A fiber sensor inspired by the shape of DNA, developed by researchers at Shinshu University, introduces a new design for more durable, flexible fiber sensors in wearables. Traditional fiber sensors have electrodes at both ends, which often fail under repeated movement when placed on body joints. The proposed double-helical design, however, places both electrodes on one end, allowing the sensor to endure repeated stretching and movement, effectively addressing a key limitation of conventional wearable sensors.
Flexible fiber sensors are widely 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 application due to mechanical challenges. Traditional fiber 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 solve this issue, a team of researchers from Shinshu University, Japan, has developed a new type of flexible sensor with a double-helical structure that mimics the shape of DNA. This new design places both electrodes on one end of the fiber, reducing strain during movement and significantly improving durability. Their findings were published online on February 4, 2025, and in Volume 12, Issue 12 on March 27, 2025, in the journal Advanced Science.
“Effective electrode design is critical to the performance and lifespan of wearable sensors. But in one-dimensional fiber sensors, this has long been a challenge. Our design addresses this issue directly,” says Associate Professor Chunhong Zhu, the lead author of the study from the Institute for Fiber Engineering and Science.
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 fibers together to create a tightly bound, stable structure. Each fiber is produced using a method called 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 fibers fluffier and stronger.
After heat treatment, the two fibers naturally 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 fiber has two electrodes at one end and a free end with no electrodes, greatly simplifying the wiring of flexible sensors,” says Mr. Ziwei Chen, co-author of the study.
The resulting TT/MT dual-helical fiber sensor is remarkably slender, measuring less than 1 mm in diameter, making it easy to seamlessly integrate into wearable textiles. In addition, it proved to be highly durable, enduring repeated stretching and bending. In laboratory tests, it withstood over 1,000 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.
In one test, the researchers placed the sensor inside a glove and used a machine-learning model to help it learn how to recognize finger movements. The glove was able to identify six common hand gestures with 98.8% accuracy. In another test, the sensor detected how long each finger pull lasted and used that to send Morse code wirelessly, showcasing its potential as a tool for assisting people with disabilities.
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. The team envisions these sensors being 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 innovative design, the researchers hope to inspire the development of the next generation of intelligent fibers that are not only durable and sensitive but also easy to integrate into daily wear.
“Our design strategy, exemplified by the TT/MT dual-helical fiber highlighted in our study, also provides a versatile approach that can inspire the development of various intelligent fibers tailored for different applications,” says Dr. Zhu.
