Scientists from the UK’s Bangor and Oxford universities have created a bio-superlens using spider silk, which may provide a new solution to integrating optics in biological systems.
Recently, it was discovered that transparent microspheres and cylinders can function as a super-resolution lens to focus light beyond the diffraction limit. A number of high-resolution applications based on these lenses have been demonstrated successfully and span nanoscopy, imaging, and spectroscopy. Fabrication of these superlenses, however, is often complex and requires sophisticated engineering processes.
‘We have proved that the resolution barrier of the microscope can be broken using a superlens, but production of manufactured superlenses invovles some complex engineering processes which are not widely accessible to other reserchers,’ commented Dr Zengbo Wang, who led the researcher team. ‘This is why we have been interested in looking for naturally occurring superlenses provided by “Mother Nature”, which may exist around us, so that everyone can access superlenses.’
An easier model candidate, such as a naturally occurring superlens, has been highly sought after.
In a paper published in Nano Letters on 17 August, the Bangor research team, in collaboration with Professor Fritz Vollrath’s silk group at Oxford University’s Department of Zoology, reported on a biological superlens provided by nature: the minor ampullate spider silk spun from the golden web spider (Nephila edulis). This natural biosuperlens can distinctly resolve 100nm features under a conventional white-light microscope with peak wavelength at 600nm, attaining a resolution of λ/6 that is well beyond the classical limit.
This is the first time that a naturally occurring biological material has been used as a superlens. The work opens new doors for the development of biology-based optical systems that may provide a new solution to integrating optics in biological systems.
The lenses could be used for seeing and viewing previously ‘invisible’ structures, including engineered nano-structures and biological micro-structures, as well as native germs and viruses.
The natural cylindrical structure at a micron- and submicron-scale make silks ideal candidates for use as lenses – in this case, the individual filaments had diameters of one tenth of a thin human hair. The spider filament allowed the group to view details on a micro-chip and a blue-ray disk, which would have been invisible using an unmodified optical microscope.
In much the same way as when you look through a cylindrical glass or bottle, where the clearest image only runs along the narrow strip directly opposite the line of vision – or resting on the surface being viewed – the single filament provides a one dimensional viewing image along its length.
‘The cylindrical silk lens has advantages in the larger field-of-view when compared to a microsphere superlens,’ Wang explained. ‘Importantly, for potential commercial applications, a spider silk nanoscope would be robust and economical, which in turn could provide excellent manufacturing platforms for a wide range of applications.’
Bangor University’s School of Electronic Engineering