Interfacial properties/functions of the gecko skin. Courtesy of Gregory S. Watson and Jolanta A. Watson.Tiny hairs on geckos’ feet allow them to adhere to almost anything, but these outstanding climbers also have remarkable skin, according to new research. A team of scientists from University of the Sunshine Coast, James Cook University, and The University of Queensland in Australia, University of Hong Kong, and the University of Oxford has found that geckos’ skin is moisture-resistant, self-cleaning, and antibacterial [Watson et al., Acta Biomaterialia (2015), http://dx.doi.org/10.1016/j.actbio.2015.03.007].
The adhesive properties of microstructured ‘setae’ on geckos’ feet have generated interest among scientists hoping to learn from nature in the design of new materials. Now the micro- and nanostructures of the skin of the box-patterned gecko (Lucasium steindachneri) could also inspire new multifunctional materials, say Gregory S. Watson and Jolanta A. Watson of the University of the Sunshine Coast.
Scanning electron microscopy carried out by the team reveals that gecko skin is made up of dome-shaped scales several hundred microns in size arranged in a hexagonal pattern. Each scale comprises two layers of hairs or ‘spinules’ ranging in length from several hundred nanometers to several microns with sub-micron spacing. In between the scales, the skin consists of a single layer of similar length spinules. This micro/nanostructure creates a surface with very low adhesion for potentially contaminating particles like pollen, fungal spores, sand or dirt. The surface topography also makes the skin superhydrophobic and anti-wetting, which means that it is also self-cleaning. When water hits the skin – either rain or mist – the microstructured surface creates droplets that collect particles as they roll off.
Gecko skin also has an antibacterial effect on Gram-negative bacteria, while remaining compatible with human eukaryotic cells. The researchers think that the nanoscale spine-like structures in gecko skin have a killing effect on soft-walled bacteria, which are often the most pathogenic.
“The rise of materials with intrinsic physical-based antibacterial effects is very timely and has enormous significance and benefits for biomedicine and healthcare,” explains co-author David W. Green of the University of Hong Kong.
In more general terms, the multifunctional features of gecko skin offer a model for artificial materials where contact with liquids, solids, or biological agents needs to be controlled.
“Gecko skin represents a template for functionality incorporated into a thin, wear resistant, highly flexible/deformable sheet,” says Gregory Watson. “This unique template could provide the basis for surface designs for numerous applications or materials [such as] medical and dental implants and other medical equipment, self-cleaning indoor and outdoor surfaces, marine structures, and membranes.”
But, says Jolanta Watson, the main driver for the studies was basic curiosity. “Without asking the simple question of ‘why does this happen?’, many of our modern technologies would never have been invented.”