News Release

Underwater movement sensor alerts when a swimmer might be drowning

Peer-Reviewed Publication

American Chemical Society

Underwater movement sensor alerts when a swimmer might be drowning

image: An underwater movement sensor attached to a motorized swimming doll’s knee alerts a smartphone app when the doll stops kicking, simulating a swimmer in distress. view more 

Credit: Adapted from ACS Nano 2022, DOI: 10.1021/acsnano.2c08325

Many flexible fitness trackers can’t be submerged in water because the coatings required to completely seal these devices would make them uncomfortable to wear. Now, researchers reporting in ACS Nano have applied a thin, slippery coating to conductive fabric, creating a breathable underwater movement sensor. They integrated the sensor into a smart device that wirelessly alerts a smartphone app when a swimmer stops moving, an indication that they could be drowning.

Underwater movement sensors could have many applications, such as monitoring heart rate and tracking swimmers’ activity and safety. However, current methods to protect these electronics make the devices thick and impermeable to air, which could lead to skin irritation. Previous research, though, has shown that thin, even layers of polydimethylsiloxane (PDMS) provide enough water repulsion to protect flexible movement sensors underwater, but it’s unclear whether the coating would be comfortable. So, Jianying Huang, Cheolmin Park, Yuekun Lai and colleagues wanted to test PDMS as a water-repellent coating for a fabric-based sensor that would be part of a wireless underwater movement detection system.  

To do this, the researchers dipped a piece of polyester knit fabric into a graphene oxide solution and then into hydroiodic acid. The last immersion was into a solution containing PDMS microparticles and nanoparticles. Initial tests showed that the coated fabric was conductive and water-repellent, yet still permeable to air, suggesting that the material would be comfortable to wear. When a sample of the coated fabric was attached to a person’s finger that was then bent while underwater, it produced a measurable electrical response.

The team combined the fabric-based sensor with a power supply and a data collector to create a smart underwater movement system that could wirelessly transmit the electrical response to a smartphone app. When the smart device was attached to a motorized swimming doll, the app tracked the doll’s kicking legs. To simulate a swimmer in distress, the doll’s kicking motion was turned off, and the app sent a red warning message. The researchers say that because the smart movement sensor repels water, it could help monitor swimmers’ safety and be used in other types of underwater sensors. 

The authors acknowledge funding from the National Natural Science Foundation of China, the Natural Science Funds for Distinguished Young Scholars of Fujian Province, the Natural Science Foundation of Fujian Province, the 111 Project, the China National Textile and Apparel Council Key Laboratory of Flexible Devices for Intelligent Textile and Apparel, Soochow University, the State Key Laboratory of New Textile Materials and Advanced Processing Technologies, and the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF).

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

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