Sticky Feet: From Animals to Materials
- PDF / 492,186 Bytes
- 7 Pages / 585 x 771 pts Page_size
- 81 Downloads / 170 Views
6/12/2007
12:04 AM
Page 466
Yet many animals, including flies, beetles, rather large spiders, and gekkonid lizards, have feet covered with tiny specialized hairs that allow them to run fast on the ceiling and support a force many times their weight. The foot of a chrysomelid beetle is shown as an example in Figure 1. Tree frogs, bees, and grasshoppers can do it without hairs by using the highly specialized material structure of their adhesive feet, which enables them to match perfectly the surface profile of the substrate.17–21 The question is: Can we learn from these animals how to develop new materials able to reversibly stick to a variety of surfaces?
Sticky Feet: From
Animals to Materials Costantino Creton and Stanislav Gorb, Guest Editors
Abstract Many insects and some larger animals, such as geckos, skinks, and tree frogs, can easily climb vertical walls and even walk on the ceiling. These abilities require a method to attach the feet strongly but reversibly to a variety of surfaces—smooth or rough, hydrophilic or hydrophobic, clean or containing contaminants. This issue of MRS Bulletin examines how fibrils, absorbed water layers, geometry, and other factors make reversible adhesion possible, and how this understanding might be applied to robots and other artificially created structures that can climb walls, walk on ceilings, and get to other hard-to-reach places.
Overview: Reversible Adhesion in Locomotion During the last decade, a diverse community of biologists, physicists, solid mechanics specialists, and, at the end of the chain, engineers designing robots have been busy studying the complex features of reversible adhesion in biological systems1–7 and investigating which concepts could act as inspiration for the development of artificial reversible adhesive systems.8–10 We felt that the field, although relatively new, was mature enough to be presented to a materials science audience for its creative concepts, some of which can be readily extrapolated to the field of materials adhesion. The key concept behind this work is the understanding of locomotion in nature. Many insects11,12 and some larger animals, including tree frogs and lizard species such as geckos and skinks, can easily climb vertical walls and even walk on the ceiling.6,13–15 This ability requires a method for attaching the feet strongly but reversibly to a variety of surfaces—smooth or rough, hydrophilic or hydrophobic, clean or containing contaminants. This feat is hardly possible with conventional adhesives. Pressure-sensitive adhesives (PSAs) can stick to most surfaces by simple contact and slight pressure,16 but once they are detached, reattachment is usually difficult because of contamination issues. Furthermore, the detachment force cannot be tuned as a function of time. If the adhesive sticks, it will keep sticking:
466
“Sticky Feet”: Morphology and Mechanisms
imagine yourself walking on the ceiling with double-sided tape on your feet. Force that you apply to the tape on one foot will generate substrate resistance, which wi
Data Loading...
