For more in-depth details on these metallic self-propelling rods, check out earlier articles on this blog here and here.
September 11, 2016
Video on Self-Propelling Platinum/Gold Rods
Here's my entry for The Art of Talking Science, an event being put on by Massachusetts General Hospital as part of the upcoming HUBweek festival. The idea is to summarize your research in 1 minute or so. They will select 8 people, who will each give a 4-minute talk on their research to a panel of judges. I'll post the results here when I know.
For more in-depth details on these metallic self-propelling rods, check out earlier articles on this blog here and here.
For more in-depth details on these metallic self-propelling rods, check out earlier articles on this blog here and here.
July 24, 2016
Swimming Particles - Future Drug Delivery Vehicles?
For my Ph.D. dissertation, I studied tiny metallic rods that propel themselves ("swim") through hydrogen peroxide. You can read more about them in my previous post here. When I tell people about these rods, the most common question I get is, "that's neat and all, but what can you use them for?" It's a fair question.
My work was mostly focused on figuring out how the rods swim in the first place, which was fun in itself. But there's some rather tasty icing on the cake: in addition to being interesting, it turns out that "nanomotors," the general term for microscopic swimmers such as the platinum-gold rods, may indeed have some important useful applications.
Above, we see that the rods can "tow" a piece of "cargo" (e.g. a tiny polystyrene sphere) from one pre-defined point to another (for more, see this previous post). Today we'll discuss one of the possibilities this raises, related to improving cancer treatment.
A Brief Introduction to Chemotherapy
Chemotherapy (or "chemo") generally refers to the use of drugs to treat cancer. Most chemo drugs are administered intravenously, entering the patient's bloodstream and attacking cells all over the body (including, but not limited to, the cancer cells - see note 1). Thus, even when successful, chemotherapy often kills healthy cells, causing many of the serious side effects of chemo that you're probably familiar with (and may have experienced yourself). It's kind of like setting off an atomic bomb inside the body; it destroys more than just the intended target.
Can we do better?
Targeted chemotherapy
There's a new type of cancer treatment known as targeted cancer therapy. The idea is to make "smarter" drugs that target the attributes of cancer cells that make them cancerous in the first place. As their name suggests, targeted cancer drugs need to be delivered to a specific location: directly to the tumor, rather than the whole body. But drugs can't find cancer cells on their own. To make targeted chemotherapy work, you typically need something to carry a drug directly to a cancer cell to kill it, but not harm the surrounding healthy cells in any way. Instead of an atomic bomb, these drugs act like a sniper, only targeting the bad guys.
But how do you get the drug to the cancer cell?
Could Nanomotors Deliver Drugs?
Enter Professor Joseph Wang, at the University of California, San Diego, and his research team (a one-time collaborator of ours). They recently developed a different kind of swimmer from the ones I studied: they manufactured tiny, cylindrical tubes made of a bio-compatible (i.e., non-toxic) material coated with zinc. They're about 20 micrometers long, about 1/5th as long as a human hair is wide. Most importantly, these swimmers are powered not by peroxide (which is toxic to humans), but by acid: the zinc reacts with the hydrogen ions in the acid and turns them into hydrogen gas bubbles. The bubbles are ejected from the tube, which acts kind of like a rocket: the recoil from the bubble release propels the swimmer forward, as illustrated below.
So, why would an acid-propelled swimmer be useful? Isn't acid harmful?
My work was mostly focused on figuring out how the rods swim in the first place, which was fun in itself. But there's some rather tasty icing on the cake: in addition to being interesting, it turns out that "nanomotors," the general term for microscopic swimmers such as the platinum-gold rods, may indeed have some important useful applications.
 |
| A rod-shaped "nanomotor" swims toward a piece of inert cargo (green), tugs it along for a short period (red), and releases it at a predetermined location before swimming away (green). |
A Brief Introduction to Chemotherapy
Chemotherapy (or "chemo") generally refers to the use of drugs to treat cancer. Most chemo drugs are administered intravenously, entering the patient's bloodstream and attacking cells all over the body (including, but not limited to, the cancer cells - see note 1). Thus, even when successful, chemotherapy often kills healthy cells, causing many of the serious side effects of chemo that you're probably familiar with (and may have experienced yourself). It's kind of like setting off an atomic bomb inside the body; it destroys more than just the intended target.
Can we do better?
Targeted chemotherapy
There's a new type of cancer treatment known as targeted cancer therapy. The idea is to make "smarter" drugs that target the attributes of cancer cells that make them cancerous in the first place. As their name suggests, targeted cancer drugs need to be delivered to a specific location: directly to the tumor, rather than the whole body. But drugs can't find cancer cells on their own. To make targeted chemotherapy work, you typically need something to carry a drug directly to a cancer cell to kill it, but not harm the surrounding healthy cells in any way. Instead of an atomic bomb, these drugs act like a sniper, only targeting the bad guys.
But how do you get the drug to the cancer cell?
Could Nanomotors Deliver Drugs?
Enter Professor Joseph Wang, at the University of California, San Diego, and his research team (a one-time collaborator of ours). They recently developed a different kind of swimmer from the ones I studied: they manufactured tiny, cylindrical tubes made of a bio-compatible (i.e., non-toxic) material coated with zinc. They're about 20 micrometers long, about 1/5th as long as a human hair is wide. Most importantly, these swimmers are powered not by peroxide (which is toxic to humans), but by acid: the zinc reacts with the hydrogen ions in the acid and turns them into hydrogen gas bubbles. The bubbles are ejected from the tube, which acts kind of like a rocket: the recoil from the bubble release propels the swimmer forward, as illustrated below.
 |
| Schematic of zinc-powered nanomotors that use stomach acid as a fuel. The chemical equation illustrates that solid zinc (on the motor surface) reacts with protons in the acid (H+), creating hydrogen bubbles (H2) which propel the swimmer forward. Meanwhile, the zinc dissolves harmlessly into the acid (forming zinc ions, with a 2+ charge). |
Well, the stomachs of many mammals, including ours, are highly acidic. Acid, as you may recall, contains plentiful amounts of hydrogen ions, which are basically protons floating around in the solution. So our stomachs are full of nanomotor fuel.
Professor Wang's research team built these swimmers and coated them with gold nanoparticles (tiny spheres of gold much smaller than the swimmers), which serve as a model "drug." They administered the gold-laden nanomotors orally to live mice. After 2 hours, the mice were, as we researchers politely put it, "sacrificed" (for science!) and their stomachs were examined. Compared to mice that had received an oral dose of nanoparticles alone, the mice that received the nanoparticle-laden swimmers showed over three times as much retention of the gold in their stomach lining.
In other words, the nanomotors acted like delivery trucks, delivering the gold "drugs" into the mice's stomach linings!
