Sprayable sensors to detect structural health

1 min read

Nanocomposites-inspired sensors have been developed by a Hong Kong Polytechnic University (PolyU) research team which can be sprayed directly on flat or curved engineering structural surfaces – such as train tracks and aeroplane structures – to render real-time information on their health status.

Due to the sensors’ light weight and low fabrication cost, the researchers claim large quantities could be deployed in a sensor network for detecting hidden flaws of structures.

"This nanocomposite sensor has blazed a trail for implementing in-situ sensing for vibration, or ultrasonic wave-based structural health monitoring, by striking a balance between sensing cost, and 'sensing effectiveness' – the quantity of data acquired by the sensors," said Professor Su Zhongqing.

An ultrasound actuator emits guided ultrasonic waves (GUWs), which the sensors receive and measure. If damage, such as a crack, is present in the structure, propagation of GUWs will be interfered by the damage, leading to unique wave scattering phenomena, to be captured by the sensor network.

Each sensor is connected to a network via a wire printed on the structure. By analysing and comparing the electrical signals converted from the electric resistivity, the network can spot the defect in a structure, as well as translate the signals into 3D images.

According to the researchers, the sensor can measure an ultrasound signal from static to up to 900kHz for the detection of cracks as small as 1 to 2mm in most engineering materials. They also claim that the response frequency is more than 400 times higher than the frequency of currently available nanocomposite sensors.