Geckos are famous for their ability to walk up walls and scamper across ceilings. The dry-adhesive surface of geckos’ toes has inspired many attempts to copy this ability in an artificial material. Isabel Rodríguez at the A*STAR Institute of Materials Research and Engineering and co-workers at Nanyang Technological University in Singapore1 have now made one of the closest mimics to gecko toes yet, and shown that it has the properties to match.
Artificial hairs just a few hundred nanometers in diameter mimic the adhesive surface of a gecko’s toe-pads. Copyright : Agency for Science, Technology and Research
The geckos’ ability to cling to surfaces is not due to glue but to the millions of microscopic hairs that coat the surface of their toes. Each hair has a branched, hierarchical structure—toward its tip, each fiber breaks into multiple sub-fibers, which in turn break into hundreds of fibrils 100–200 nanometers in diameter. This structure ensures a high surface area, which helps the gecko to cling to the wall. In addition, the hairs become more flexible as they become thinner, which helps to maximize the number of fibrils in contact with the wall.
Rodríguez and her co-workers have successfully mimicked this hierarchical structure through the use of an anodization technique that allows branched nanopores to be etched controllably into sheets of aluminium foil—a process they used to form templates with which to create the dry adhesive surface. These templates were stamped into sheets of polycarbonate plastic using a process known as capillary force-assisted nanoimprinting, forming a hairy polycarbonate surface.
To evaluate the qualities of the hierarchical hair structure, the researchers created two separate surfaces: one with simple, unbranched hairs; and one in which the hairs branched at their tips to form nanoscopic fibrils (pictured) closely resembling those found on gecko toe-pads. They found that the sheer adhesion force of the branched material was 150% greater than that of the linear material.
“One of the most important findings from the study is the insight of how the fibrils can be made using a simple process,” says Rodríguez. “There have been reports of other hierarchical structures fabricated in polymers, but the fabrication methods they use are rather costly and complicated and not suitable for large scale.” The relatively high cost of previous attempts is due to the way the template is made—a problem that the team have now overcome using their porous alumina template technology. “Our branched, porous template fabrication is straightforward and allows large areas of gecko-like structures to be fabricated at low cost,” she adds.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering
InLight study: insights into chemical processes using light
05.12.2016 | Fraunhofer-Institut für Lasertechnik ILT
Physics, photosynthesis and solar cells
01.12.2016 | University of California - Riverside
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
05.12.2016 | Power and Electrical Engineering
05.12.2016 | Materials Sciences
05.12.2016 | Power and Electrical Engineering