The useful thing about these swimmers is that, like the platinum/gold rods I studied, they can carry payloads. However, unlike the platinum-gold rods, they don't need hydrogen peroxide to move. They just move based on the stomach acid that's already present! Even better, the motors slowly dissolve in the stomach acid, leaving nothing toxic behind!
This is a step forward for the field of man-made micro-swimmers. There are certainly still roadblocks to overcome, of course: for one thing, we need to show that this is viable in humans, and not just for delivering drugs into the stomach lining. Remember, for targeted cancer treatment, we need to be able to guide these swimmers to a specific location - the swimmers here indiscriminately swam until they collided with the stomach lining. We do have ways of guiding self-propelling particles, but guiding them to a tumor is still a ways away.
Still, this work shows that the idea of using nanomotors to deliver drugs is not simply a pie-in-the-sky idea, as some people believe.
NOTES!
1. If you're wondering, traditional chemotherapy drugs typically target cells that divide quickly. Cancer cells divide quickly, which is why chemo drugs often work against them. The problem is that there are many other cells in the body that also divide quickly but are completely healthy. These cells are vulnerable to the chemo drugs.
Professor Wang's research team built these swimmers and coated them with gold nanoparticles (tiny spheres of gold much smaller than the swimmers), which serve as a model "drug." They administered the gold-laden nanomotors orally to live mice. After 2 hours, the mice were, as we researchers politely put it, "sacrificed" (for science!) and their stomachs were examined. Compared to mice that had received an oral dose of nanoparticles alone, the mice that received the nanoparticle-laden swimmers showed over three times as much retention of the gold in their stomach lining.
In other words, the nanomotors acted like delivery trucks, delivering the gold "drugs" into the mice's stomach linings!
The useful thing about these swimmers is that, like the platinum/gold rods I studied, they can carry payloads. However, unlike the platinum-gold rods, they don't need hydrogen peroxide to move. They just move based on the stomach acid that's already present! Even better, the motors slowly dissolve in the stomach acid, leaving nothing toxic behind!
This is a step forward for the field of man-made micro-swimmers. There are certainly still roadblocks to overcome, of course: for one thing, we need to show that this is viable in humans, and not just for delivering drugs into the stomach lining. Remember, for targeted cancer treatment, we need to be able to guide these swimmers to a specific location - the swimmers here indiscriminately swam until they collided with the stomach lining. We do have ways of guiding self-propelling particles, but guiding them to a tumor is still a ways away.
Still, this work shows that the idea of using nanomotors to deliver drugs is not simply a pie-in-the-sky idea, as some people believe.
NOTES!
1. If you're wondering, traditional chemotherapy drugs typically target cells that divide quickly. Cancer cells divide quickly, which is why chemo drugs often work against them. The problem is that there are many other cells in the body that also divide quickly but are completely healthy. These cells are vulnerable to the chemo drugs.
February 20, 2016
Dimensions and Units and Atomic Bombs, Oh My!
Dimensional analysis is the art and science of doing algebra with units. When I say units, I mean feet, pounds, meters, kilograms, femtoseconds, milliliters, etc. And there is definitely an art to dimensional analysis: despite its humdrum-sounding name, dimensional analysis is a subtle and sometimes beautiful subject that requires creative thinking to do well. When done effectively, dimensional analysis can give profound insight into the inner workings of a physical phenomenon at a fraction of the effort that one normally expends by doing many tedious experiments or calculations. It's used all the time in science and engineering.
What's the difference between dimensions and units?
Consider velocity. Velocity, of course, is expressed as a distance divided by a time. It can be measured in miles per hour, for example. In somewhat-technical language, scientists say that velocity has "fundamental dimensions of length divided by time." Notice I didn't say "dimensions of miles per hour" or "dimensions of meters per second." That's because dimensions aren't units. Units (like kilograms, meters, seconds) are arbitrary constructs of the human mind - what we call a kilogram is based on the mass of an arbitrarily sized piece of platinum/iridium alloy - while dimensions (like mass, length, or time) have a physical meaning. This turns out to be a very important distinction.
Dimensional Consistency
The key to dimensional analysis is that any physically meaningful equation has to be dimensionally consistent. For example, if I wrote an equation for the distance traveled by an object moving at a constant speed, it might look like this:
Both sides of this equation have dimensions of length. Obviously, "distance" has dimensions of length, and on the right side we have (length / time) x (time), so the "time"s cancel out, leaving length. This is what I mean by doing algebra with units. And if I were to add any additional terms to this equation, they'd better also have dimensions of length. For example, I could write
The point of dimensional consistency is that every additive term must have the same dimensions. If I tried to add another term that had dimensions of time / length, then we would know that there is something fundamentally wrong with the equation; we would lose all confidence in its ability to describe reality. This turns out to be true even in more complicated situations where the formulas are not so simple.
Dimensionless Numbers
If you were to ask me how fast a 747 airplane can fly, and I replied "987," that answer wouldn't mean very much. The obvious question is: what units am I using? I could be expressing my answer in miles per hour, meters per second, micrometers per nanosecond, or any other combination. Again, units are arbitrary.
But if you asked me "what is the Mach number of a Boeing 747?" and I replied "0.85," I've still just given you a number, but now that number has physical meaning. I've just told you that a 747 can fly at 85% the speed of sound. But, of course, it doesn't matter whether I calculated both speeds in meters per second or miles per hour - the result I get for the Mach number is independent of the untis system I use, which is precisely why the number is physically meaningful - the only reference point is something physical (the speed of sound).
The Mach number is perhaps the most familiar example of a dimensionless number. These are numbers that have no dimensions, and thus no units. It's easy to see this with the Mach number - we are dividing one speed (the speed of the airplane) by another speed (the speed of sound), so as long as we use the same units for both speeds, we will get the same Mach number no matter what unit system we choose. This turns out to have important consequences. An important result in dimensional analysis, known as the Buckingham Pi Theorem, describes how I can take a physically meaningful equation (like the one for distance above), and express it in dimensionless form. For the case of the distance equation, the dimensionless result is very, very simple:
Both sides of this equation are dimensionless. On the left I have a distance divided by (length x time), so a distance divided by a distance. On the right I just have a number. This example is pretty trivial, but it illustrates the point. Both sides of the equation are now dimensionless. OK, you say, that's great. When is this actually useful?
On July 16, 1945, about one month before the bombings of Hiroshima and Nagasaki, the United States Government conducted the Trinity nuclear test, which was the first detonation of a nuclear weapon in history. A photographer captured the explosion on camera:
The U.S. Government published 25 of these photos, each at different times, in Life Magazine in 1947. One of the most sensitive pieces of information was the yield of the bomb, or how much energy it released. Much to the government's chagrin, however, it turns out that we can use dimensional analysis to determine how the growth of the explosion is related to the yield of the bomb!
