The first time I looked into a microscope, I was amazed. Earlier that day, my science teacher had waded into the creek near our elementary school and pulled up a bucket of muddy water. After he distributed samples on microscope slides to the class, I brought the image into focus and found myself staring at a tiny monster—a rotifer, sucking up helpless microbes around it—trapped in a drop of water.
That memory is not unique. Most people are probably stunned the first (or really any) time they peer through a microscope. In spite of their small size, the creatures that populate the tiny worlds that come into view are remarkably complex. They can sense, communicate, process information, and explore. What if it were possible to build a machine the size of a microorganism that engineers could communicate with and directly control? I learned early on that nature builds such organic robots all the time. The question is how to pull it off synthetically for ourselves.
Fortunately, scientists already know how to build many of the key components needed for a microscopic robot. Electronics have been shrinking for the past 50 years. And with today’s state-of-the-art fabrication technology, nearly a million transistors can fit in the space of a paramecium. The smallest computer—complete with a microprocessor, memory, a thermometer for sensing, and an LED for two-way communication—is just a few times as large as a hair’s width. In principle, those technologies could readily be adapted into the core of tiny machines that sense, think, and act.

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