Sightlines

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Microcapsules_credit_Chrysoula-Litina

The world uses twice as much concrete every year as steel, aluminum, plastic, and wood combined. Concrete is tough, easy to work with, and durable—but nothing lasts forever. In 2013, the American Society of Civil Engineers estimated that it would cost more than $3.6 trillion by 2020 to bring U.S. infrastructure up to good repair.

Now scientists and engineers at three British universities—Bath, Cambridge, and Cardiff—are teaming up to create new types of “smart” concrete. Inspired by biological processes that help skin regenerate, these materials could heal themselves by oozing to fill in holes or by stretching to quickly cover cracks.

At Cambridge, Abir Al-Tabbaa and her colleagues have created microcapsules containing mineral-based healing agents that act like scar tissue in human bodies. The capsules would be mixed into cement before pouring, and when the first tiny crack appeared in a concrete structure, admitting air and water, the plastic microcapsules would split open. This would deliver a dose of sodium silicate, a compound used to make cardboard and treat water.* The process would reoccur whenever concrete became stressed or damaged. Al-Tabbaa hopes the mineral repairs would last 20 years, greatly extending the life spans of man-made structures.

Meanwhile, at Bath, scientists are experimenting with adding bacteria and nutrients to concrete. When activated by water leaking into cracks, the bacteria would function as tiny mineral-producing factories, sending calcium compounds to plug gaps. And at Cardiff, researchers are working with shape-memory polymers—plastics that can shrink, grow, or twist when exposed to heat. Incorporating tendon-like strips of these polymers into concrete could help close large cracks if coupled with, say, a heat-blowing machine.

The first “smart” concrete bridge, road, or office block isn’t likely to be built anytime soon. Scientists must first figure out which technology works best under different conditions and test, among other things, ways to ensure that microcapsules are both fragile enough to burst when needed and tough enough to survive a cement mixer. But the concrete world could eventually become, at least on the inside, a little more human.

Safer Seas

When the Deepwater Horizon offshore oil rig exploded in 2010, underwater robots sent to seal the well had difficulty repairing the equipment, allowing oil to spew into the Gulf of Mexico for 87 days. That’s because humans controlling the robots from nearby ships had a hard time: Underwater currents swayed the bots, and there were lags between pressing buttons above water and seeing movement down below. What’s more, because the operators relied on video cameras to see the damage, they were stymied by murky or oily water.

BluHaptics, an American company, may have a fix for future spills: a system that uses sonar to build 3-D images of the seabed, allowing robots to function even in zero visibility. The technology also has touch-sensitive feedback; operators can use joysticks to feel what a bot is sensing—for example, a metal pipe.

This could do more than help stanch oil leaks. The system could also transform underwater archaeology, a field in which a delicate touch is required to avoid damaging long-submerged historical artifacts. BluHaptics’s technology, which has been in development for the past few years, is now undergoing field tests.

All in Your Head

To study and treat conditions like epilepsy and Parkinson’s disease, doctors sometimes embed electrodes within a patient’s brain. This allows them to see how the brain is functioning and to occasionally deliver stimulation that can ease tremors, pain, and even depression. Such implants, however, require wires running through the skull—opening a path for dangerous infections—so they’re only used as a last resort.

Enter Joshua Smith, a computer science professor at the University of Washington, who has been developing a fully wireless solution for the past few years. His system relies on one chip and two tiny devices that transfer power through “resonant coupling,” a technique used in some smartphone chargers: Two metal coils a few centimeters apart operate at the same electrical frequency and exchange energy.

In Smith’s design, a transmitter coil, only about 3 centimeters in diameter, is taped to a person’s scalp. It beams power through the head to a slightly smaller implanted receiver coil; this one runs a sensor measuring the brain’s electrical activity. To then send that data back to doctors, Smith created a new type of “backscatter” technology. Imagine a hiker signaling rescuers by using a mirror to reflect the sun. Similarly, a backscatter chip, embedded in the brain next to the receiver coil, delivers data by reflecting some of the signals broadcast by a small Wi-Fi unit that is carried or worn outside the body.

If a patient has a seizure, doctors could use Smith’s device to know exactly which areas of the brain are malfunctioning and more effectively target treatment. After promising lab trials, animal tests are slated for later this year.

Rainbow Warriors

The premise of camouflage—you can’t shoot what you can’t see—hasn’t changed over time, but its patterns certainly have. And the U.S. Army doesn’t always hit the mark: In 2004, it adopted a new, pixelated design that soldiers hated. They cited strange optical effects that actually made them stand out more at a distance.

But what if camouflage simply shifted as needed to blend into its surroundings? Scientists at the University of California, Berkeley, funded by the U.S. Defense Department, have made a high-contrast, flexible material that promises to switch to new colors and patterns in the blink of an eye.

Their lab demo, which they debuted in late 2014, employs the same transparent polymer used to make contact lenses. This material is etched with rows of tiny ridges that, at a certain distance apart, reflect a specific wavelength of light and thus determine the material’s color. By stretching the polymer slightly on a microscopic scale, the distance between the ridges changes, and the color shifts along with it.

So far, scientists have only created a 1-square-centimeter, manually adjustable swatch—not even enough to camouflage a toy soldier. If all goes according to plan, however, military uniforms made of the material could incorporate tiny electronic devices to cause stretching; wearable cameras could perhaps even sense the environment around a soldier and prompt automatic adjustments.

*Correction, June 11, 2015: The microcapsules that would be mixed into cement before pouring would deliver a dose of sodium silicate. Any earlier version misstated that they would deliver a dose of methyl methacrylate.

 Courtesy of The Optical Society in conjunction with UC Berkeley

Mark Harris is a freelance journalist based in Seattle.

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