The Buckingham Pi theorem is essentially a recipe for arranging the relevant parameters into dimensionless form. I'll skip the mathematical details (some examples can be found on Wikipedia), but it turns out that the parameters that matter the most here are the yield of the bomb, which we'll call E, the radius R of the fireball, and time t, since the radius obviously grows with time. It also turns out to depend on the density of the atmosphere, which we'll call d. (see note 1). If we arrange these parameters into a dimensionless equation, we will get
What's the difference between dimensions and units?
Consider velocity. Velocity, of course, is expressed as a distance divided by a time. It can be measured in miles per hour, for example. In somewhat-technical language, scientists say that velocity has "fundamental dimensions of length divided by time." Notice I didn't say "dimensions of miles per hour" or "dimensions of meters per second." That's because dimensions aren't units. Units (like kilograms, meters, seconds) are arbitrary constructs of the human mind - what we call a kilogram is based on the mass of an arbitrarily sized piece of platinum/iridium alloy - while dimensions (like mass, length, or time) have a physical meaning. This turns out to be a very important distinction.
Dimensional Consistency
The key to dimensional analysis is that any physically meaningful equation has to be dimensionally consistent. For example, if I wrote an equation for the distance traveled by an object moving at a constant speed, it might look like this:
distance = velocity x time
Both sides of this equation have dimensions of length. Obviously, "distance" has dimensions of length, and on the right side we have (length / time) x (time), so the "time"s cancel out, leaving length. This is what I mean by doing algebra with units. And if I were to add any additional terms to this equation, they'd better also have dimensions of length. For example, I could write
total distance = initial distance + velocity x time
The point of dimensional consistency is that every additive term must have the same dimensions. If I tried to add another term that had dimensions of time / length, then we would know that there is something fundamentally wrong with the equation; we would lose all confidence in its ability to describe reality. This turns out to be true even in more complicated situations where the formulas are not so simple.
Dimensionless Numbers
If you were to ask me how fast a 747 airplane can fly, and I replied "987," that answer wouldn't mean very much. The obvious question is: what units am I using? I could be expressing my answer in miles per hour, meters per second, micrometers per nanosecond, or any other combination. Again, units are arbitrary.
But if you asked me "what is the Mach number of a Boeing 747?" and I replied "0.85," I've still just given you a number, but now that number has physical meaning. I've just told you that a 747 can fly at 85% the speed of sound. But, of course, it doesn't matter whether I calculated both speeds in meters per second or miles per hour - the result I get for the Mach number is independent of the untis system I use, which is precisely why the number is physically meaningful - the only reference point is something physical (the speed of sound).
The Mach number is perhaps the most familiar example of a dimensionless number. These are numbers that have no dimensions, and thus no units. It's easy to see this with the Mach number - we are dividing one speed (the speed of the airplane) by another speed (the speed of sound), so as long as we use the same units for both speeds, we will get the same Mach number no matter what unit system we choose. This turns out to have important consequences. An important result in dimensional analysis, known as the Buckingham Pi Theorem, describes how I can take a physically meaningful equation (like the one for distance above), and express it in dimensionless form. For the case of the distance equation, the dimensionless result is very, very simple:
distance / (length x time) = 1.
On July 16, 1945, about one month before the bombings of Hiroshima and Nagasaki, the United States Government conducted the Trinity nuclear test, which was the first detonation of a nuclear weapon in history. A photographer captured the explosion on camera:
 |
| The rapidly expanding fireball from the Trinity nuclear test, 16/1000 of a second after the explosion. SOURCE: http://nuclearweaponarchive.org/Usa/Tests/Trinity.html |
The Buckingham Pi theorem is essentially a recipe for arranging the relevant parameters into dimensionless form. I'll skip the mathematical details (some examples can be found on Wikipedia), but it turns out that the parameters that matter the most here are the yield of the bomb, which we'll call E, the radius R of the fireball, and time t, since the radius obviously grows with time. It also turns out to depend on the density of the atmosphere, which we'll call d. (see note 1). If we arrange these parameters into a dimensionless equation, we will get
 |
| Formula for the radius of the fireball as a function of the yield of the bomb E, density of the surrounding atmosphere d, and time t. K is a constant which turns out to have a value of approximately 1. |
The exponents might look a little funny, but they have to be there in order to be dimensionally consistent. It turns out that, if these are the parameters that matter, then this is the ONLY way to express the radius in terms of the other parameters in a dimensionally consistent fashion!
This equation predicts that the radius grows as time to the 2/5ths power. Is it accurate? Well, the photos (rather helpfully) have a length scale and the elapsed time indicated in each image, so we can actually use the 25 images provided to put the formula provided by dimensional analysis (above) to the test:
 |
| The predictions of the formula above, compared with experiment. The line is predicted by the theory; the + signs are data from the images. |
I hope you're blown away by the agreement between theory and experiment here, because if not, I haven't conveyed clearly enough just how easily we came up with that formula. The above plot was produced by the famous fluid dynamicist Sir Geoffrey Ingram Taylor in a 1950 paper. He subsequently used the formula above, along with some insights from the mathematical equations governing the behavior of gases, to estimate the yield of the bomb to be 16,000 tons of TNT. This turns out to be in the correct range, which was given by the head of the Manhattan Project as between 15,000 and 20,000 tons! (see note 2)
Dimensional analysis isn't easy. It took real insight for us to know the physical parameters that matter in the equation above. But when dimensional analysis is done right, it is a cheap way to learn a lot in a short period of time.
NOTES!
1) One way to interpret this is that the denser the atmosphere is, the more mass the fireball needs to push out of the way in order to continue expanding.
2) Taylor's one-time student and biographer, George Batchelor (himself a preeminent fluid dynamicist), notes that Taylor was “…mildly admonished by the US Army for publishing his deductions from their photographs.” Suffice it to say, when they added the distance and time data, the government did not appreciate the power of dimensional analysis!
January 29, 2016
Why Is It So Hard To Solve The World's Energy Crisis?
I'm teaching a class at MIT this semester called "Thermal-Fluids Engineering II." The class is largely concerned with energy, and how it is generated using machines like internal combustion engines and power plants. This post will provide some background on the current state of affairs regarding energy.
Recently, former NASA astronaut and current NASA climate scientist Piers Sellers was diagnosed with stage 4 pancreatic cancer. Two weeks ago he wrote an op-ed in the New York Times where, rather than feel sorry for himself or wax sentimental about his life, he described (in broad terms) what humanity needs to do to avoid the potentially catastrophic consequences of runaway global warming, since it is now likely that he won't be around to see what happens. After describing the initial challenges associated with making effective energy and environmental policy (which are substantial), he writes (emphasis mine),
Consider a conventional gasoline-powered car like the Toyota Camry, one of the most common cars on American roads. The gas mileage on such a car is, accounting for highway and city driving, about 30 miles per gallon. Since there are 16 cups in one gallon, this means you get about 2 miles per cup, or one mile out of about this much gas:
Let's say you put that much gasoline in the tank of a Toyota Camry and drive a mile. Then, the car breaks down, and the nearest service station is a mile away. Now imagine the amount of energy you would have to expend to push the car (which typically weighs about 3,240 pounds) for the entire mile to get there. There's a LOT of energy in that half-cup of gasoline (which, at today's prices, would currently set you back a whopping 5 cents)!
