Computer chips process and store much of the information the machines we rely on need to work well. These chips are inside of our cell phones, tablets, and other computers. Each one of them can contain billions of transistors. As electricity moves through these transistors, it causes them to heat up. If they get too hot, they won’t be able to work properly, which means the computers they’re in will fail. (Click on this link to learn more about transistors. And check out this video on the history of electronic computing. Transistors show up at about 7:44.)
“What’s the best way to get heat out of a confined space?” asks Mechanical Engineer Alex Fowler. He has spent years focusing on an area of physics called heat transfer, studying the different geometric shapes, materials, and processes which heat up and cool different objects, including computer chips and their transistors.
Animals’ hair keeps them warm. Did you know that it also cools them off? Each strand of hair or fur helps heat escape from an animal’s body, cooling it down. But once you add a certain amount of fur to its skin, Fowler explained to Math4Science, it begins to warm the animal’s body up. At which point does the change from cooling to warming happen? And when wind changes the shape of the fur, how does that affect its cooling and heating properties?
Learning the answers to these questions might help stop computer chips from burning out. Should manufacturers use fur-shaped pins or flat plates to cool electronic devices like computer chips? Fowler and his colleagues created computer models to figure this out. One simulated pins in air. Another modeled a fur-covered surface. Partial differential equations, mathematical calculations which Fowler says “govern everything interesting,” played a key role in these models.
Cooling computer chips and using plates or pipes to create industrial heat-type exchangers involved playing with geometry “to find optimal guiding principles for creating the very best (or very good) heat exchange surfaces.”
Fowler, who grew up in Massachusetts, “decided at a pretty early age that I wanted to solve major problems in the world.” The best way to do that, he figured, was to become a doctor or an engineer.
After Alex earned an A- in honors algebra, his math teacher discouraged him from going into honors geometry. She told him, “I know you don’t have what it takes to be successful in math.” Luckily, his mother intervened, confident that her son did in fact have what it takes. Though he majored in philosophy at Wesleyan University, Fowler took high-level math and science classes in college and beyond.
After college, Fowler worked as a medical technologist at Massachusetts General Hospital, spending time with cardiac surgeons. He also took biology and chemistry courses and decided to go into engineering, which he studied at Duke University, in North Carolina.
Eventually, Fowler collaborated with Mehmet Toner, whom he describes as “a rock star of science.” One project they worked on together was designed to help burn victims.
When skin burns, it dies. Then blood vessels gather under it to help with the healing process. But when too much of that happens, people can get “these massive, deforming scars” which can be “stiff, rigid, immobilizing, and painful.”
Fowler and Toner worked together to try to find a way to prevent those scars from forming. They used lasers to shoot photons into skin tissue, noting when the temperature rose enough to destroy blood vessels.
They also created models to show how photons (light particles) would behave in skin. Would they be absorbed? Or would they scatter? “How,” they asked, “could you deliver energy deeper into the skin without damaging it?”
Measuring the temperature of tiny things like a skin cell, a red blood cell, or some liquid near a cell, requires special instruments. Fowler points out that you can use a thermometer to measure the temperature of the water in a swimming pool. Whenever you put “two bodies in contact with each other, they go to each other’s temperature.” So “the thermometer changes the temperature of the swimming pool.” It heats the pool just “a little bit if it was warmer than the water.” But you can still get a very accurate reading of the water’s original temperature because the change “was an immeasurably small amount.”
Fowler and his colleagues measure the temperature of cells, which can be less than 10 microns in diameter. A micron is a millionth of a meter. Human hair ranges from 17 to 181 microns across just one strand. Any thermometer you build would be too large to measure the temperature of a cell: the tool would change the temperature of the cell.
Instead, Fowler used a thermocouple, which contains two types of metal. Its “two tiny 10-micron wires form a junction with a thermoelectric effect.” They create a voltage, which changes, depending on the temperature. The thermocouple “can respond quickly to give you a decent sense of how things are heating up or cooling down.”
Fowler and the scientists and engineers working with him also “did a lot of fluorescent measuring to see whether cells [were] alive or dead.” They used a dye that only penetrates cell membranes if those cells are dead. If it made it in, they would see the cells turn red. If the cells stayed green, they were alive. This was useful when Fowler experimented with cryogenic preservation, investigating whether liver and skin cells could be frozen without being killed. Of course a red dye would not show up as well when they worked with blood cells, so they used a different dye for red blood cells.
Teaching at the University of Massachusetts in Dartmouth, which he has done since 2000, provided Fowler with “one of the best things about my career .. a balance of teaching and research.” It’s important to “get your head into” your research “in a very deep way.” Fowler urges his junior colleagues to “set aside some time to concentrate on research.”
But he also makes teaching a priority. “Teaching poorly is really easy and teaching well is really, really hard.” It’s important to make sure “you set aside enough time to do a thorough job of course preparation.” Teaching and research are “two great activities, each of which can take your full attention.”
Fowler has taught thousands of students during his career. For almost all of his students, he says, the difference between success and failure is how hard the students work. Unlike his algebra teacher, who thought future math success depends on “having what it takes,” he believes that success mainly requires “doing what it takes.” “Learning to be an engineer is hard. To be really good, algebra, trigonometry, and calculus have to become as comfortable and understandable to you as reading — something you do and comprehend without even thinking. But that level of mastery is not something you’re born with. It’s something you work to achieve.” Fowler urges his students to do that. “If they want to work for it, they can be successful, and I’m here to help.”