In this chapter you will be introduced to the principles of the structure and characteristics of materials in general, and the specific features of the main classes of practical materials. These are metals and alloys, the different forms of polymer-based materials, ceramics and glasses, composite materials and natural materials. This is followed by discussions on how these structures give rise to the specific properties of these material classes, with an emphasis on the mechanical and physical properties and the chemical stability of materials in various environments, especially the physiological environment. Attention is given to many different specialized materials that are now used in health care, including nanocomposites, quantum dots, polymeric micelles, dendrimers, hydrogels and biopolymers. The objective is to allow you to understand why these different materials have their own properties and how biomaterials can be designed to meet the very critical performance specifications required in medical technology.

Introduction

It is important to start reading this chapter with no preconceived ideas of what a material should look like or how it should perform. In order to understand and appreciate the high-performance, esoteric materials that are used in advanced engineering applications of the twenty-first century, including medical engineering, it does not help to have fixed in our minds the idea that a material has to look and behave as if it were a macroscopic, solid object that is made by some conventional manufacturing process and which we can hold in our hand and examine visually. Most of today’s sophisticated materials do not behave in a similar manner to the more traditional steel, plastic, textile, glass, concrete or wooden structures that have been the mainstay of materials engineering for many decades. We should not be constrained by concepts of state (materials do not have to be solid), of size (they may be macroscopic, microscopic or of nanoscale dimensions), of activity (they do not have to be inert but may be intentionally active, or even living) or of permanence (they may be intentionally biodegradable). They do not have to be manufactured by conventional means but may be formed in situ by self-assembly. In other words, a collection of intensively active, macromolecular self-assembled nanoparticles is just as much a material as the piece of forged titanium that constitutes the bulk of a total hip replacement prosthesis.