 .
Figure S11.(a) Temperature of artificial skin covered with different textiles on a sunny day.(b) Digital images of real-time weather conditions at 9:00 AM and 9:00 PM on the sunny day and the corresponding thermal infrared images of different textiles.

Figure S12 .
Figure S12.Temperature curve of heating under 1 V from 11:00 AM and 9:00 PM in an outdoor environment.

Figure S14 .
Figure S14.Schematic cross-section illustration of DPCCSYs before and after stretching.

Figure S15 .
Figure S15.(a) Meshing and refinement of the simulation model on DPCSSYs.(b) The simulated stress generated at different strain levels.

Figure S16 .
Figure S16.(a) Force-strain curves of the DPCCSYs under various strains, (b) Force-strain curves of the DPCCSYs under 60% strain for 100 stretching-releasing cycles.

Figure S17 .
Figure S17.Testing system for sensing performance of DPCCSYs.

Figure S18 .
Figure S18.Relative capacitance changes of DPCSSYs with varied the number of core yarns.

Figure S24 .
Figure S24.Application demonstrations of DPCSSYs in human motion monitoring.

Figure S25 .
Figure S25.(a) Lifting plan and schematic illustration and (b) weaving process for the large-scale fabrication of the bifunctional smart textile.(c)The photographs of the bifunctional smart textile.

Figure S26 .
Figure S26.Multi-channel monitoring of various elbow movements with the bifunctional smart textile (a) before and (b) after thermotherapy.

Figure S27 .
Figure S27.The EMG of the human (a) knee and (b) shoulder before and after thermotherapy.