here's an old saying, popular among gun enthusiasts and civil engineers: "Any problem can be solved with a sufficient application of high explosives." There's a surprising amount of truth in that, although high explosives draw their power from chemistry, which is really just the careful arrangement of atoms to produce a desired effect. Chemistry is the science of finesse, but when you magnify finesse a billion billion times you can bring a lot of force to bear. Or a little bit of force, applied very, very precisely. It's all in how you use it.
A few months ago, I was tracing an electrical fault in my wife's car. The battery was generating 14 volts, but thanks to a poor connection somewhere, only 5 of it was actually reaching the engine. And since this was one of those newfangled cars where everything's electronic, this resulted in serious misbehavior, with physical damage probably not far behind. No, I didn't solve the problem with explosives, but with any luck you'll find the story interesting anyway. Bear with me for a minute.
To make a bad analogy, water pressure is generated by pumps, or by gravity, and in a particular bit of plumbing there's only so much pressure to be had. Voltage comes from batteries or generators, and there's only so much of it, too. And resistance in electrical wires is exactly like a clog in the pipes: it reduces the pressure, sometimes slowing a firehose into a mere trickle. If you're running an electrical appliance (like, for example, the computer you're reading this on right now), then as the voltage decreases the current—the number of electrons flowing through the pipe at any given moment—has to increase. It's kind of like sucking water through a stretchy hose that expands to increase the flow rate. Anyway, currents in electrical wires are just like water currents in a pipe or stream: They burble and babble along the way, causing friction, which causes heat. So as the voltage drops and the current rises, wires get hot. You can use this effect to toast bread, or in reverse to measure the flow of heat through a wire, but in the delicate workings of a computer chip or automobile brain, it's something you want to avoid.
I finally traced the problem to the battery itself, or, rather, to the connection between the battery's posts and the car's terminals. There was visible corrosion on both, and the terminals were warm to the touch. Hellooo, electrical resistance! So I disconnected terminals from posts, cleaned both sides with a metal brush, and reattached them. The result was certainly an improvement—six volts instead of five—but not enough to start the car or to keep its electronics from freaking out. It kept thinking I was trying to steal it, even though I had an electronic key to prove otherwise.
So I took the terminals off again and cleaned the whole thing with alcohol, then dried it off and washed it again with water, another surprisingly strong solvent. Then I reattached the terminals, and saw another small, insufficient improvement. Seven volts. Hmm. By now I was starting to get irritated, because this was a simple problem, and ought to have a simple solution.
Here's the deal, not only with my car but with all kinds of electrical and electronic gizmos: Metal isn't flat. In fact, on the atomic scale, it can be downright mountainous, as you can see in the attached scanning tunneling microscope image of a gold surface that, to the naked eye, looks mirror-smooth. In the real world, surfaces always have scratches and ridges, as well as a patchy film of dust and smog, oxidation and condensation, bacteria and pollen and whatever else happens to be floating around in the air. As a result, when you stick a metal plug into a metal receptacle, less than 10 percent of the two surfaces may be in actual physical contact. Most of the metal is separated by gaps ranging in size from a fraction of a millimeter to a fraction of a nanometer—roughly 1 million times as small, but still huge from the viewpoint of an electron trying to leap across.
Science can be a smash
Fortunately, at stores like Radio Shack you can buy a product called a contact enhancer, which consists of millions of microscopic particles of metal—usually gold—suspended in a solvent. You paint it on, wait for the solvent to evaporate, then plug in your connectors. The idea is for the gold to find its way into those gaps and act like a million tiny wires, increasing the metal-to-metal contact area and reducing the resistance of the connection by as much as 25 percent. That's a big difference, and even stronger gains can be achieved with solutions of ultrafine diamond dust, with particles under 100 nanometers (that's 0.001 millimeters) in size.
I always try keep some contact enhancer around, for stereo and computer equipment and other assorted projects, and when I coated the battery terminals with it I saw still another marginal improvement, from 7 to 8 volts. Working better, yes, but not actually working. The problem being, those gold and diamond particles were filling up large and medium-sized gaps but doing nothing for the really small ones, which are more numerous. Most people don't have a working nanotech lab in their basements, but I happen to, so my next trick was to paint those damned contacts with carbon nanotubes, reasoning that such very thin conductors—as little as one nanometer across, about the width of a DNA double helix—would complete the job that gold and powdered diamond had begun. Can you guess what happened? Once again, the voltage increased, this time to 9 volts. At this level the car seemed to work again, but it was marginal at best.
