A new type of thin wearable sensor for people with disabilities could turn a hand, finger, or facial movement into a communication—no voice or touchscreen required.

The sensor could open new possibilities for rehabilitation applications and helping those with disabilities communicate more easily, say researchers in Beijing Normal University in China. The sensor was designed to be comfortable for long-term wear and detecting movements with high accuracy.

Communicating via gestures or facial expression

“For someone recovering from a stroke, these sensors could monitor wrist, finger or even facial movements to monitor their rehabilitation progression,” said researcher Kun Xiao. “For individuals with severe mobility or speech impairments, the sensors could translate gestures or facial expressions into words or commands, enabling them to communicate with others or interact with technology more easily.”

The sensors combine a soft, flexible material called polydimethylsiloxane (PDMS) and an optical fiber Bragg grating (FBG). According to a cross-disciplinary team of researchers in optical, biomedical, software and electrical engineering from Beijing Normal University, the sensors showed a high level of sensitivity and accuracy during tests involving gesture recognition and communication assistance.

Fitness, athletics, health uses

The researchers note that the sensors could [also] be tailored for applications such as monitoring other health indicators like respiratory or heart rate by detecting subtle body movements, and for athletes or fitness enthusiasts to monitor and improve their form or technique in real time or be integrated into gaming systems for more immersive and interactive experiences.

Personalized assistive technologies

This new work is part of a larger project aimed at developing innovative assistive technologies and was inspired by the challenges faced by people with disabilities and those recovering from conditions like strokes, who often struggle with basic movements and communication.

“Traditional methods are either too cumbersome, lacked accuracy or weren’t versatile enough to cater to individual needs,” said Zhuo Wang from Beijing Normal University. “Our goal was to develop a wearable solution that was both precise in detecting gestures and comfortable for everyday use, offering a more personalized and adaptive approach to rehabilitation and assistance.”

Flexible, skin-friendly materials

To do this, the researchers created patches made from PDMS, a type of silicone elastomer that is very flexible and skin friendly. This allows people to wear them for long periods without irritation or discomfort. To give the patch its movement-sensing capability, the researchers embedded the PDMS with FBGs, a type of reflector that is etched into a short segment of optical fiber to reflect specific light wavelengths while transmitting all the others.

“We found that using a thicker PDMS patch caused a more pronounced wavelength shift. Leveraging this sensitivity-enhancing effect of PDMS allows these optical sensors to detect even the slightest bend of a finger or twist of a wrist,” said Chuanxin Teng from Guilin University of Electronic Technology.

The sensors can be applied to various parts of the body for a wide range of applications. A precise calibration method allows the sensors to be tailored to each user, making them adaptable to various applications.

Transforming movement into communication

To demonstrate the capabilities of their PDMS-embedded wearable FBG sensors, the researchers conducted a series of tests focusing on gesture recognition and communication assistance. After calibrating the sensors for individual participants, they attached the sensors to different parts of the body, such as the wrist and fingers, to detect various movements.

They also developed a system that enabled the sensors to translate simple gestures into commands or messages. For example, they used finger movements to spell out words based on Morse code.

For both tests, the sensors demonstrated a high level of sensitivity and accuracy in recognizing a wide range of gestures and translated them into words, showing their potential as an assistive technology for individuals with speech or mobility impairments.

Improvements

The researchers plan to make the sensor system smaller and more integrated so that it can be easily worn, as well as enhance the sensors’ ability to communicate wirelessly with smartphones, computers or medical devices, and to make sure they can withstand daily wear and tear, including exposure to moisture, heat and stretching.

This will allow users to interact with the technology and help caregivers or medical professionals monitor progress or data in real-time.

Citation: K. Xiao, Z. Wang, Y. Ye, C. Teng, R. Min, “PDMS-embedded wearable FBG sensors for gesture recognition and communication assistance,” Biomed. Opt. Express, Vol. 15, Issue 3, pp. 1892-1909 (2024). (open-access) https://doi.org/10.1364/BOE.517104

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