One does not accidentally discover the transistor device, but must carefully construct a semiconductor structure with high purity and low defect density so that the amplification process can be observed. The hard work and innovative experimental techniques that enabled John Bardeen, Walter Brittain, and William Shlockley at Bell Laboratories in Murray Hill, New Jersey, to construct the world’s first transistor, led to their winning the Nobel Prize in physics in 1956 for this work. On the day Bardeen learned that he had been awarded his second Nobel Prize (in 1972, for his development of a theory for superconductivity), his transistorized garage-door opener malfunctioned, underscoring the need for continuing research in solid-state physics.
As manufacturing and quality-control techniques improved, and newer and smaller designs for transistors became available, another important application for this special electron valve was realized. With a small input current applied to the transistor, a small output current results. A relatively modest increase in the input current creates in turn an amplified, larger current. The output of the transistor can be either a “low current” or a “high current”; a low current is termed a “zero,” whereas if there is a high current, then this state is labeled a “one.” Minor adjustments to the inputs to a transistor can create either a one or zero for the output current. By combining literally millions of transistors in clever configurations, and making use of a branch of mathematics called Boolean logic (developed by a mathematician named George Boole more than ninety years before the transistor was invented and seventy years before Schrödinger’s equation was developed), one has the basic building block of a microcomputer.
A full discussion of how computers manipulate “ones” and “zeroes” to represent larger numbers and carry out mathematical operations through binary code would require another, separate book. The point I want to make here is that at the heart of all microcomputers and integrated circuits is the transistor. The “chips” that underlie the commercial and recreational electronics that play a larger and larger role in society, from cell phones to laptop computers to DVD players, are all simply platforms for the clever arrangement of, and connections between, a large number of transistors. The computerized and wireless technology that surrounds us in the twenty-first century would not be possible without the transistor, which in turn could not have been invented without the insights previously gained by the pioneers of quantum physics and electromagnetism.
Schrödinger was not trying to develop a CD player, or even replace the vacuum tube, when he developed his famous equation, but without his and others’ investigations into the properties of matter, the modern lifestyle we enjoy today would not be possible. All of our lives would be very different if not for the efforts of a relatively small handful of physicists studying the behavior of the natural world. With few exceptions, these scientists were driven not by a desire to create commercial devices and practical applications, but by their curiosity, which led them, as Dr. Henry Pym put it in Tales to Astonish # 27, to “work only on things that appeal to [their] imagination.”
25
THE COSTUMES ARE SUPER, TOO—MATERIALS SCIENCE
THROUGHOUT OUR DISCUSSIONS of physics principles, we have been fairly liberal in dispensing “one-time miracle exceptions” to the laws of nature in order to account for a wide variety of superpowers—such as running at superspeed, altering temperature gradients in the atmosphere, or shrinking down to the size of an atom. Now we must take up one final suspension of disbelief, without which no superhero can reliably and safely use their powers. I speak, of course, about the miracle of superhero costumes!
Consider the Avengers and the Justice League of America, assemblies of superheroes in the Marvel and DC universes respectively. While the Avengers’ membership has evolved over time, typical members include Captain America, Hawkeye (the Green Arrow of Marvel comics), Giant-Man, the Wasp, Iron Man and the mighty Thor. Similarly, the roll call of the Justice League was not fixed, but often listed as members Superman, Batman, the Flash, Green Lantern, Green Arrow (the Hawkeye of the DC universe), Aquaman, the Atom, and Wonder Woman. Before the Avengers can save the world from Kang the Conqueror, the Masters of Evil, or Ultron, or before the JLA can stop such foes as Starro, Despero, or Amazo, these heroes first have to dress for success. One can’t go around avenging or forming a league for justice if one’s costume is a shredded pile of rags or a loose pile on the floor after one has changed shape and size. After all, the Comics Code Authority frowns on embarrassing “wardrobe malfunctions.”78
Fortunately, the question of the composition of superhero costumes that enables one to employ amazing powers and abilities—without risking an “adult warning label” on the cover of the comic book—was addressed in early issues of the first family of Marvel comics—the Fantastic Four. Recall that in the Fantastic Four, the Human Torch has a uniform that remains undamaged when he bursts into flame; the Invisible Woman’s suit turns transparent when she does; Mr. Fantastic has a jumpsuit that can stretch like rubber and return to its original shape when he resumes his normal form; and Ben Grimm, the orange, rocky, superstrong Thing, has little blue shorts.
