Taking a lesson from spiders: Researchers create an innovative method to produce soft, recyclable fibers for smart textiles

Date:
July 10, 2023
Source:
National University of Singapore
Summary:
Researchers drew inspiration from the spider silk spinning process
to fabricate strong, stretchable, and electrically conductive
soft fibers.

Their novel technique overcomes the challenges of conventional
methods, which require complex conditions and systems. Such soft and
recyclable fibers have a wide range of potential applications, such
as a strain- sensing glove for gaming or a smart mask for monitoring
breathing status for conditions such as obstructive sleep apnea.


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FULL STORY ========================================================================== Smart textiles offer many potential wearable technology applications,
from therapeutics to sensing to communication. For such intelligent
textiles to function effectively, they need to be strong, stretchable,
and electrically conductive. However, fabricating fibres that possess
these three properties is challenging and requires complex conditions
and systems.

Drawing inspiration from how spiders spin silk to make webs, a team of researchers led by Assistant Professor Swee-Ching Tan from the Department
of Materials Science and Engineering under the National University of Singapore's College of Design and Engineering, together with their international collaborators, have developed an innovative method of
producing soft fibres that possess these three key properties, and at the
same time can be easily reused to produce new fibres. The fabrication
process can be carried out at room temperature and pressure, and uses
less solvent as well as less energy, making it an attractive option for producing functional soft fibres for various smart applications.

"Technologies for fabricating soft fibres should be simple, efficient and sustainable to meet the high demand for smart textile electronics. Soft
fibres created using our spider-inspired method of spinning has been demonstrated to be versatile for various smart technology applications
-- for example, these functional fibres can be incorporated into
a strain-sensing glove for gaming purposes, and a smart face mask
to monitor breathing status for conditions such as obstructive sleep
apnea. These are just some of the many possibilities," said Asst Prof Tan.

Their innovation was demonstrated and outlined in their paper that was published in scientific journal Nature Electronics on 27 April 2023.

Spinning a web of soft fibres Conventional artificial spinning methods
to fabricate synthetic fibres require high pressure, high energy input,
large volumes of chemicals, and specialised equipment. Moreover, the
resulting fibres typically have limited functions.

In contrast, the spider silk spinning process is highly efficient and can
form strong and versatile fibres under room temperature and pressure. To address the current technological challenges, the NUS team decided to
emulate this natural spinning process to create one-dimensional (1D)
functional soft fibres that are strong, stretchable, and electrically conductive. They identified two unique steps in spider silk formation
that they could mimic.

Spider silk formation involves the change of a highly concentrated protein solution, known as a silk dope, into a strand of fibre. The researchers
first identified that the protein concentration and interactions in
the silk dope increase from dope synthesis to spinning. The second
step identified was that the arrangement of proteins within the dope
changes when triggered by external factors to help separate the liquid
portion from the silk dope, leaving the solid part -- the spider silk
fibres. This second step is known as liquid-solid phase separation.

The team recreated the two steps and developed a new spinning process
known as the phase separation-enabled ambient (PSEA) spinning approach.

The soft fibres were spun from a viscous gel solution composed of polyacrylonitrile (PAN) and silver ions -- referred to as PANSion --
dissolved in dimethylformamide (DMF), a common solvent. This gel solution
is known as the spinning dope, which forms into a strand of soft fibre
through the spinning process when the gel is pulled and spun under
ambient conditions.

Once the PANSion gel is pulled and exposed to air, water molecules in the
air act as a trigger to cause the liquid portion of the gel to separate in
the form of droplets from the solid portion of the gel, this phenomenon
is known as the nonsolvent vapour-induced phase separation effect. When separated from the solid fibre, the droplets of the liquid portion are
removed by holding the fibre vertically or at an angle for gravity to
do its work.

"Fabrication of 1D soft fibres with seamless integration of all-round functionalities is much more difficult to achieve and requires complicated fabrication or multiple post-treatment processes. This innovative method fulfils an unmet need to create a simple yet efficient spinning approach
to produce functional 1D soft fibres that simultaneously possess unified mechanical and electrical functionalities," said Asst Prof Tan.

Three properties, one method The biomimetic spinning process combined
with the unique formulation of the gel solution allowed the researchers
to fabricate soft fibres that are imbued with three key properties --
strong, stretchable, and electrically conductive.

Researchers tested the mechanical properties, strength, and elasticity,
of the PANSion gel through a series of stress tests and demonstrated
that this remarkable innovation possessed excellent strength and
elasticity. These tests also allowed the researchers to deduce that
the formation of strong chemical networks between metal-based complexes
within the gel is responsible for its mechanical properties.

Further analysis of the PANSion soft fibres at the molecular level
confirmed its electrical conductivity and showed that the silver ions
present in the PANSion gel contributed to the electrical conductivity
of the soft fibres.

The team then concluded that PANSion soft fibres fulfils all the
properties that would allow it to be versatile and potentially be used
in a wide range of smart technology applications.

Potential applications and next steps The team demonstrated the
capabilities of the PANSion soft fibres in a number of applications,
such as communication and temperature sensing. PANSion fibres were sewn
to create an interactive glove that exemplified a smart gaming glove.

When connected to a computer interface, the glove could successfully
detect human hand gestures and enable a user to play simple games.

PANSion fibres could also detect changes in electrical signals that
could be used as a form of communication like Morse code. In addition,
these fibres could sense temperature changes, a property that can
potentially be capitalised to protect robots from environments with
extreme temperatures. Researchers also sewed PANSion fibres into a smart
face mask for monitoring the breathing activities of the mask wearer.

On top of the wide range of potential applications of PANSion soft fibres,
this innovative discovery earns points in sustainability. PANSion fibres
could be recycled by dissolving in DMF, allowing it to be converted back
into a gel solution for spinning new fibres. A comparison with other
current fibre- spinning methods revealed that this new spider-inspired
method consumes significantly lower amounts of energy and requires lower
volume of chemicals.

Further to this cutting-edge discovery, the research team will continue
to work on improving the sustainability of the PANSion soft fibres
throughout its production cycle, from the raw materials to recycling
the final product.

* RELATED_TOPICS
o Plants_&_Animals
# Spiders_and_Ticks # Extreme_Survival #
Animal_Learning_and_Intelligence
o Matter_&_Energy
# Spintronics # Textiles_and_Clothing # Nature_of_Water
o Computers_&_Math
# Spintronics_Research # Artificial_Intelligence #
Communications
* RELATED_TERMS
o Spider_silk o Neuron o Spider o Sleep_disorder o
Virtual_reality o Chaos_theory o Optic_nerve o Silk

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Source: Materials provided by National_University_of_Singapore. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Songlin Zhang, Yihao Zhou, Alberto Libanori, Yibing Deng,
Mingyang Liu,
Mengjuan Zhou, Hao Qu, Xun Zhao, Peng Zheng, You-Liang Zhu, Jun
Chen, Swee Ching Tan. Biomimetic spinning of soft functional fibres
via spontaneous phase separation. Nature Electronics, 2023; 6 (5):
338 DOI: 10.1038/s41928-023-00960-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230710113851.htm

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