Ultraviolet controlled super-adhesive coating
A small group of scientists from Kiel University, Germany, has developed a new super-adhesive technology that uses principles embodied by nature in the form of the surface of gecko limbs. We have already talked more than once about successful and not very successful attempts to repeat these principles, but almost all developed technologies used heat or specialized electronics to control the adhesive properties of the material. The principle of controlling the properties of the material, developed by German scientists, is much simpler: to change the “stickiness” you just need to illuminate it with ultraviolet light with the appropriate parameters.
The new material has a structure made up of three different layers. Its top layer is a surface covered with microscopic structures that resemble a mushroom with a flat hat. It is this layer that comes into contact with the surface of the material to which it adheres, and high adhesion forces arise at the numerous points of contact of the mushroom caps with the surface of another material. The bases of the mushroom legs sit on a layer of a polymer called polydimethylsiloxane, which in turn is bonded to a layer of azobenzene liquid crystals. And the last layer is also a layer of polydimethylsiloxane, which protects the liquid crystals from environmental influences.
Azobenzene crystals are sensitive to ultraviolet light; under its influence, they change their orientation and position relative to each other. In the absence of ultraviolet light, the top layer adheres and attaches securely to the surface of another material using van der Waals forces. But as soon as this “patch” is illuminated with ultraviolet light, azobenzene crystals begin to move and tear off the “mushroom caps” from the surface, which several times reduces the “sticking” force. Changing the intensity of ultraviolet light allows you to adjust the degree of adhesion, and with relatively strong light, the patch is detached from the surface quite easily.
Scientists have tested the new material’s adhesion properties on objects made from a variety of materials, including glass and plastic. The force of adhesion of the patch to the surface is large enough for a piece of material of a relatively small area to be able to support the weight of a person.
In addition to the main advantage that there is no need to use complex methods of controlling its adhesion properties, the new material has another positive quality – it absolutely does not leave any marks on the surface to which it was previously adhered. This, in turn, will make it possible to use the new material not only as an ordinary “Velcro”, but also in “clean rooms” of industrial production, in medicine and in other areas where cleanliness and sterility are required.
Source: http: // www. dailytechinfo.org