When the Fantastic Four made their comic-book debut in November 1961, they initially wore plain civilian clothes, as they needed to fly under the radar in both the comic-book and real worlds. The quartet had to sneak onto a military base in order to surreptitiously fly a rocket ship Reed had designed in order to beat the Russians in the space race—a test flight that would lead to their exposure to superpower-granting cosmic rays. Similarly, Marvel Comics kept a low profile on the costumed-hero front when the Fantastic Four first appeared. They depended at the time upon their competitor, National Periodicals (home of Superman, Batman, and the Justice League of America) for newsstand distribution. Marvel had, up till then, published Western, young-teen hijinks, and giant-monster comics. In order to not alert National that Marvel was encroaching on their superhero turf, the Fantastic Four fought the Mole Man and alien Skrull invaders in their street clothes in their first two issues. By issue # 3 they had donned blue jumpsuits that effectively became their superhero costumes. The fashion designer to the superpowered in The Incredibles, Edna Mode, would probably disdain the Fantastic Four’s “hobo suits,” but their outfits are able to mimic the FF’s powers, enabling them to use their special powers without wear and tear on their clothing. How do their uniforms do it? As described in Fantastic Four # 7, they are composed of one of Reed Richards’ miracle inventions: “unstable molecules.” No doubt Reed has shared the formula for such an amazing fabric with his Avengers comrades.
Now, any veteran of a high-school chemistry lab class knows that unstable molecules do indeed exist. These are the molecules that that fall apart or explode—precisely because they are unstable! But is it physically possible for real clothing to alter its thermal and structural capabilities in response to the wearer’s needs? The answer is: yes! Shape-memory materials, technically known as thermoresponsive materials, “remember” their original configuration, so that after being bent or deformed, they can return to their original shape. These materials undergo a phase transition with changing temperature, pressure, or applied electric field (as in Gotham City’s crusader’s cape in the film Batman Begins), enabling applications from the familiar (shrink-wrap) to the exotic (surgical knots that self-tighten). Unlike melting or boiling phase transitions, these materials undergo transformations between differing crystal structures.
Before we consider designing clothing using shape-memory materials, we should ask a more basic question: What is it that determines an object’s “shape?” The properties of any solid are governed by two factors: its chemical composition and the arrangement of its atoms.
Consider carbon atoms, the super-flexible Mr. Fantastic or Elongated Man79 of the periodic table of the elements. Unlike most atoms, which rarely deviate from the preferred number of chemical bonds they will form with other atoms, carbon is particularly malleable in the number and type of chemical bonds
it can assume. As discussed in Chapter 21, chemical bonds between atoms in molecules or solids result only when the electronic waves in the individual atoms are such that, when they overlap, “harmonics” of a sort arise that lower the total energy of the resulting bond, compared with the two separate atoms. When the bound atoms are in a lower energy configuration, we must supply external energy, such as heat or light, in order to separate them. When breaking apart a molecule, this energy is called the “binding energy.” For phase transitions, such as when liquid turns to a vapor, the heat we must provide to effect the transformation is termed the “heat of vaporization,” while before a solid melts we must add a “heat of fusion.”
Carbon achieves the greatest lowering in energy when it forms four chemical bonds, but it can do so in many different ways. It can form two strong bonds with other carbon atoms in a long line, and other types of atoms at sharp angles to the linear sequence, as in long-chain polymers such as proteins or DNA. It can form three strong bonds with other carbon atoms in a single plane, forming hexagons of carbon atoms, as we saw in fig. 38 in Chapter 23. The carbon atoms then try to form a fourth bond with the atoms in the planes above and below them. As they can form a solid bond only with either the atoms above or below, but not both, the result is very strong bonds within each plane, and rather weak ones between the planes. The planes of carbon atoms then stack into thin sheets, one atop another, like phyllo dough in delicious baklava. In this case, we call the form of carbon “graphite,” and the fact that this solid is mechanically soft, with the layers easy to peel apart, makes it ideal for pencil “lead.” Whenever you write with a pencil, you are literally unraveling a carbon crystal, layer by layer.
Alternatively, the carbon could form four strong bonds with other atoms residing at the corners of a pyramid, with the original carbon atom at its center. If the central carbon atom binds with hydrogen atoms, then we call the resulting molecule methane gas. However, if the other atoms are also carbon atoms, the resulting solid is called “diamond.” Both graphite and diamond are composed of pure carbon, but the opaque, electrically conducting and easily deformed nature of graphite results from the carbon atoms stacking in sheets, while rearranging the carbon atoms into a tetrahedral configuration produces the transparent, electrically insulating, and very hard and rigid structure of diamond.
In Chapter 15, we described how the phase of a material, whether gas, liquid, or solid, depends on the temperature and pressure. Temperature measures the average energy per atom and determines whether the atoms have enough kinetic energy to unbind into the vapor phase, for example. By squeezing on the material—that is, by increasing the pressure—we may make it harder for the atoms to vaporize, and thus a higher temperature is required to execute the phase transition. There is a balance between energy and entropy that determines at what temperature and pressure a particular material will undergo a phase transition.
Under great pressure and elevated temperatures, graphite can be transformed into diamond, as when Superman wishes to give an engagement ring to Lois Lane. Less extreme efforts are required to transform shape-memory materials from one configuration to another. Here, the phase transition involves the material shifting from one particular arrangement of atoms (called a crystalline configuration) to another. The number of atoms in the material does not change, but if the material is distorted from its previous configuration, it may require additional energy to allow the atoms to move back to their previous arrangement.
