A Breathable Knitted Fabric-Based Smart System with Enhanced Superhydrophobicity for Drowning Alarming

Wearable strain sensors have aroused increasing interest in human motion monitoring, even for the detection of small physiological signals such as joint movement and pulse. Stable monitoring of underwater human motion for a long time is still a notable challenge, as electronic devices can lose their effectiveness in a wet environment. In this study, a superhydrophobic and conductive knitted polyester fabric-based strain sensor was fabricated via dip coating of graphene oxide and polydimethylsiloxane micro/nanoparticles. The water contact angle of the obtained sample was 156 degrees, which was retained above 150 degrees under deformation (stretched to twice the original length or bent to 80 degrees). Additionally, the sample exhibited satisfactory mechanical stability in terms of superhydrophobicity and conductivity after 300 abrasion cycles and 20 accelerated washing cycles. In terms of sensing performance, the strain sensor showed a rapid and obvious response to different deformations such as water vibration, underwater finger bending, and droplet shock. With the good combination of superhydrophobicity and conductivity, as well as the wearability and stretchability of the knitted polyester fabric, this wireless strain sensor connected with Bluetooth can allow for the remote monitoring of water sports, e.g., swimming, and can raise an alert under drowning conditions.