Spiderman gloves

N PUGNO
2008 Nano Today  
Theoretical van der Waals gloves could generate an adhesion force comparable to the body weight of ~500 men. Even if such a strength remains practically unrealistic (and undesired, in order to achieve an easy detachment), due to the presence of contact defects, e.g. roughness and dust particles, its huge value suggests the feasibility of Spiderman gloves. The scaling-up procedure, from a spider to a man, is expected to decrease the safety factor (body weight over adhesion force) and adhesion
more » ... ength, that however could remain sufficient for supporting a man. Scientists are developing new biomimetic materials, e.g. gecko-inspired. Here we complementary face the problem of the structure rather than of the material, designing and preliminary fabricating a first prototype of Spiderman gloves, capable of supporting ~10 kilograms each on vertical walls. New Adhesive Optimization Laws are derived and applied for increasing the capability of the scaling-up. The gecko's ability to "run up and down a tree in any way", was firstly observed by Aristotle in his Historia Animalium, almost 25 centuries ago. A comparable adhesive system is found in spiders and in several insects. In general, when two solid (rough) surfaces are brought into contact with each other, physical/chemical/mechanical attraction occurs 1 . The developed force that holds the two surfaces together is known as adhesion. A simple example is suction. Suction cups operate under the principle of air evacuation, i.e., when they come into contact with a surface, air is forced out of the contact area, creating a pressure difference. The adhesive force generated is simply the pressure difference multiplied by the cup area. Thus, in our (sea level) atmosphere the achievable suction strength is coincident with the atmospheric pressure, i.e. about 0.1MPa. Such an adhesive strength is of the same order of magnitude of those observed in geckos and spiders, even if their adhesive mechanisms are different, mainly due to van der Waals attraction 2,3 and also capillarity 4 . Thus, although several insects and frogs rely on sticky fluids to adhere to surfaces, gecko and spider adhesion is fully dry. ISSN:1748 0132 Appendix: Mathematical derivation of the AOL In the segment i, of length z i , cross-sectional area A i and Young's modulus E i , the axial force N = F -X 1 -... -X i imposes an elongation N z i / (E i A i ) that must be equal (compatible) to the relative displacement between the contact points i and i+1, namely X i /k i -X i+1 /k i+1 . We accordingly find that the following equations must hold:
doi:10.1016/s1748-0132(08)70063-x fatcat:nmmrf3uslvhhjpexqkh7om3mqy