Stretchable photonics under development, such as displays and tunable optical devices, require a conductive transparent layer that also stretches; however, the indium tin oxide (ITO) layer used in ordinary rigid displays is brittle and does not stretch.
A group at the Functional Materials and Microsystems Research Group and Micro Nano Research Facility, RMIT University (Melbourne, Australia) has come up with a way of using ITO in stretchable photonics; the researchers call their approach microstructure tectonics, or microtectonics.1 The group has also made the approach work with zinc oxide (ZnO), which is also ordinarily nonstretchable; ZnO can then potentially be used as a stretchable photodetector as well as an optical material.2
Metal oxide plates
In a stretchable microtectonic layer, microscopic rigid plates of the metal oxide are embedded in a stretchable organic matrix such as polydimethylsiloxane (PDMS); when the composite material is stretched, the plates slide over each other, maintaining conductive contact.
In an example of use of microtectonics in optics, a diffraction grating that spectrally tunes as it is stretched can detect displacements with nanometer accuracy.
When used as a light sensor, the composite can be made into a large-area skin patch that detects harmful UV radiation; the patch can also be made to detect gases.
REFERENCES:
1. Philipp Gutruf et al., Asia Materials (2013); doi: 10.1038/am.2013.41
2. Philipp Gutruf et al., Small (2015); doi: 10.1002/smll.201500729
This article was published by Laser Focus World on 6/10/2015