As human-machine interactions become more prominent, pressure sensors that can analyze and simulate human touch are likely to grow in demand, including those for prosthetic devices. A team of researchers from Penn State and Hebei University of Technology in China have developed a sensor they say is extremely sensitive and reliably linear over a broad range of applications, had high pressure resolution, and able to work under large pressure preloads. Due to the sensor’s large-scale production capability, the research team says the design and fabrication framework can be applied to design and demonstrate smart prosthetic interfaces, intelligent human-machine interfaces, and next-generation health-monitoring devices.
“The sensor can detect a tiny pressure when large pressure is already applied,” said Huanyu “Larry” Cheng, PhD, co-author of a paper on the work. “An analogy I like to use is it’s like detecting a fly on top of an elephant. It can measure the slightest change in pressure, just like our skin does with touch.”
Cheng, the James L. Henderson Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State, and his research team found that using a pressure sensor consisting of gradient micro-pyramidal structures and an ultrathin ionic layer to give a capacitive response was the most promising. The high sensitivity of the microstructures, however, would decrease as the pressure increased, and the random microstructures that were templated from natural objects resulted in deformation and a narrow linear range. Simply, when pressure was applied to the sensor, it would change the sensor’s shape, altering the contact area between the microstructures and throw off the readings.
To address this challenge, the scientists designed microstructure patterns that could increase the linear range without decreasing the sensitivity—essentially making it flexible, so it could still function with real-world pressures. Cheng credits Ruoxi Yang, a graduate student in his lab and first author of the study, as the driver of this solution.
“Yang is a smart student who introduced the idea to solve this sensor issue, which is something like a combination of many small pieces, smartly engineered together,” Cheng said. “We know the structure must be microscale and must have a delicate design. But it is challenging to design or optimize the structure, and she worked with the laser system we have in our lab to make this possible.”
Editor’s note: This story was adapted from materials provided by Penn State.
