Similar to the way spiders detect vibrations, a new biosensor can detect a range of biosignals, from pulse to breathing rates

Wearable sensors are becoming increasingly popular for biomedical applications such as health monitoring. Drawing inspiration from how spiders detect vibrations, researchers from Ajou University in South Korea have developed a sensor that can respond to a wide range of pressures. The sensor is a promising step toward the development of highly sensitive wearable health monitoring devices, allowing the detection of breathing patterns, muscle contractions, and pulse rate fluctuations.

Caption: The TUNES sensor detects pressure by mimicking how spiders detect vibrations, allowing for the detection of a wide range of biosignals. The sensor finds use as a highly sensitive wearable sensor for monitoring pulse rates, muscle contractions, and respiration.

Picture courtesy: Shutterstock

From the aircraft wings that were modeled after birds by the Wright brothers, to Japan’s famous bullet train that was inspired by the shape of a kingfisher's beak, mimicking the natural world has often led to breakthroughs that have improved people’s lives drastically.

Now, in a study published in npj Flexible Electronics, Associate Professor Daeshik Kang and his research team from Ajou University, South Korea, have added another engineering feat to the list. The team has developed Tunable, Ultrasensitive, Nature-inspired, Epidermal Sensor (TUNES), a biosensing technology that mimics the way spiders detect vibrations. “Flexible devices can sensitively measure physical stimuli such as strain, pressure, and vibrations. However, there is a tradeoff between the sensor's measurement range and sensitivity, requiring different sensors depending on the target signal,” remarks Dr. Kang.

Spiders have mechanosensory slit organs present in their legs, used to perceive movements in their environment. These slits contain nerve endings that are activated by vibrations. The unique feature of the slit organs is enabling the spider to adjust the sensitivity by changing the leg position. To detect prey, spiders stretch their legs, opening these slits to enhance sensitivity to smaller vibrations. However, to avoid predators, they bend their legs, compressing or closing the slits in order to only detect large forces.

To replicate this, the research team fabricated nanoscale cracks on a metallized polyimide film, mimicking the slits on the spider’s legs. Just the way spiders bend their legs to adjust slit openings, when bent by an external force, the sheet also undergoes changes in the opening of the cracks. This results in a modification to the film's electrical resistance, enabling the detection of a wide range of pressures, from 0.05 Pa–25 kPa.

“The TUNES' ability to adjust sensitivity through preset strain overcomes the traditional tradeoff between measurement range and sensitivity,” says Dr. Kang.

The sensor’s broad sensitivity to strains makes it extremely versatile in detecting small as well as large mechanical biosignals. For instance, when attached to the ribcage, the sensor responds to the changing volume of the chest cavity during breathing, to monitor respiration. Inspired by this, the research team used the sensor to detect muscle contractions and subtle changes in the pulse rate. They even applied machine learning to the pulse rate data, to automatically identify and diagnose health conditions.

These capabilities, explains Dr. Kang, make the sensor highly suitable as a wearable health monitoring system for blood pressure, heart rate, and even age-specific diagnosis. He elaborates, “We anticipate the ability to provide users with the convenience of instantly assessing their health status by measuring various physiological signals using only one sensor system at an affordable cost.”

Providing users with the convenience and affordability of instantly assessing their health status by measuring various physiological signals using only one sensor is what drove the team to conduct this research. The highly sensitive sensor allows for non-invasive blood pressure measurements on the wrist, which opens avenues for non-invasive blood pressure monitoring, thus reducing unnecessary surgical risks. What’s more, TUNES has already shown success for non-invasive pressure measurement in clinical trials, proving its practicality, versatility, and effectiveness.

We are confident that the team’s efforts will take this valuable biosensor to the masses, sooner rather than later!

Reference

*Corresponding authors’ email ids: Daeshik Kang (dskang@ajou.ac.kr); Bon-Kwon Koo (bkkoo@snu.ac.kr); Je-sung Koh (jskoh@ajou.ac.kr); Seungyong Han (sy84han@ajou.ac.kr)

About Ajou University

Founded in 1973, Ajou University has quickly grown to become one of the top universities in the Republic of Korea. With over 15,000 students and 50 research centers in diverse fields, Ajou University partakes in the largest national research and graduate education project funded by the Korean Ministry of Education. In line with its recently reformed vision, Ajou University’s goal is to change society by connecting minds and carrying out high-impact research to improve the welfare of people in and outside Korea.

Website: https://www.ajou.ac.kr/en/index.do

About Dr. Daeshik Kang from Ajou University

Dr. Daeshik Kang is an Associate Professor at the Multiscale Bio-inspired Technology (MOST) Lab, Mechanical Engineering Department, Ajou University, South Korea. He received his Ph.D. in Mechanical Engineering from Seoul National University in 2014. After earning his doctorate, he worked as a postdoctoral researcher at the University of Illinois at Urbana-Champaign until 2016. His current research interests include robotics, artificial intelligence-based reinforcement learning, and biomedical applications. He has authored around 60 research papers, which have received close to 5,000 citations.