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Page 10 of 16 Fan et al. Soft Sci 2024;4:11 https://dx.doi.org/10.20517/ss.2023.47

[53]
exhibits excellent impact resistance under different impacts . More recently, to enlarge its application, the
leather layer was treated by MXene nanosheets for functional design. The treated leather composite has
[54]
excellent conductivity and no reduced impact resistance , which can provide sensing feedback under
different impacts. Finally, an intelligent impact resistance device based on the wearable Leather/MXene/
SSG/NWF safeguarding leather composite was obtained by integrating a wireless transmission system;
therefore, the final system could monitor the impact status of the leather composite in real time
[Figure 5A]. In short, the development of intelligent leather composites opened up new avenues in the field
of intelligent protection.

Thermoregulatory clothing
Recently, many studies have reported the development of multifunctional textiles for intelligent
thermoregulation, which could maintain human body temperature in a comfortable area . Most animal fur
[76]
benefits from the low thermal conductivity brought by their multilayer and porous skin structure; thus, they
can effectively reduce heat loss and have a natural insulation effect . In this case, the most common use of
[37]
[5]
leather in daily life is in the field of clothing . It is worth noting that during sudden changes in weather or
harsh environments, a single insulation performance may not be able to meet the temperature needs of the
human body . Mo et al. developed an asymmetric double-layer leather composite. A porous cellulose
[77]
acetate layer achieved passive radiation cooling on the corium side, and a highly connected CNT network
exerted passive radiative heating and Joule-heating ability on the other side . The two different functions
[45]
can switch between cooling and heating modes according to environmental conditions by turning over two
sides of the fabric, thus achieving high adaptability to weather changes [Figure 5B]. Fan et al. designed a
conductive MXene array on a leather substrate, resulting in a leather vest that could achieve regional electric
[54]
heating . By controlling voltage, the leather vest could precisely regulate the temperature regulation, which
could be used to cope with extreme cold environments by providing the required temperature for the
human body [Figure 5C]. As a result, the above analysis demonstrates that the leather composites exhibit
enormous application potential in intelligent thermoregulatory clothing.

SOFT WEARABLE ROBOTICS FOR FUTURE APPLICATIONS BASED ON LEATHER
COMPOSITES
In recent years, soft wearable robotics has received increasing attention due to the rapid development of
flexible sensors and human-robot interface applications . Xiloyannis et al. developed a soft and textile-
[78]
based robotic exoskeleton for assisting hand opening and closing [Figure 6A] . Schmidt et al. introduced a
[79]
soft and wearable device to provide gravity support to the user’s knee and hip joints [Figure 6B] . These
[80]
resulting soft robotic devices based on textiles could help the wearer engage in simple daily activities.
Leather composites have good biocompatibility and natural fiber structure, but research on the application
of soft robots is scarce. Dong et al. prepared a smart conductive leather skin to imitate the functions of
human skin . Furthermore, a smart glove based on leather skin was designed to monitor complex hand
[50]
movements. At the same time, a human-computer interaction function has been developed based on the
smart glove, which can control the movement of the robotic arm in real time by using gestures [Figure 6C
and D]. A broad research foundation of leather composites has been built in intelligent applications.
Intelligent leather composites will expand their research gaps in the field of soft robots in the future by
combining their biocompatibility and mechanical strength. Ultimately, it is expected to develop soft robots
that can cope with different complex environments, such as biomimetic soft robots, radiation-resistant
robots, safety protection robots, etc.

CONCLUSION AND OUTLOOK
Natural leather has a unique multilayer structure and collagen fiber network, which is easy to combine with