Cuspation Present and Future Applications

Abstract

Form creates function: an axe or a lens works by shape. But there exists a group of products called structured materials which derive function not from overall shape but from a repetitive fine structure. Structured materials are diverse in form and use – there are perhaps twenty basic types – but all are made up from numerous openwork subunits, or modules. These interact to generate complex and valuable physical properties. Every kind of module is geometrically primitive. For example, in knitted fabric, the module is one loop inside another; in foamed plastic, the module is a bubble in resin or rubber; in corrugated cardboard, it is a wrinkle in the centre-ply. Modules are simple because it is not easy to devise apparatus for mass-producing them. A strategy for manufacture, which we shall call a method, is hard to find; hence, new structured materials are developed rarely. In the concept described here the module is a cusp, the tent-like stretch-form which occurs when we thrust a projection into an elastic sheet: a finger pushed into stockinet, for example. After early uncertainty of application, the cuspation process has been embodied in productive machinery and has two established markets. Because of its great generality the process may hold potential in structuring other media such as glass, metals and foods. The problems and potential rewards of research and development in structured materials are discussed as a worthwhile area for innovation.