As it turns out, gasoline has a very high energy density compared with many other substances. Here's a comparison with a few other notable substances (SEE NOTE 2).
But that won't stop us from trying. In future posts, I will address the steps we are taking at MIT to try to come up with new ways to generate clean energy, and just as crucially, how to store and distribute it.
NOTES!
1. Some of you may be surprised that that much gasoline is actually required. (I was.) But the thing to keep in mind is that cars are actually quite inefficient when it comes to extracting energy from gasoline: for a typical auto engine, the average efficiency (amount of useful mechanical energy actually extracted divided by the total extractable amount) is around 18-20%. In fact, thermodynamics shows us that the best we can ever hope for with this kind of engine is around 37%. So, the "large" amount of gasoline required to drive one mile is not due to a limited amount of energy in gasoline, but due to the limitations on our capability to extract useful energy from it.
2. Source: Muller, R.A., Energy for Future Presidents. New York: W.W. Norton, 2012.
Recently, former NASA astronaut and current NASA climate scientist Piers Sellers was diagnosed with stage 4 pancreatic cancer. Two weeks ago he wrote an op-ed in the New York Times where, rather than feel sorry for himself or wax sentimental about his life, he described (in broad terms) what humanity needs to do to avoid the potentially catastrophic consequences of runaway global warming, since it is now likely that he won't be around to see what happens. After describing the initial challenges associated with making effective energy and environmental policy (which are substantial), he writes (emphasis mine),
Ultimately, though, it will be up to the engineers and industrialists of the world to save us. They must come up with the new technologies and the means of implementing them. The technical and organizational challenges of solving the problems of clean energy generation, storage and distribution are enormous, and they must be solved within a few decades with minimum disruption to the global economy.Here we'll address the question that is probably on many people's minds: why are the technical challenges associated with generating cleaner energy so enormous? Let's start by looking at the current ways in which we extract energy.
Consider a conventional gasoline-powered car like the Toyota Camry, one of the most common cars on American roads. The gas mileage on such a car is, accounting for highway and city driving, about 30 miles per gallon. Since there are 16 cups in one gallon, this means you get about 2 miles per cup, or one mile out of about this much gas:
 |
| Pictured: a one-mile drive in a Toyota Camry...from an engineer's perspective at least. (SEE NOTE 1) |
As it turns out, gasoline has a very high energy density compared with many other substances. Here's a comparison with a few other notable substances (SEE NOTE 2).
Food calories per pound
|
Compared to TNT
|
|
TNT
|
295
|
1
|
Chocolate chip cookies
|
2,269
|
7.7
|
Coal
|
2,723
|
9.2
|
Butter
|
3,176
|
11
|
Gasoline
|
4,538
|
15
|
Natural gas
|
5,899
|
20
|
Uranium-235
|
9,000,000,000
|
32,000,000
|
(Yes, 1 pound of chocolate chip cookies has the energy of 7.7 pounds of TNT!)
Now let's compare gasoline with other sources from which we draw energy, like a AA battery. How much energy is stored in it?
Batteries deliver energy in the form of electricity, which at the most basic level means moving electrons. Batteries are typically characterized by the amount of current (essentially, number of electrons per second) they can deliver, and the voltage (essentially, the amount of energy each electron carries) at which they can deliver it. Different applications require different amounts of each. A typical alkaline AA battery can deliver around 2500 milliamp-hours at 1.5 V. A milliamp is a unit of current, so in other words, it can deliver 2500 milliamps of current for 1 hour at 1.5 V. Carrying out the calculations,
Batteries deliver energy in the form of electricity, which at the most basic level means moving electrons. Batteries are typically characterized by the amount of current (essentially, number of electrons per second) they can deliver, and the voltage (essentially, the amount of energy each electron carries) at which they can deliver it. Different applications require different amounts of each. A typical alkaline AA battery can deliver around 2500 milliamp-hours at 1.5 V. A milliamp is a unit of current, so in other words, it can deliver 2500 milliamps of current for 1 hour at 1.5 V. Carrying out the calculations,
Power = Energy per Time = Current x Voltage (see this article for an explanation)
Energy = Current x Voltage x Time
Energy = 3750 Watt-hours, or 13,500 Joules.
Here I'm using the metric unit for energy, called the Joule (after James P. Joule, a pioneer in the area of thermodynamics).
So......is 13,500 Joules a lot of energy? Let's compare this to the amount of energy in food.
So......is 13,500 Joules a lot of energy? Let's compare this to the amount of energy in food.
What we call 1 food calorie is actually 1,000 "actual" calories, or 1 kilocalorie (long story - see this article), and 1 kilocalorie turns out to equal 4,184 Joules. So a AA battery contains a little over 3 calories' worth of energy. Compare that to a granola bar, which has around 200 calories in it. So, a granola bar is equivalent to 62 AA batteries in terms of energy stored!
What about the equivalent amount of gasoline? A granola bar weighs about 56 g. From the table above and some simple arithmetic, 56 g of gasoline has about 567 food calories, or the equivalent of about 186 AA batteries!
But, you say, there's plenty of energy in the Sun! We just need to harvest and store it, right?
The rate at which we receive energy (in the form of electromagnetic radiation) from the Sun turns out to be about 1000 Joules per square meter per second. On a perfect sunny day, a patch of ground with an area of 1 square meter receives about 1000 Joules every second. Sounds like a lot of energy, right? Well, setting aside the fact that this is only true in direct sunlight (and so by definition only during daytime), the issue is that most solar cells are only about 10% efficient. This means we can only extract about 100 Joules per second for every square meter of (generally expensive) solar cells that we build.
The rate at which we receive energy (in the form of electromagnetic radiation) from the Sun turns out to be about 1000 Joules per square meter per second. On a perfect sunny day, a patch of ground with an area of 1 square meter receives about 1000 Joules every second. Sounds like a lot of energy, right? Well, setting aside the fact that this is only true in direct sunlight (and so by definition only during daytime), the issue is that most solar cells are only about 10% efficient. This means we can only extract about 100 Joules per second for every square meter of (generally expensive) solar cells that we build.
So, let's say we buy a 1-square-meter solar cell and collect sunlight for 1 hr. In the best case scenario, this will give us about 86 food calories' worth of energy. This is equivalent to half a granola bar, or about 3/4 of a Tablespoon of gasoline!
