Novel sensors could enable 'smart garments'

Scientists have integrated sensors in a wide range of fibres, including cotton and wool, an advance that could lead to smart textiles which can detect human motion.

Fabric coated with this technology could be used in future garments where the sensors are slipped into the soles of shoes or stitched into clothing for motion detection, said researchers from the University of Delaware in the US.

Carbon nanotubes give this light, flexible, breathable fabric coating impressive sensing capability, according to the study published in the journal ACS Sensors.

When the material is squeezed, large electrical changes in the fabric are easily measured.

One potential application of the sensor-coated fabric is to measure forces on people's feet as they walk.

This data could help clinicians assess imbalances after injury or help to prevent injury in athletes, researchers said.

"As a sensor, it is very sensitive to forces ranging from touch to tonnes," said Erik Thostenson, an associate professor at the University of Delaware.

Nerve-like electrically conductive nanocomposite coatings are created on the fibres using electrophoretic deposition (EPD) of polyethyleneimine functionalised carbon nanotubes.

"The films act much like a dye that adds electrical sensing functionality," said Thostenson.

"The EPD process developed in my lab creates this very uniform nanocomposite coating that is strongly bonded to the surface of the fibre. The process is industrially scalable for future applications," he said.

Researchers can add these sensors to fabric in a way that is superior to current methods for making smart textiles.

Existing techniques, such as plating fibres with metal or knitting fibre and metal strands together, can decrease the comfort and durability of fabrics, said Thostenson.

The nanocomposite coating developed by the group is flexible and pleasant to the touch and has been tested on a range of natural and synthetic fibres, including Kevlar, wool, nylon, Spandex and polyester.

The coatings are just 250 to 750 nanometres thick - about 0.25 to 0.75 per cent as thick as a piece of paper - and would only add about a gramme of weight to a typical shoe or garment.

The materials used to make the sensor coating are inexpensive and relatively eco-friendly, since they can be processed at room temperature with water as a solvent, researchers said.