Fabric of communication

Soldiers on covert operations could discreetly communicate from a greater distance with new body-worn antennas being developed by UK researchers.

The team, including Darren Southee from Brunel University, is investigating methods for printing metal structures on cloth that is light and foldable. The results of this project could improve the performance of wearable antennas for applications including battlefield communications.

Southee said wearable antenna technology is still in its early stages, and the researchers hope their next-generation version will have greater range while using less power. One of the challenges will be to replace the copper that is normally used to make antennas.

'Copper is a great conductor and its material properties make it an excellent antenna,' he said. 'However, printing copper onto a fabric compromises that performance. A fabric is different to the FR-4 you would use for copper printed circuit boards.'

Southee said the method for printing the antennas puts various restrictions on the kind of material that could be used.

'If we use offset lithography, the rheological requirements of inks that you use are quite restrictive,' he added.

Southee explained that offset lithography is not like other types of printing where an image is created through relief. It is a chemical process that relies on ink that is hydrophobic and thixotropic, which is a fluid that changes its viscosity over periods of stress.

Southee added there are ways of making coloured inks that are hydrophobic and thixotropic. However, he said it is more challenging to make conductive inks with the same properties.

Southee has been able to demonstrate, through previous research, methods for printing conductive tracks in paper. The results have earned interest from companies including Hallmark UK for use in audio greeting cards.

Siobhan Wagner