American scientists have developed a new, more simple method to create artificial analogues of the pads of a Gecko that can stick to various surfaces. They proposed to introduce into the partly frozen polymer metal plate and then pulling them back, causing the polymer forms a plate, which is responsible for strong adhesion to surfaces. Tests have shown that the generated by this method adhesive pad allow you to increase your grip 40 times through their shift relative to the surface, say the authors of an article in ACS Applied Materials & Interfaces.
Scientists and engineers often borrow successful designs or materials from nature, and one of the most famous examples of this are the feet of geckos. Their surface is covered with many hairs and flat plates. Upon contact with a relatively smooth surface, e.g. a leaf, these hairs are firmly against it, because of what is between the hairs and the surface there is a strong attraction based on the strength of van der Waals forces. The geckos total force of attraction of the legs to a smooth surface by several orders of magnitude exceeds the minimum necessary for retention, but more interesting is that they can easily lift them off the surface, controlling the angle of the hairs.
Scientists already know how to create a similar artificial devices, mainly based on arrays of thin plates, and there are even serial industrial manipulators for smooth objects that operate on this principle. But the methods used to create these adhesive surfaces based on casting the polymer into a form with lots of very fine grooves, which is necessary to produce using photolithography. Kim Jae-gang (Jae-Kang Kim) and Michael Vorenberg (Michael Varenberg) from Georgia Institute of Technology have developed a simpler method that does not require you to produce complex form for casting.
For the production of adhesive film by a new method suitable simple shape with a rectangular cross section, in which you need to fill a two-component plastic precursor, which is then after some time solidifies and becomes a polyurethane or polyvinylsiloxane (the researchers created the samples, consisting of one of these polymers to compare properties and choose the best material).
In the liquid preform from the precursor in the form of scientists inserted the array of the plurality of thermal knives. They have different thickness, 229 and 76 micrometers, and different ends of the V-shaped and U-shaped. After a certain time, an array of knives rises for a short distance. On the basis of experimental data, the researchers carefully picked up the rise time for each polymer and the configuration of the array of knives: the polymer needs to reach a sufficient viscosity to rise along with the knives, but not too big that it may rupture when lifting.