Liquid crystals are a familiar example of materials that undergo a phase transition from one crystalline configuration to another, accompanied by a variation in structural and optical properties. Liquid crystals are actually long-chain carbon molecules. Electric forces between molecules can induce them to all line up in one direction, or to self-organize into layers. The forces that lead to this ordering are weak enough that the system still flows like a liquid. The application of an external electric field can shift certain liquid crystals from one ordered configuration to another. The ability of the liquid crystal to reflect light can change dramatically depending on the arrangement of the long-chain molecules. That is, in one phase, the liquid crystal may reflect most of the light that hits it (so it will look bright), while in another phase, it will absorb light, appearing dark. Behind every liquid-crystal pixel on a flat-screen television or computer monitor are electronics, including thin film transistors, that generate a varying electric field to change the optical properties of the pixel. The procedure by which alterations on the optical properties of the pixels are translated into a moving image is the same as described in Chapter 20.
Shape-memory materials are not always long chains of molecules, nor are they necessarily composed of carbon. Rather than inducing a phase transition with an electric field and temperature as in the case of liquid crystals, shape-memory materials undergo a transformation from one crystal structure to another under stress or pressure. Flexon or Nitinol are the commercial names of nickel-titanium alloys that exhibit high elasticity and memory aspects, making them useful for eyeglass frames and other applications. Nitinol was discovered accidentally in 1961 (the same year the Fantastic Four burst upon the scene) when a research-group leader at the Naval Ordinance Laboratory passed a bent sample of a newly synthesized alloy around for inspection to the scientists at a laboratory management meeting. One of the researchers decided to warm up the twisted metal using his pipe lighter (if there’s one thing I’ve learned from reading comic books, it’s that all scientists smoke pipes, or at least they did back in the Silver Age). All were surprised to see that upon warming, the bent alloy snapped back to its original configuration, and Nitinol (the “nol” in Nitinol derives from the initials of the Naval Ordinance Lab, while the “Ni” and “ti” standing for nickel and titanium) was launched. Bending the wire changed the alloy’s crystal structure, and the application of thermal energy from the pipe lighter enabled the metal to return to the lower-energy (more stable) crystal structure and regain its original shape. Varying the ratio of nickel and titanium in the alloy can alter the temperature at which the phase transition occurs. Nitinol wires are also employed in certain orthodontic applications: The wire is bent to fit inside a patient’s jaw and clamped in place. When warmed by body temperature, the wire exerts a steady pressure as it tries to return to its original shape, thus aligning the teeth.
Flexible shape-memory polymers have been around longer than their metallic counterparts. A familiar example is shrink-wrap, which undergoes a structural change upon warming. Here, certain chemical groups that cross-link and connect the long-chain molecules can soften upon an external trigger, such as an electric field or temperature, allowing the molecules to reorient themselves into a lower-energy configuration. In 2002, Andreas Lendlein and Robert Langer reported in Science their discovery of a biodegradable shape-memory thermoplastic polymer for surgical applications . When formed into a loose knot, threads of this material self-tighten when warmed to 104 degrees Fahrenheit, enabling endoscopic surgery with smaller incisions. Shape-memory alloys can be used in stents, catheters, and probes, following the narrow passageways in the body as easily as the Elongated Man would be able to follow these twists and turns.
While the functional jumpsuits and uniforms of the Fantastic Four and Avengers remain confined to the four-color pages of comic books, flexible shape-memory materials have recently been incorporated into real-world clothing. Certain fabrics expand in response to a lowering of temperature, so that when used as the inner layer in a winter jacket, they automatically increase the air gap, thereby improving thermal insulation. Other materials become more porous at higher temperatures, allowing body heat and water vapor to escape. Polymer-based fabrics have been developed that can be stretched to more than twice their normal length, and yet return to their original proportions when warmed. These materials may provide the answer to an age-old mystery: What holds up the Hulk’s pants?
The Hulk was a founding member of the Avengers, though he wore purple shorts dur
ing his brief tenure with the team. More typically, he battles the U.S. Army, the Abomination, or the Leader while wearing only a pair of purple pants. When nuclear scientist Robert Bruce Banner was belted by gamma rays, he gained the ability to transform from a puny nuclear scientist into an eight-foot-tall, two-thousand-pound Jade Giant. This metamorphosis rends all of Banner’s clothing—his shirt is shredded, his feet tear his shoes and socks apart, and the cuffs of his pants are frayed following his transformation to the Hulk, but his vast waistband remains intact. Presumably, his lavender Levi’s are composed of Reed Richard’s unstable molecules in the comic-book world, or shape-memory fabrics in ours.
The Hulk first appeared in his own Marvel comic in 1962, following the success of the Fantastic Four. Unfortunately, the Hulk might be the strongest there is, but his sales weren’t, and, his comic was canceled after only six issues. You can’t keep the Jade Giant down, and he returned a year and a half later in Tales to Astonish # 60. One can only imagine what the sales would have been if the Hulk’s pants had not managed to survive his many transformations. But here ol’ Greenskin was stymied by a force even he could not smash, stronger than gamma radiation: the Comics Code Authority!
The Physics of Superheroes: Spectacular Second Edition Page 34
