Ionically conductive silk fibers for smart fabrics

Update time : 2024-04-21 11:33:43

With the rise of smart wearable devices, people are committed to developing smart textiles with sensing functions similar to human skin. However, so far, smart sensing textiles that can sense external dangers, specifically identify and accurately locate human finger touches have yet to be realized.

To achieve this goal, the team prepared silk-based ionic hydrogel (SIH) fibers with excellent mechanical and electrical properties, and based on this, designed an intelligent sensing textile that can quickly respond to external dangers, such as fire, water, etc. It can protect the human body/robot from being scratched by immersion and sharp objects; at the same time, it has also designed sensing textiles that can specifically identify and accurately locate human finger touch, so that it can be used as a flexible wearable human-computer interaction interface. To assist people to control remote terminals conveniently. SIH fibers prepared by continuous wet spinning and solvent exchange have excellent breaking strength (55 MPa), ductility (530%), and stability due to their internal semi-crystalline, highly oriented structure and the addition of ionic liquids. And excellent electrical conductivity (0.45 S·m–1). Fabrics designed based on this fiber show important application potential in fields such as smart wearable devices and flexible human-computer interaction interfaces.

Preparation of SIH fiber by wet spinning + solvent exchange method

Preparation process, morphology, weavability and flexible electrical applications of SIH fibers.

Composition and structural characterization of SIH fiber

Thermogravimetric analysis, energy dispersive spectroscopy (EDS) and infrared spectroscopy confirmed that [Emim]BF4 was uniformly distributed in the SIH fiber. The weight loss at 350°C in the thermogravimetric curve is attributed to [Emim]BF4. The element F in the EDS spectrum belongs to [Emim]BF4. The peak at 1169 cm–1 in the infrared spectrum can be attributed to the asymmetric vibration of C−N−C in the [Emim]+ ring. At the same time, infrared spectra and polarizing microscope pictures proved the semi-crystalline structure and highly oriented structure of SIH fibers.

Mechanical and electrical properties of SIH fibers

SIH fibers exhibit excellent mechanical and electrical properties. Its tensile strength and elongation at break reach 4 MPa and 530% respectively. Further drawing treatment (before solvent exchange) can increase its tensile strength to 55 MPa, which is several times higher than previously reported hydrogel fibers (<10 MPa). Its ionic conductivity can reach 0.45 S·m–1 and remains stable after being placed for 3 weeks or under various mechanical stimuli (pressing, bending, stretching).

Specific recognition of danger signals by SIH fibers
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The electrical response and mechanism of SIH fibers to fire, water and sharp objects, demonstrating potential applications in identifying hazards.

A smart protective glove for bionic robotic hands was designed by integrating SIH fibers into commercial gloves. When exposed to hazardous conditions (fire, water and sharp objects), smart gloves generate characteristic electrical signals to accurately identify these hazards.

Touch sensing application of SIH fiber-based fabrics

Furthermore, by using SIH fibers, we designed fibers and fabrics that can specifically identify and accurately locate the touch of human hands. SIH fiber-based fabrics were first prepared: individual SIH fibers were integrated onto commercial fabrics or woven into plain weaves. Through the design of the circuit system, the point or area touched by the human hand can be specifically identified and accurately located, which makes it different from piezoresistive or capacitive sensing fabrics that respond to any object contact/press. When people wear fabrics made of SIH fibers, they can control remote terminals by touching them.