Page 66 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 2 Materials: How to Choose and Where to Find Them 47

Foam Core
Foam core is made of stiff foam sandwiched between two stiff paper boards. It’s
lightweight, easy to cut, easy to glue, and easy to find. Your local arts-and-crafts
store, as well as just about anywhere with a stationery or school supplies section,
will carry it.

Semiconductors

Semiconductors have electrical properties halfway between electrical conductors
(metals) and insulators (ceramics). These materials have made integrated circuit chips
possible, and enabled the electronics and computers we take for granted every day.

You won’t work directly with semiconductors in this book, but you will use components
made from them (like transistors), so it helps to know what they are.

Biomaterials

A biomaterial is a nonliving material used in a component that interacts with the human
body. Biocompatibility is the ability of a material to avoid rejection by the body. 2

Some common biomaterials are titanium, stainless steel, PMMA (the pinkish translucent
plastic used in dental devices like retainers), Teflon, and silicone. For our purposes,
these will come into play only if you are designing wearable technology or something
that people will interact with for long periods. In those cases, you need to pay
attention to biocompatibility to avoid problems with skin allergies and to enhance
comfort. For example, if you’re designing a metal frame knee brace that generates
energy when you walk, realize that up to one in four women have metal contact
allergies (less than half that many men), and you should put a biocompatible pad of
neoprene (or something similar) on any part of the frame that rests on skin.