Researchers from Ghent University have created what they believe may be the first optical circuit that uses bendable and stretchable interconnections. Formed from polydimethylsiloxane, or PDMS, the interconnects guide light along their path, even when stretched up to 30% or when bent around an object the diameter of a human finger.
"To our knowledge, this is the first truly bendable, stretchable optical link with these miniature dimensions," said Jeroen Missinne of Ghent University. While optical interconnections have been made from similar materials, no one had discovered a way to enable these materials to carry light while stretched. In the new method, the stretchable substance itself is the waveguide. The interconnect consists of two materials, both made of PDMS – a transparent core, through which the light travels; surrounded by another transparent layer of PDMS with a lower refractive index. This traps light in the guide's core, causing it to propagate along its length. "We were surprised that stretching had so little influence on the waveguides and that their mechanical performance was so good," Missinne said. The guide's reliability was also described as 'remarkable', with no degradation even after elongating it by 10% for 80,000 times. Light is launched into the interconnect using a vertical cavity surface emitting laser and detected using a photodiode. Now, the team plans to make their waveguide smaller, down from 50µm to just a few microns in diameter, which will require a redesign of the parts of the waveguide where light enters and exits. Potential applications for the interconnect include wearable body sensors, moving machine parts, robotic limbs and deformable consumer electronics. Pic: Centre for Microsystems Technology/imec/Ghent University.