Conclusion:
Burning stuff like gasoline or coal releases a LOT of energy, and it's going to be hard to find other energy sources that are as cheap and energy-rich.
But that won't stop us from trying. In future posts, I will address the steps we are taking at MIT to try to come up with new ways to generate clean energy, and just as crucially, how to store and distribute it.
NOTES!
1. Some of you may be surprised that that much gasoline is actually required. (I was.) But the thing to keep in mind is that cars are actually quite inefficient when it comes to extracting energy from gasoline: for a typical auto engine, the average efficiency (amount of useful mechanical energy actually extracted divided by the total extractable amount) is around 18-20%. In fact, thermodynamics shows us that the best we can ever hope for with this kind of engine is around 37%. So, the "large" amount of gasoline required to drive one mile is not due to a limited amount of energy in gasoline, but due to the limitations on our capability to extract useful energy from it.
2. Source: Muller, R.A., Energy for Future Presidents. New York: W.W. Norton, 2012.
January 19, 2016
Electro-osmosis: Moving Water With Electricity
If you ever find yourself with a glass of water, two drinking straws of different diameters, and a little free time, you might notice that if you drink out of the smaller drinking straw, you don't get as much water as you do with the larger one. In other words, if you want to drink water at the same rate through each straw, you need to exert more effort when drinking out of the smaller straw. In general, the smaller the straw, the more effort (i.e., pressure) it takes to drive fluid at a given rate through it. This principle makes good intuitive sense, and is predicted by the mathematical equations that govern fluid flows. Perhaps a little interesting, but nothing special. Why does it matter?
It matters if you work in microfluidics, which, true to its name, involves fluids flowing through extremely small passageways. These passageways are usually hundreds of times smaller than a drinking straw - usually about as big around as a human hair. So, from what you now know about the exciting world of drinking straw physics, you would suppose that we'd need a lot more pressure to make the water flow through a microchannel than a straw, if we wanted to push water at the same flow rate through the straw and the microchannel. And you would be right. The pressure demands for driving fluid through microchannels are significant (see note 1).
If you want to drink water out of a drinking straw, there is pretty much only one way you're going to get the water to go against gravity and creep upward through the straw toward your lips: exert pressure by creating suction with your mouth. How else could you do it, right? But if you want to drive water through a tiny microchannel, it turns out there is an alternative to using pressure that you don’t have when drinking out of a straw. On small size scales, there is a completely different way to make water flow.
Notes
1) Despite this, pressure-driven flow is still used in microfluidics when the required flow rate is not too high.
2) It is very important to note, though, that even though there are charged particles swimming around in your glass of water, there are (roughly) just enough that they cancel each other out. In a standard glass of water, there are about as many hydroxide (OH-) ions as there are protons (also known as H+ ions), so that you can think of any given droplet of water as being electrically neutral. There are about 60 million billion hydroxide ions in your 1-liter bottle of water as well. They are completely harmless and are present in every glass of water you drink.
It matters if you work in microfluidics, which, true to its name, involves fluids flowing through extremely small passageways. These passageways are usually hundreds of times smaller than a drinking straw - usually about as big around as a human hair. So, from what you now know about the exciting world of drinking straw physics, you would suppose that we'd need a lot more pressure to make the water flow through a microchannel than a straw, if we wanted to push water at the same flow rate through the straw and the microchannel. And you would be right. The pressure demands for driving fluid through microchannels are significant (see note 1).
If you want to drink water out of a drinking straw, there is pretty much only one way you're going to get the water to go against gravity and creep upward through the straw toward your lips: exert pressure by creating suction with your mouth. How else could you do it, right? But if you want to drive water through a tiny microchannel, it turns out there is an alternative to using pressure that you don’t have when drinking out of a straw. On small size scales, there is a completely different way to make water flow.
What if I told you that if you put two metal electrodes on opposite ends of a microchannel filled with water and applied some electricity, the water would instantaneously begin to flow from one electrode to the other? This is indeed what happens. It is possible to make water flow from one place to another in a microchannel using two pieces of metal and some electricity. That's all you need. No pumps or any other moving parts are necessary. This technique is very common and people in microfluidics use it every day.
What is going on here?
What is going on here?
More than H2O molecules
Let’s take a closer look at that glass of water. A much closer look. If you magnified a glass of water a few million times, you would discover a lot more than just H2O molecules swimming around. Among other things, in a typical glass of water there are also a vast amount of protons (the same protons that make up the nuclei of atoms) "swimming" freely about as well. How many protons? A 1-liter bottle of water contains about 60 million billion (6 times 10 to the 16th power) free protons (although there are many, many more H2O molecules than that - see note 2). Recall also that protons have a positive electric charge. This will be important in a moment.
Now that we know there are charged particles swimming around your glass of water along with the H2O molecules, let's look at what goes on at the interface between the glass and the water.
Let’s take a closer look at that glass of water. A much closer look. If you magnified a glass of water a few million times, you would discover a lot more than just H2O molecules swimming around. Among other things, in a typical glass of water there are also a vast amount of protons (the same protons that make up the nuclei of atoms) "swimming" freely about as well. How many protons? A 1-liter bottle of water contains about 60 million billion (6 times 10 to the 16th power) free protons (although there are many, many more H2O molecules than that - see note 2). Recall also that protons have a positive electric charge. This will be important in a moment.
Now that we know there are charged particles swimming around your glass of water along with the H2O molecules, let's look at what goes on at the interface between the glass and the water.
 |
| When glass is exposed to air, the silanol (SiOH) groups stay composed and mind their own business. However, whenever water is brought into contact with the glass, the SiOH molecules deprotonate (give up their protons), rendering the glass surface negatively charged. Protons from the bulk water solution flock to the surface to "shield" the charged surface, so that the region between the 2 red lines is electrically neutral. This layer of protons, along with the charges on the glass surface, constitute the electrical double layer. |
Glass is primarily composed of silicon dioxide (SiO2), but the outer surface of the glass, the part that "sees" the water, is made of a chemical compound called silanol. The formula for silanol is SiOH: one silicon atom, one oxygen atom, and one hydrogen atom bound together. A single grouping of these atoms is called a silanol group. The reason I bring this up is that whenever SiOH groups are brought into contact with a fluid that has a pH higher than about 3, they cannot hold on to their hydrogens anymore. Or, more specifically, they cannot hold on to the protons from the hydrogens (remember that a hydrogen atom consists of one proton and one electron), and the protons escape from the glass surface into the water, like a top hat blown off of an old man's head in the wind. This loss of protons does happen for a reason, but it is not really that important to the present discussion. The important thing is that this process happens whenever water and glass are brought into contact, and it is called deprotonation.
