World’s Most Sensitive Flexible Strain Sensor Enables Real-Time Stroke Monitoring

Flexible and stretchable strain sensors are designed to detect biomechanical signals or measure deformation in objects by monitoring changes in the electrical resistance of conductive materials. However, current sensors struggle with low sensitivity and performance degradation when measuring very small strains, specifically those below 10−3. This limitation presents significant challenges, particularly in the early diagnosis of diseases linked to mechanical physiological signals, as well as in assessing structural reliability and conducting preemptive safety evaluations. For example, cerebrovascular conditions like brain hemorrhages or ischemia produce infinitesimal strains smaller than 10−3 before they become critical. Similarly, structural materials typically experience strains of 10−5 to 10−3 on their surfaces prior to catastrophic failure, which can result in substantial loss of life. Now, a groundbreaking study has introduced a hypersensitive, flexible, and stretchable sensor by combining microcracks with meta-structures in a novel way. This technology enables real-time stroke diagnosis through continuous blood flow monitoring, marking a significant advancement in precision biomedical engineering.

Researchers from Seoul National University College of Engineering (SNU, Seoul, Korea), in collaboration with other experts, have developed a strain sensor that outperforms existing sensors in sensitivity. The team incorporated a meta-structure with a negative Poisson's ratio, which enhanced the sensor's sensitivity by up to 100 times compared to previous versions. This new sensor can detect strains as small as 10−5, which corresponds to a length change comparable to a single atom on the surface of a human hair. The breakthrough in sensitivity was achieved by amplifying electrical resistance changes through the controlled widening of nanoscale microcracks. This approach enabled the sensor to monitor extremely small deformations, such as those occurring during microbial growth, like the real-time detection of strain caused by the growth of mold hyphae on bread, which generates strain as tiny as 10−5.

The sensor also shows immense promise for biological applications. The research team successfully attached the sensor to the surface of cerebral blood vessels inside the skull, enabling real-time monitoring of blood pressure and blood flow changes. This innovation highlights the sensor's potential for the early detection of cerebrovascular diseases, including cerebral hemorrhages and ischemia, as well as cardiovascular disorders, providing highly accurate medical data. Additionally, the sensor is made from biodegradable materials, which allows it to decompose naturally without leaving long-term residue in the body, ensuring patient safety and eliminating the need for further surgeries or side effects. The findings of this study, published in Science Advances, have drawn significant attention due to the combination of cutting-edge technology and its practical, real-world applications.

"This study is not merely about improving sensor performance, but about presenting a groundbreaking approach that overcomes the fundamental limitations of the previous technologies," stated the research team. "We anticipate wide-ranging applications not only in bioengineering and medical devices but also in fields such as robotics, disaster response, and environmental monitoring."

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