Friday, September 22, 2023

Researchers develop iontronic sensor that simulates human touch

Researchers from Penn State and the Hebei University of Technology have developed a highly sensitive sensor capable of detecting subtle pulses, operating robotic limbs, and creating ultrahigh-resolution scales at the same time it is cost-effective.

The researchers wanted to create a sensor that would be highly sensitive and reliably linear over a wide range of applications, have a high-pressure resolution, and be able to operate under large pressure preloads.

After trying many different approaches, they found that using a pressure sensor with gradient micro-pyramidal structures and an ultrathin ionic layer to provide a capacitive response was the most promising.

However, when pressure is applied to the sensor, it will change the shape of the sensor and thus change the contact area between the microstructures and throw off the reading.

To address these challenges, the researchers designed microstructure patterns that could increase the linear range without decreasing the sensitivity. They basically made it flexible, so it could still function in the gradience of pressures that exist in the real world.

Researchers explored the use of a CO2 laser with a Gaussian beam to create programmable structures such as gradient pyramidal microstructures (GPM) for iontronic sensors, which are soft electronics that can mimic the perception functions of human skin.

This process reduces the cost and process complexity compared with the photolithography method, which is commonly used to prepare delicate microstructure patterns for sensors.

“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,” said Huanyu “Larry” Cheng, James L. Henderson Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State.

The researchers tested the iontronic sensor by detecting microscopic pulses, operating an interactive robotic arm, and building ultra-high-resolution, smart weighing scales and chairs. They found that it had had a rapid response and recovery times and excellent repeatability.

The researchers also found that the proposed fabrication approach and design toolkit in this work can be used to easily tune pressure sensor performance for various target applications. It provides opportunities to fabricate other iontronic sensors, the range of sensors that use ionic liquids such as an ultrathin ionic layer.

Besides enabling future scales that will make it easier for parents to weigh their babies, these sensors will also have other uses.

According to researchers, they have been able to detect pulses not only from the wrist but also from other distant vascular structures such as the eyebrows and fingertips.

Additionally, they combine it with a control system to show that it is possible to use it for the future of human-robotic interaction. The researchers envision other healthcare uses, such as when someone has lost a limb, and this sensor could be part of a system to help them control a robotic limb.

This optimized sensor could potentially be used in various applications, such as a sensor to measure a person’s pulse in high-stress work situations, such as search and rescue after an earthquake or performing difficult and dangerous tasks at a construction site.

Journal reference:

  1. Ruoxi Yang, Ankan Dutta, Bowen Li, Naveen Tiwari, Wanqing Zhang, Zhenyuan Niu, Yuyan Gao, Daniel Erdely, Xin Xin, Tiejun Li, and Huanyu Cheng. Iontronic pressure sensor with high sensitivity over ultra-broad linear range enabled by laser-induced gradient micro-pyramids. Nature Communications, 2023; DOI: 10.1038/s41467-023-38274-2