Positive Band-Aids
Deprotonation has some interesting consequences in a drinking glass-water system. Once the glass loses protons, its surface becomes negatively charged (see note 3). Nature would rather this didn't happen. It's a little like an open wound exposed to open air. Nature would like to apply a positively charged “band-aid” to the surface so that it becomes electrically neutral, which is the preferred configuration.
Now, remember the quadrillions of positively charged protons swimming around in the water? Recall that protons are positively charged, and as discussed above they are readily available. So it only makes sense that the protons act as the "band-aid" to the charged surface. And this is precisely what happens: some (not all) of the freely floating protons gather very (very) near the glass surface, "shielding" the negatively charged glass (see figure above). So the negatively charged "wound" is now covered with the positively charged "band-aid," and this band-aid is known as the Electric Double Layer (EDL). If all this sounds time-consuming, it's not. The whole process takes less than a millionth of a second. Something to think about the next time you pour yourself a glass of water.
Now, remember the quadrillions of positively charged protons swimming around in the water? Recall that protons are positively charged, and as discussed above they are readily available. So it only makes sense that the protons act as the "band-aid" to the charged surface. And this is precisely what happens: some (not all) of the freely floating protons gather very (very) near the glass surface, "shielding" the negatively charged glass (see figure above). So the negatively charged "wound" is now covered with the positively charged "band-aid," and this band-aid is known as the Electric Double Layer (EDL). If all this sounds time-consuming, it's not. The whole process takes less than a millionth of a second. Something to think about the next time you pour yourself a glass of water.
Now consider that microfluidic channels are often made from glass. So whenever we fill a microfluidic channel with water, the glass deprotonates, becomes charged, and attracts protons to its surface. By the way, the electrical double layer is extremely thin. If a microchannel the size of a human hair were magnified to the size of an average-size classroom, the EDL would be as thick as the paint on the walls.
Putting it all together
Putting it all together
Now for the reason why I've been rambling about protons in glasses of water all this time. Now let’s say you fill a glass microcapillary (basically a tiny hollow glass tube, about as big around as a human hair) with water. As always, there will be layers of protons shielding the glass walls. Now, take your metal electrodes and place them on either end of the channel and apply a voltage between them, i.e., make one electrode negatively charged with respect to the other. Remember that, as always, opposites attract. The protons in the EDL sense a positive and negative electrode in their midst. The protons, being protons, would much rather head towards the negative electrode, and that's what they do. The transport of protons (and indeed, any ions in an aqueous solution) in response to electricity is called electromigration.
Now, you might think that since protons are so tiny, they don’t exert any influence on the surrounding water when they move. Not so. When a proton moves in a fluid through electromigration, it “drags” the surrounding fluid along with it. Now, since protons are indeed incredibly small, one proton drags a minuscule amount of fluid. But remember that there are billions upon billions of these protons coating the walls of the microchannel. There are enough that you can think of the protons as a “sheath” that “coats” the microchannel edges. This proton sheath is substantial enough to drag the rest of the water in the microchannel along with it. The "micro-paint-thin" layer of protons drags the rest of the water in the "micro-room." Again, this process is extremely quick to get started, fast enough so that when you flip the switch, the flow has effectively reached full speed instantaneously.
Now, you might think that since protons are so tiny, they don’t exert any influence on the surrounding water when they move. Not so. When a proton moves in a fluid through electromigration, it “drags” the surrounding fluid along with it. Now, since protons are indeed incredibly small, one proton drags a minuscule amount of fluid. But remember that there are billions upon billions of these protons coating the walls of the microchannel. There are enough that you can think of the protons as a “sheath” that “coats” the microchannel edges. This proton sheath is substantial enough to drag the rest of the water in the microchannel along with it. The "micro-paint-thin" layer of protons drags the rest of the water in the "micro-room." Again, this process is extremely quick to get started, fast enough so that when you flip the switch, the flow has effectively reached full speed instantaneously.
 |
| Schematic of electro-osmotic flow. The arrows indicate the direction of the proton migration, and ultimately of the fluid flow. |
Thus, it is possible to move water through a microchannel by the simple application of electricity. This type of flow is generally known as electro-osmotic flow, or EOF, and it is used every day in microfluidics research and industry. It provides an alternative to using pressure to drive flow. It is a key component of capillary electrophoresis, an extremely useful technique used in analytical chemistry to separate different compounds out of a single sample. It is the basis for electro-osmotic pumps, which use EOF to “pump” water, generating sufficient pressures to do useful work using no moving parts. At MIT, we discover new uses for EOF almost daily, and the technique will likely continue to be useful for many years to come.
Notes
1) Despite this, pressure-driven flow is still used in microfluidics when the required flow rate is not too high.
2) It is very important to note, though, that even though there are charged particles swimming around in your glass of water, there are (roughly) just enough that they cancel each other out. In a standard glass of water, there are about as many hydroxide (OH-) ions as there are protons (also known as H+ ions), so that you can think of any given droplet of water as being electrically neutral. There are about 60 million billion hydroxide ions in your 1-liter bottle of water as well. They are completely harmless and are present in every glass of water you drink.
3) Incidentally, surfaces other than glass can and do become electrically charged when brought into contact with water as well. It turns out there are many different mechanisms for surfaces to become charged in the presence of liquids.
January 11, 2016
Doctoral Work, Part 1: Bi-metallic Nano-Swimmers
Let's say you were bored one day, and you had a bottle of hydrogen peroxide and a piece of platinum wire lying around. Let's say you wanted to find out what would happen if you dropped the platinum into the peroxide (you are really bored). What would you see? As soon as you drop the wire into the solution, a chemical reaction will immediately begin to occur that will cause tiny bubbles to form all over the metal surface (see note 1 below). Although bubbles would form, the wire would not move around in the container at all. Why would it, right? It would simply settle to the bottom. Similarly, if you dropped a piece of gold into the peroxide, it would not move.
But what if instead you dropped a microscopic metal cylinder made of half platinum and half gold into the peroxide? What would happen then? It would not be unreasonable to assume that the cylinder would act similarly to the individual platinum and gold pieces and simply settle to the bottom of the container. However, the actual result is quite different.
You see, it is possible to make these mini-cylinders, and they are known as 'bimetallic nanorods.' When immersed in hydrogen peroxide, bimetallic nanorods move entirely on their own at 10-100 body lengths per second. No outside driving force is required. The rods always move along their axis, and always with the platinum end forward (which is a clue as to how they move). For comparison, the Space Shuttle moved at a bit over 100 body lengths per second while achieving orbit.
Even though the rods move fairly fast relative to their size, it should be emphasized that "their size" is really quite diminutive. Bimetallic nanorods are typically about 2 micrometers (or "microns") in length and about 300 nanometers in diameter (see note 2). To get an idea of how small that is, consider that an average human hair has a diameter of about 100 microns. You would need to lay 50 nanorods end-to-end to equal the diameter of an average human hair.
