Page 49 - Read Online

Wei et al. Soft Sci 2023;3:17 https://dx.doi.org/10.20517/ss.2023.09 Page 21 of 38

[181]
textile based on laser scribing technology . Through graphene oxide (GO) drop-casting, laser-scribing,
GO removal, and thermal transfer processes, an item of clothing with a multifunctional graphene device has
been obtained. This clothing contained a strain sensor, actuator, and ECG electrode, allowing the healthcare
monitoring clothes to monitor pulse, ECG, body motion, and people’s voices, as shown in Figure 9D.

Motion recognition
In the field of exercise healthcare, motion recognition is important to protect athletes from injury. By
monitoring and analyzing joint activities [54,94,182] , body posture , and micro movements [184-186] of users, the
[183]
system can analyze their physical conditions in real time and provide a necessary warning. In the field of
medical health, motion recognition can also be used for first-aid training . Due to the inflexible
[187]
mechanical characteristics of traditional sensors, it can be challenging to miniaturize and lighten motion
recognition devices; however, textile sensors can effectively solve this problem.

Human activities are mainly carried out through various joints, such as knee activities during running and
elbow joint activities during fetching; therefore, monitoring the activities of the main joints can help
recognize most human motions. Wu et al. designed a highly integrated TENG by injecting liquid alloy and
[94]
silicone rubber into a coaxial needle . This liquid alloy/silicone rubber core/shell structure has better
stability and higher sensitivity. Based on this TENG, they developed wearable devices such as wristbands
and kneepads to monitor the activities of joints. When joints bend, sensors attached to them detect the
activity and then translate it to electrical potential, as shown in Figure 10A. In addition, the simple
manufacture makes it possible for mass production, which makes it possible to put on the consumer
electronics market. Jiang et al. developed a stretchable, breathable, and stable nanofiber composite based on
perovskite/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and styrene-ethylene-butylene-
styrene (SEBS) . Based on this composite, a textile-based triboelectric nanogenerator was designed through
[54]
screen printing and electrospinning. This TENG has high sensitivity, searchability, and breathability and
can be used in motion-recognizing devices such as kneepads, insoles, and elbow pads, as shown in
Figure 10B. These sensors can also be attached to clothes and trousers, collecting joint motion and
producing electrical signals to monitor joint activities throughout the day. Moreover, Li et al. developed a
textile-based strain sensor by using sliver-coated yarn and nylon-wrapped spandex for the re-design layout
of the textile . The sensor provides a wide sensing range, and it can be strained up to 120%. They
[182]
developed a motion-monitoring kneepad based on the sensor to collect activities of the knee during
walking, running, and other exercises. Notably, it can collect more data than other flexible sensors based on
its 3D sensing ability. Data collection and processing allow for the analysis of people’s exercise habits and
the provision of appropriate exercise advice, as shown in Figure 10C.

Human motion is not only related to joint activities but also related to the posture of the human body. The
body posture determines the initial state and movable range of human motion. Therefore, monitoring
human body posture and the force of the body surface can better monitor the state of body activity and can
identify the potential risk of sports injury. Luo et al. used low-cost piezoresistive coating conductive wire to
[183]
create a coaxial fiber by scalable and automated fabrication process . Then, through the machine knitting
process, they developed the textile-based stress sensors array, in which each pair of fibers are orthogonally
overlapped to create a stress sensor unit. This sensor array can be used to collect pressure distribution
information of large areas such as the plantar, back, or abdomen for posture analysis. Moreover, Lan et al.
provided a stretchable fiber-shaped TENG (FTENG) for a wearable cardiopulmonary resuscitation training
system . The stretchable FTENG was obtained by coating silicon rubber and AgNWs ink on PU fiber, and
[187]
it performed effectively in energy collecting during the stretch. They developed a wearable cardiopulmonary
resuscitation training system based on the FTENG, which can monitor gestures during chest compression
for cardiopulmonary resuscitation and recognize interruptions in chest compression.