The definition of Biomaterial can be found in a Merriam-Webster’s dictionary, dated 1966: A natural or synthetic material (as a metal or polymer) that is suitable for introduction into living tissue especially as part of a medical device (as an artificial joint). However, with the advances in technology, materials that are used ex vivo, but interacting with living organisms can be arguably a biomaterial. For example, blood contacting materials such as plasticized polyvinyl chloride (PVC) commonly used in blood bags, may be considered as a type of biomaterial. More recently, rapid diagnostic tools using miniaturized fluidic channels1 combining with micro mixers, valves and pumps have the potential to fundamentally change the ways biochemical analysis have been performed. Thematerials involved in such devices or systems include silicon, glass, metals and polymers. These materials, either

used for the substrates, passive parts or active elements, need to interact with biological components such as cells, proteins, DNAs, genes or reagents. The interfacing mechanisms and reactions between the biological components and the mechanical parts are not often discussed or taught in the curricula of conventional MEMS courses in the departments of electrical or mechanical engineering. Thus, the purpose of this book is to introduce biomaterials to engineers who are interested in MEMS and microfluidics, yet have no prior background in biomaterials.