If that doesn't convince you that these things are tiny, take a look at the picture below. That container has about 100 billion (1 followed by 11 zeros) nanorods in it (see note 3). And they're not even taking up the entire container - most of them are gathered in that dark smudge at the bottom.
So, how do bimetallic nanorods come in? It has been experimentally shown that nanorods are capable of attaching themselves to tiny spheres (1-micron diameter) made out of polystyrene (the same material that foam cups are made of) and tugging them around (see video below). One day we may be able to replace the sphere with a drug, and have the nanorods bind to the drug, seek out a certain site (e.g. a tumor) in the body and deliver the drug there (see note 4). One of the reasons that hasn't happened yet is that nobody has figured out how to make nanorods move in fuels other than peroxide. And the main reason that hasn't happened yet is that nobody knows exactly why they move in hydrogen peroxide.
Which brings us to the second question: how do bimetallic nanorods move in hydrogen peroxide?Until my work, a complete physical theory had not been formulated, but clearly it has something to do with the peroxide itself. Somehow, the nanorods are using it as a fuel - they convert the chemical energy stored in the H2O2 molecules into mechanical energy (motion) (see note 5). We know this because they barely move at all in pure water, and because their swimming speed increases with the concentration of hydrogen peroxide; that is, the more peroxide per unit volume you have, the faster the nanorods go. So the peroxide is definitely the energy source for the autonomous motion. Of course, humans can also move autonomously in water (i.e., swim), and we also do it by converting chemical energy (stored in the body) into motion (using our muscles). But nanorods don't have muscles - they're just microscopic pieces of metal! We know they get their energy from the peroxide, but how do they convert it into the mechanical energy that propels them forward?
That question is the subject of my thesis research. There are several prevailing theories behind the nanorods' motion, although it has not been proven which one, if any, is the correct one. We are currently formulating our own theory, which I am using a computer model to simulate. The goal is to successfully recreate the motion of a nanorod on a computer. We are also conducting our own experiments with nanorods. If the results of my simulations agree well with the experimental results found by our group and by other groups, that will constitute strong support for my model. We will be that much closer to being able to use nanorods in the human body and elsewhere in nanotechnology.
Notes
1. What is happening here is that the platinum is acting as a catalyst to initiate the chemical reaction. Remember that the chemical formula for hydrogen peroxide is H2O2. Roughly speaking, the platinum gives the peroxide molecules a little "nudge" that makes them "want" to break down into water and oxygen gas. The oxygen gas shows up as the bubbles you see.
2. Just as there are 1000 millimeters in 1 meter, there are 1000 micrometers in 1 millimeter and 1000 nanometers in 1 micrometer. The general rule is that if one feature on an object is less than 1 micron in length (in this case, the diameter), the nano- prefix is used, hence the name nanorods.
3. You might ask how we know there are that many nanorods in there. (We didn't count them!) The answer has to do with the method used to make them. Nanorods are actually grown by depositing metal into tiny pores in a membrane made of aluminum oxide. The inner diameter of the pores is about the same as the diameter of the nanorods. We know how many pores there are in a given area of the membrane, so for a membrane of any given size we can have a fairly accurate estimate of how many nanorods we made.
4. Targeted drug delivery was recently realized in a proof-of-concept experiment: some colleagues of ours at UC-San Diego used a different type of self-propelling rod (made of zinc) and administered orally to some rather unsuspecting mice. The nifty thing about these swimmers is that they use stomach acid as a fuel, and deliver cargo payloads into the stomach lining of some unsuspecting mice. For the technically inclined, the journal article is here, and you can read a non-technical press release here. This work is a major step forward toward the goal of using self-propelling particles to deliver drugs in nanomedicine.
5. By the way, there are naturally occurring nanoscale motors that are capable of doing a similar thing. For example, several different types of biomolecules are capable of harvesting energy from energy-rich molecules such as adenosine triphosphate (ATP) to initiate autonomous motion.
But what if instead you dropped a microscopic metal cylinder made of half platinum and half gold into the peroxide? What would happen then? It would not be unreasonable to assume that the cylinder would act similarly to the individual platinum and gold pieces and simply settle to the bottom of the container. However, the actual result is quite different.
You see, it is possible to make these mini-cylinders, and they are known as 'bimetallic nanorods.' When immersed in hydrogen peroxide, bimetallic nanorods move entirely on their own at 10-100 body lengths per second. No outside driving force is required. The rods always move along their axis, and always with the platinum end forward (which is a clue as to how they move). For comparison, the Space Shuttle moved at a bit over 100 body lengths per second while achieving orbit.
 |
| Diagram of a typical nanorod. The black arrow indicates the direction of motion. |
If that doesn't convince you that these things are tiny, take a look at the picture below. That container has about 100 billion (1 followed by 11 zeros) nanorods in it (see note 3). And they're not even taking up the entire container - most of them are gathered in that dark smudge at the bottom.
 |
| ~100,000,000,000 nanorods. Seriously. |
At this point, two good questions have probably occurred to you.
- Why should we care that these little cylinders can swim in peroxide? What can we do with them that would be useful or helpful?
- How in the world do they manage to move on their own? Why do they only move in hydrogen peroxide?
So, how do bimetallic nanorods come in? It has been experimentally shown that nanorods are capable of attaching themselves to tiny spheres (1-micron diameter) made out of polystyrene (the same material that foam cups are made of) and tugging them around (see video below). One day we may be able to replace the sphere with a drug, and have the nanorods bind to the drug, seek out a certain site (e.g. a tumor) in the body and deliver the drug there (see note 4). One of the reasons that hasn't happened yet is that nobody has figured out how to make nanorods move in fuels other than peroxide. And the main reason that hasn't happened yet is that nobody knows exactly why they move in hydrogen peroxide.
Nanorods can be steered using external magnetic fields and can also pick up and release cargo at pre-determined locations. Here, the cargo is a spherical polystyrene particle with a magnetic coating. When it gets close enough to the cargo, the rod snaps on in much the same way that magnets "snap" onto your refrigerator door.
That question is the subject of my thesis research. There are several prevailing theories behind the nanorods' motion, although it has not been proven which one, if any, is the correct one. We are currently formulating our own theory, which I am using a computer model to simulate. The goal is to successfully recreate the motion of a nanorod on a computer. We are also conducting our own experiments with nanorods. If the results of my simulations agree well with the experimental results found by our group and by other groups, that will constitute strong support for my model. We will be that much closer to being able to use nanorods in the human body and elsewhere in nanotechnology.
