Sensing it all

North Carolina State University, US, has developed a technique for creating sensors that function in air and water, writes Nick Flaherty.

Researchers used a sensitive strain sensor, sandwiched between two thin films of a highly elastic, waterproof polymer.

The polymer encapsulates the sensor to keep water out, but it does not restrict the movement of the material. This gives the sensor the desired sensitivity and stretchability, and it can be connected to a small chip that transmits data wirelessly.

The conductive layer, made of silver nanowires embedded below the surface of polydimethylsiloxane, was sandwiched by two layers of thermoplastic polyurethane. Periodic sharp cuts were introduced to change the direction of flow from across the sensor to along the conductive path defined by the opening cracks. The crack advancing and opening is controlled by a combination of weak/strong interfaces within the sandwich structure.

The strain sensor showed a high gauge factor up to 289, a linear sensing response, a fast response time of 53 ms, and stability after 16,000 loading cycles and 20 days in an aqueous saline solution.

UPCOMING EVENTS