Gecko tape
Encyclopedia
Gecko tape is a new material
still at the development stage. Directional adhesion refers to the ability of an adhesive
material to grip a load in one direction and to release its grip when the direction is reversed.
, is so called because it is based on the ability of the gecko
to adhere to surfaces — regardless of a surface's orientation — due to millions of microscopic hairs, called setae, on the gecko's toes. Due to the principles of electrostatics
, the setae of the gecko have a non-zero electrical charge which, when close to a surface, causes the setae and surface to attract.
Although an object normally has an average electrostatic charge of zero, at the microscopic scale of the setae, the charge varies. For example, one side of an individual seta has a slight positive charge while the other has a corresponding negative charge. Furthermore, the point of interaction on the surface also has a slight charge. Where a seta contacts the surface, there is a charge difference leading to an attractive force between the two (the van der Waals force
). This force, occurring on a tiny scale between two very close objects, is extremely small, but when multiplied by a large factor, becomes significant. Because the setae on a gecko's toe number in the millions, the combined force is enough that a gecko can hang from a ceiling — of any material — by one foot.
Scientists' effort to replicate the setae, commonly called gecko tape, is still in the early stages of development, but there has been good progress (notably by Andre Geim
's group).
Using a process called soft lithography, scientists have created a polymer that can stretch up to 200% in all directions. This means that the polymer could be placed directly on the heart and mimic its natural rhythm.
In robotics
, if gecko tape were fixed to the tracks of robots, they might be able to reach the tops of cliffs or mountains with relative ease. This would make scouting out a landscape easy.
Material
Material is anything made of matter, constituted of one or more substances. Wood, cement, hydrogen, air and water are all examples of materials. Sometimes the term "material" is used more narrowly to refer to substances or components with certain physical properties that are used as inputs to...
still at the development stage. Directional adhesion refers to the ability of an adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
material to grip a load in one direction and to release its grip when the direction is reversed.
Description
Gecko tape, an example of biomimicryBiomimicry
Biomimicry or biomimetics is the examination of nature, its models, systems, processes, and elements to emulate or take inspiration from in order to solve human problems. The term biomimicry and biomimetics come from the Greek words bios, meaning life, and mimesis, meaning to imitate...
, is so called because it is based on the ability of the gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
to adhere to surfaces — regardless of a surface's orientation — due to millions of microscopic hairs, called setae, on the gecko's toes. Due to the principles of electrostatics
Electrostatics
Electrostatics is the branch of physics that deals with the phenomena and properties of stationary or slow-moving electric charges....
, the setae of the gecko have a non-zero electrical charge which, when close to a surface, causes the setae and surface to attract.
Although an object normally has an average electrostatic charge of zero, at the microscopic scale of the setae, the charge varies. For example, one side of an individual seta has a slight positive charge while the other has a corresponding negative charge. Furthermore, the point of interaction on the surface also has a slight charge. Where a seta contacts the surface, there is a charge difference leading to an attractive force between the two (the van der Waals force
Van der Waals force
In physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...
). This force, occurring on a tiny scale between two very close objects, is extremely small, but when multiplied by a large factor, becomes significant. Because the setae on a gecko's toe number in the millions, the combined force is enough that a gecko can hang from a ceiling — of any material — by one foot.
Scientists' effort to replicate the setae, commonly called gecko tape, is still in the early stages of development, but there has been good progress (notably by Andre Geim
Andre Geim
Andre Konstantin Geim, FRS is a Dutch-Russian-British physicist working at the University of Manchester. Geim was awarded the 2010 Nobel Prize in Physics jointly with Konstantin Novoselov for his work on graphene...
's group).
Problems
- Self-mating. If the density of the spatulas is too great then self-mating occurs, and scientists have so far been unable to find the correct balance of seta density.
- Self-cleaning. In a gecko the hairy adhesive pads clean themselves of dust so they are reusable. Scientists have been unable to replicate this event, so they have been unable to reuse the tape.
- Surface energy. Different surfaces have different surface energies. For example, a liquid has a higher surface energy than a solid. Within solids the surface energy differs, so a table has less surface energy than Blu-TackBlu-TackBlu-Tack is a versatile, reusable putty-like pressure-sensitive adhesive produced by Bostik, commonly used to attach papers to walls or other surfaces....
. This is a problem because the correct balance is needed: if there is too little surface energy the tape sticks to nothing, but if there is too much it sticks to the dust and the dirt but not to the surface.
Uses of gecko tape
The predicted uses of gecko tape span from nanosurgery to aerospace. For example, in medicine it could be used as the doctor's "duct tape" to patch up organs and even to deliver medicine directly to the organ needed.Using a process called soft lithography, scientists have created a polymer that can stretch up to 200% in all directions. This means that the polymer could be placed directly on the heart and mimic its natural rhythm.
In robotics
Robotics
Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...
, if gecko tape were fixed to the tracks of robots, they might be able to reach the tops of cliffs or mountains with relative ease. This would make scouting out a landscape easy.