Notes
1. What is happening here is that the platinum is acting as a catalyst to initiate the chemical reaction. Remember that the chemical formula for hydrogen peroxide is H2O2. Roughly speaking, the platinum gives the peroxide molecules a little "nudge" that makes them "want" to break down into water and oxygen gas. The oxygen gas shows up as the bubbles you see.
2. Just as there are 1000 millimeters in 1 meter, there are 1000 micrometers in 1 millimeter and 1000 nanometers in 1 micrometer. The general rule is that if one feature on an object is less than 1 micron in length (in this case, the diameter), the nano- prefix is used, hence the name nanorods.
3. You might ask how we know there are that many nanorods in there. (We didn't count them!) The answer has to do with the method used to make them. Nanorods are actually grown by depositing metal into tiny pores in a membrane made of aluminum oxide. The inner diameter of the pores is about the same as the diameter of the nanorods. We know how many pores there are in a given area of the membrane, so for a membrane of any given size we can have a fairly accurate estimate of how many nanorods we made.
4. Targeted drug delivery was recently realized in a proof-of-concept experiment: some colleagues of ours at UC-San Diego used a different type of self-propelling rod (made of zinc) and administered orally to some rather unsuspecting mice. The nifty thing about these swimmers is that they use stomach acid as a fuel, and deliver cargo payloads into the stomach lining of some unsuspecting mice. For the technically inclined, the journal article is here, and you can read a non-technical press release here. This work is a major step forward toward the goal of using self-propelling particles to deliver drugs in nanomedicine.
5. By the way, there are naturally occurring nanoscale motors that are capable of doing a similar thing. For example, several different types of biomolecules are capable of harvesting energy from energy-rich molecules such as adenosine triphosphate (ATP) to initiate autonomous motion.
August 15, 2013
Speech at Graduation Ceremony
This is the speech I gave at my Ph.D. graduation ceremony at the University of Washington on June 16, 2013. There wasn't much of a prompt - I was essentially asked to simply say something inspiring to the students. I've been passionate about increasing the public's appreciation of science for a while now, so I decided to let loose with some of the thoughts that had been percolating in my head for the past few years...
----
My graduate school story is somewhat unique. I began working on the Ph.D. I am receiving today more than five years ago at Arizona State University in Tempe, where the temperature as currently around the melting point of lead. I started working for Jonathan Posner (sitting over there), as an undergraduate way back in 2006, and stayed with him all the way through grad school. So now, in 2013, my working relationship with my advisor has lasted longer than quite a few marriages do. But now we're separating amicably. [to Dr. Posner] I'm sorry...I need to move on. [his response: "The feeling is mutual."]
Anyway, I wrote my dissertation on tiny metallic wires that propel themselves. They don’t have
any moving parts, they’re just little pieces of metal. But somehow, they move when you add hydrogen
peroxide to the solution. I saw a
lecture about them, and I thought it was interesting that nobody had tried to
rigorously understand why they move, and so I investigated, and investigated
some more, and after a while it was my project.
Then, 2 years ago, almost to the day, Dr. Posner
told the research group that he was moving to the UW, and he wanted all of us
to come with him, and I’m standing here, so I guess you know my answer. I was excited to move to the Northwest and
study here at UW, and I’ve enjoyed taking courses in our lovely ME department,
as well as expanding my scope by taking courses in applied math. With a patient and understanding girlfriend
back in Phoenix, it was a tough decision, but I’m glad I made the move.
But now it’s over.
And here we all are. We did it. Today I’m
asking myself the same question I’m sure many of you are: why did I do this? Was this worth it? How have I evolved as a person since I
started school? I can’t speak for all of
you, but I would argue that one of the biggest things, if not the biggest
thing, that I got out of grad school was what happened outside of the lab. Let me tell you a story.
Right as I was beginning graduate school, I first
heard about a guy named Brian Greene, who is a theoretical physicist at
Columbia University. He wrote a book
about his own specialty, string theory, for the general public called The Elegant Universe. I didn’t know too much about string theory,
only that it was incredibly abstract and mathematical. And yet Greene managed to make it fun. He managed to convey the basics of one of the
most abstruse theories of particle physics without showing a single equation. I was captivated, not only as a scientist,
but as a person. At the same time, he
was getting ready to launch the inaugural World Science Festival, similar to
the Seattle Science Festival that’s just wrapping up. Long story short, I began reading his other
books, watched his TV specials, and I eventually paid for my own plane ticket
to fly to New York City to participate in the WSF.
One of Professor Greene’s main messages, that I have
come to agree with over time, is that more and more, science is playing a
fundamental role in daily life, and yet the public’s awareness and appreciation
of science is not necessarily commensurate with their dependence on it.
This audience is all too familiar with many of the
issues humanity is currently facing: what to do about climate change, alternate energy sources, nuclear proliferation, the consequences of GMO food, the possible future of humanity in space, potential asteroid impacts, treating diseases like tuberculosis and diabetes; what do these have in common?
These issues, at their core, are scientific problems. They are not political issues or moral issues. They are
scientific. And as we know, scientific
problems demand scientific solutions. There’s
a lot of debate (and hype) swirling around these issues, but oftentimes the
science is cast aside, in the periphery of the discussion at best. But the science is what should inform what we
do. That especially applies to the
policymakers who ultimately determine, to a large extent, what we will
do.
So what can we, as the latest graduating class in
mechanical engineering at the University of Washington, do about these problems?
I would say that the people on the front lines of
science and engineering, you and I, should strive to be communicators of what
we do. Now, of course you will
communicate as an engineer; it’s a fundamental aspect of the job. When I say communicate, I don’t just mean sending
technical reports to your boss or publishing journal articles. I mean talking to the public. And I don’t just mean being willing to talk
to the public, I mean actively seeking out opportunities to do so. It is
up to us to make sure what we do is presented effectively and accurately to
non-scientists. I would like to see
scientists getting more involved in public life.
An example: the US House Science Committee currently
consists of 40 members. That includes 14
attorneys, 8 who work in business, 4 physicians, 4 career politicians, 3
educators, 3 real estate executives, 1 rancher and 1 career military
officer. Only Thomas Massie, a
Republican from Kentucky, has bachelor’s and master’s degrees in engineering from
MIT. He sits on the Subcommittee on
Energy. But what if we had an atmospheric
scientist serving on the Subcommittee on the Environment? How about a rocket propulsion-trained
aerospace engineer on the Subcommittee for Space?
Communicating science to the public isn’t always
easy, but it benefits the communicator too.
Even for someone like me, who’s been doing math and science for most of
my life, being a communicator has helped me to rediscover the joy and meaning
of being a scientist and engineer. Science
is vital to a full life, just as literature, art, music, and theatre are.
So today, as you celebrate, think about how you
could bring your work to a wider audience.
Let’s share what we do with the world.
Let us strive not just to be the best engineers we can, but to be the
most effective communicators we can.
Because in doing so, we will become better engineers.
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