By now, any sane person would be thinking about buying a new battery, or new terminals, or new cables or, better yet, all of the above. But I'm a science-fiction writer, and an engineer, and my growing frustration was now compounded by a stronger curiosity. The car was only a few years old, and the battery was practically new. How could the connection be so crappy? The problem had to be grossly mechanical in nature—a physical bowing of the terminal or post that kept the contact area far below 10 percent. Cup your hands and then try pressing them together, and you'll see what I mean. But car battery terminals are made of lead—a soft metal—so I did what scientists and craftsmen have been doing to metal for thousands of years: I hit it with a hammer.
And as luck would have it—or, rather, as the laws of physics would have it—this approach was a lot more successful than anything I'd already tried. After three stout whacks on each battery post, those terminals were snug, and the car's measured voltage was indistinguishable from the battery's own. For practical purposes, I had 100 percent contact.
Nanotechnology isn't golden
There's an interesting lesson buried in this story, because however cool and wonderful our new-millennium gadgets become, sometimes there's no substitute for brute, Newtonian force. This is not to say contact enhancer and carbon nanotubes don't have their place. They both worked, improving a near-zero connection to something that was almost usable, and if not for the bent terminals they'd have solved my problem all by themselves. But without that bit of ungentle knocking, they could never reach their full potential. I didn't need any sort of high-tech tool, either; I could just as easily have used a rock. Really, we've never left the Stone Age behind, and I'm guessing we never will. And armed with this dynamic duo—nanotechnology and a hammer—we may find the range of problems we can solve growing very large indeed.
Think of a bone. It's living tissue made up of trillions of cunning microstructures, held together by the strength of chemical bonds. When a bone breaks, mechanical energy is focused to a fine point, breaking these bonds, separating one object into two. But bones are also full of stem cells—nature's own nanomedical robots—which rush to the site of the fracture and immediately start knitting the pieces back together. In trillions of chemical transactions—tiny explosions, if you will—they expend the energy to restore all those bonds, one by one and bit by bit, in delicate traceries too fine for human senses to perceive. Cool, right? But first you have to set the bone. You have to physically grab it, pull and straighten it, fit the jagged ends back together again under the tension of muscle and sinew. There's nothing delicate about that; it's hammer science, pure and simple. Much like breaking the bone in the first place.
Mining is another good example. A lot of science-fiction writers seem to believe that our nanotech future will bring an end to scarcity. We'll just snap our fingers, and a pile of gold will appear right in front of us, like magic. Right? Unfortunately, gold is a rare element in Earth's crust—about 0.00000003 percent by volume—which is why it's valuable in the first place. Yeah, good nanotech—which is really just another word for good chemistry—can help you extract the gold atoms from a gram of crushed rock, but even in a particularly high-grade ore, we're not talking about a large number of atoms—roughly one in a million. As a result, we have to process tons—even hundreds of tons—of material before we have enough gold to make a necklace. Nanoscientist Robert A. Freitas has calculated that even with highly efficient nanorefineries at our disposal, extracting gold from ordinary soil, rocks and seawater will always cost more in energy than it yields in valuable metal. So, nanotech or no, we'll still have to go prospecting, dig holes, blow up mountains, shift and pulverize house-sized boulders. ... Barring some unforeseen alchemical breakthrough, in 100 years—maybe even 100,000 years—the hammer science of mining will look much like it does today.
So by all means, let's head back to those college textbooks and relearn the arts of chemistry and physics, electronics and biology, but this time with an eye toward the bleeding edge of nanotech and the miracles it promises. But keep your other hand on that old claw hammer, because sooner or later, you're going to find something that needs a good bashing.
Sources used for writing this column can be found here.
Wil McCarthy is a rocket guidance engineer, robot designer, nanotechnologist, science-fiction author and occasional aquanaut. He has contributed to three interplanetary spacecraft, five communication and weather satellites, a line of landmine-clearing robots and some other "really cool stuff" he can't tell us about. His short writings have graced the pages of Analog, Asimov's, Wired, Nature and other major publications, and his book-length works include the New York Times notable Bloom, Amazon "Best of Y2K" The Collapsium and most recently Lost in Transmission. His acclaimed nonfiction book, Hacking Matter, is now available in paperback.
