A team at North Carolina State University has developed a soft stretchable strain sensor that combines high sensitivity, a large sensing range, and high robustness. It is capable of detecting even minor changes in strain with a greater range of motion than previous technologies.
Strain is a measurement of how much a material deforms from its original length. In the medical arena, strain measurement is useful in applications that measure blood pressure or physical movement. Previously, the challenge in creating sensitive strain sensors has been the balance between sensitivity and the range of stretch capability.
“The new sensor we’ve developed is both sensitive and capable of withstanding significant deformation,” says Yong Zhu, corresponding author of the paper. “An additional feature is that the sensor is highly robust even when over-strained, meaning it is unlikely to break when the applied strain accidentally exceeds the sensing range.”
This new sensor is made of a silver nanowire network embedded below the surface of an elastomer polymer strip. The polymers feature a series of parallel cuts of a uniform depth into the sides of the sensor in a distinct, alternating pattern. The patterned cuts enable a greater range of deformation without sacrificing sensitivity.
To demonstrate the sensor’s utility, the researchers created new health monitoring and human-machine interface devices, including: integration into wearable systems for monitoring physiological functions and body motions associated with different levels of strain; and a soft, three-dimensional touch sensor that tracks both normal and shear stresses to be used for human-machine interfaces and tactile sensing for robotics.
“The sensor can be easily incorporated into existing wearable materials such as fabrics and athletic tapes, convenient for practical applications,” Zhu says. “And all of this is just scratching the surface. We think there will be a range of additional applications as we continue working with this technology.”