DNA-inspired design enhances flexible fibre sensors

Researchers at Shinshu University in Japan have introduced a new design for more durable, flexible fibre sensors in wearables, inspired by the shape of DNA. Traditional fibre sensors have electrodes at both ends, which often fail under repeated movement when placed on body joints. The proposed double-helical design places both electrodes on one end, allowing the sensor to endure repeated stretching and movement, thereby addressing a key limitation of conventional wearable sensors.

Flexible fibre sensors are used in smart wearables, as their compact size and lightweight feel make them suitable for everyday use. However, current designs, commonly placed at joints, face limited applications due to mechanical challenges. Traditional fibre sensors with electrodes at both ends are vulnerable when applied to joints like fingers or knees, where repeated movement pulls on connecting wires, causing them to break loose or produce measurement inaccuracies.

To address this issue, the researchers developed a new sensor with a double-helical structure that mimics the shape of DNA. This new design places both electrodes on one end of the fibre, reducing strain during movement and improving durability. The research findings have been published in the journal Advanced Science.

“Effective electrode design is critical to the performance and lifespan of wearable sensors. But in one-dimensional fibre sensors, this has long been a challenge. Our design addresses this issue directly,” said Associate Professor Chunhong Zhu, the lead author of the study.

The researchers drew inspiration from the stability of DNA’s double helix, which is maintained by hydrogen bonds between complementary base pairs. In a similar fashion, they twisted two specially designed coaxial fibres together to create a tightly bound, stable structure. Each fibre is produced using coaxial wet spinning, with an insulating outer layer and a fluffy, conductive inner core. The core contains multi-walled carbon nanotubes (MWCNTs), while the outer layer includes thermoplastic polyurethane (TPU) and titanium dioxide (TiO₂) nanoparticles, which make the fibres fluffier and stronger.

After heat treatment, the two fibres form a double helix with built-in positive and negative terminals on the same end, eliminating the need for complex wiring at both ends — a common problem in traditional designs.

“The TT/MT dual-helical fibre has two electrodes at one end and a free end with no electrodes, greatly simplifying the wiring of flexible sensors,” said Ziwei Chen, co-author of the study.

The resulting TT/MT dual-helical fibre sensor measures less than 1 mm in diameter, making it easy to integrate into wearable textiles. It is also durable, enduring repeated stretching and bending. In laboratory tests, it withstood over 1000 stretching cycles and extended more than 300% beyond its original length without breaking.

With both electrodes located on the same side, the sensor can be used across joints with the side containing the electrodes attached to areas with limited movement, such as the back of the hand, cheeks or knees, without risking wire damage. This opens up applications for tracking finger gestures, facial expressions and gait movements, and even detecting breathing patterns during sleep.

The design also shows promise for use in Bluetooth-connected wearables, enabling real-time remote monitoring for rehabilitation and sports training, according to the researchers. These sensors could also be embedded in clothing for high-risk activities like mountaineering, where they could send emergency alerts in case of accidents, falls or health issues such as hypoxia.

With this novel design, the researchers hope to inspire the development of next-generation intelligent fibres that are durable and sensitive, while also being easy to integrate into daily wear.

“Our design strategy, exemplified by the TT/MT dual-helical fibre highlighted in our study, also provides a versatile approach that can inspire the development of various intelligent fibres tailored for different applications,” Zhu said.

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