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26. Read the text and answer the questions below it.
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26. Read the text and answer the questions below it.
Short Circuits
We all know that technological progress is not an actual magic show. Still, it almost seems like magic the way the transistor, the main component in all modern electronics, has diminished in size since being invented in 1947. The first transistor, made of gold, plastic, and germanium, was about the size of an adult’s fingernail. Today’s transistors, etched on silicon wafers, can’t be seen with the naked eye. The minimum size of a transistor is now 45 nanometers. A nanometer is one-billionth of a meter - roughly the width of three or four atoms. Computer engineers are trying to make transistors even smaller. How tiny can they go?
Chip Switches
Every transistor has the same basic properties: It can both conduct and stop the flow of electricity. The word transistor is a combination of two words: transfer and resistor. All transistors are made from materials called semiconductors. A semiconductor is a cross between a good conductor (such as copper) and a good insulator (such as rubber). It can be made to accept or reject the flow of electrons in a circuit. Germanium, used in the first transistors, is a semiconductor. So is silicon, widely used today. A transistor’s ability to control the flow of electricity has made possible our entire computerized world. All computers depend on the binary system to convert electric signals into useful information. The binary system has only two numbers: 1 and 0. When a transistor allows electricity to flow through, it registers a 1. When the transistor stops the flow of electrons, it registers a 0. Millions or billions of those 1s and 0s, flashing off and on hundreds of millions of times a second in programmed patterns, enable your computer to do everything it does — from allowing you to play World of Warcraft to letting you type up a school science report.
Inner Limits
A transistor that is only a few atoms wide is incredibly small. But researchers want to make transistors even smaller and cheaper to produce. Chip-making technology has run into a big problem, however. Transistors smaller than 45 nanometers and etched on silicon chips don’t work very well. They tend to leak electrons, making them less efficient. To get around that problem, scientists are using nanotechnology to look at new materials and new methods to produce transistors. Nanotechnology is the engineering of materials on the atomic level, building new materials from the bottom up by manipulating atoms and molecules.
One promising area of nanotechnology is the use of graphene, a carbon fabric that is only one carbon atom thick. Graphene is strong, stable, and can act as a semiconductor. If researchers can find a practical way to etch transistors onto graphene, smaller and immensely faster computer chips can be more cheaply made. “[The ultimate goal] of electronic engineers is the so-called ballistic transistor, ” physicist Andre Geim, a graphene researcher at the University of Manchester, told Live Science. “It would be very, very fast, ultimately fast, in fact. ” Another promising area of nanotechnology research involves using strands of deoxyribonucleic acid (DNA) to build transistors. DNA is the genetic material that determines the makeup of all living cells. Researchers can now take strands of DNA from bacteria and manipulate them into almost any shape they want. California Institute of Technology researcher Paul Rothemund has helped pioneer that technique. He has twisted DNA strands into smiley faces and maps of North and South America.
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Rothemund and others are looking to shape DNA strands into a kind of scaffolding that could be attached to silicon wafers to make transistors. Because DNA does not conduct electricity, scientists are experimenting with ways to combine DNA with atoms of conducting materials, such as gold, to build transistors. DNA replicates (copies) itself. So, if researchers can produce a DNA transistor, all they have to do is add the right “soup” of chemicals, and the DNA would reproduce itself, making millions of new nano-sized transistors at little or no cost.
Smart Dust
Making transistors much smaller and much more cheaply could transform our lives. Tiny, smart nanomachines could do any number of things quickly and invisibly. Their greatest use might be in medicine. Swallowed in a pill or injected, tiny, computerized “nanobots” might be able to repair damaged cells one at a time, restoring health invisibly and painlessly before destroying themselves. The nanobots might repair pipes, bridges, airplane engines, and electrical equipment too. They might even help with housework. Kris Pister, a University of California physicist, envisions what he calls smart dust — nanobots that move around the house at night, eating dirt and generally cleaning up. Such things are possible in your lifetime — all because scientists are now “thinking small. ”
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