Blowing up the brain

Baby-diaper chemistry offers scientists a better view of our brains’ wiring

Blowing up a photo can show its details better. In the same way, enlarging a sample of brain tissue can help reveal the bigger picture of how cells in our brains are wired. A chemical similar to one found in baby diapers now gives scientists a new way to do just that.

 

For many years, disposable baby diapers have contained crystals nestled in their soft lining. Those crystals are a type of “super slurper” chemical known as sodium polyacrylate. It’s a polymer, or molecule made from long chains (hence the poly in its name). Decades ago, chemists learned that when these super-absorbers make contact with water, they suck up the liquid. Suddenly, what had been a powder made from crystals becomes a big gob of moist gel.

 

Over the years, chemists have turned super slurpers loose to tackle a host of problems beyond leaky diapers. For example, they can help pick up hazardous chemicals after a terrorist attack. But until now, nobody imagined their use in viewing the brain.

 

Credit that to a team of scientists at the Massachusetts Institute of Technology in Cambridge. They harnessed super slurpers for what they’re calling “expansion microscopy.”

 

It’s a bit like drawing a picture on a balloon’s surface, explains Edward Boyden, a neuroscientist at MIT. Blowing up the balloon makes the drawing bigger. “That’s what we were trying to do, but with a three-dimensional object like the brain.” By attaching the super slurper to molecules throughout brain cells and then adding water, the Boyden’s team can enlarge a sample of tissue to about 100 times its original volume.Science published details of the team’s technique online on January 15.

How it works

Typically, microscopy uses light and lenses to make tiny features appear bigger. Here, the team took something tiny and looked for a way to make it swell up so that it would become physically bigger.

 

The team starts by soaking a piece of preserved brain tissue in a solution with lots of the super slurper’s building blocks. “Then we add a second chemical and these building blocks start to form into long chains called polymers.”

 

This polymer attaches itself to molecules throughout neurons — nerve cells — in the tissue sample. Before long, the tissue has “all these little thin wires of polymer that are winding their way through it,” Boyden explains. It’s like the tissue has become “embedded in a sponge almost.”

 

That polymer is similar to the super slurper in diapers. “When you add water, it swells. And the brain gets bigger,” Boyden says.

 

Think about the spots on the surface of a polka-dotted balloon. When the balloon is deflated, the dots appear close together. But as it inflates, those dots begin to move farther apart. So it is with brain cells. “All the molecules in the brain get pushed away from each other,” Boyden says. Although the cells break apart, the expanded brain still has all of the same proportions as the original tissue.

 

The process also expands the spaces between neurons, called synapses. Chemical messages shoot across those synapses.

 

While some neurons can be centimeters long, synapses are usually “nanoscale,” Boyden says. They’re 100 billionths of a meter long or less.

 

With the new method, though, the synapses expand. As a result, researchers can see at the same time both big features, such as neurons, and previously nanoscale things like synapses.

 

Many scientists want to see parts of the brain more clearly, says Zayra Millan. A neuroscientist at Johns Hopkins University in Baltimore, Md., she did not work on the new project. “Expansion microscopy, which enlarges and fixes the specimens, is a novel way to do this,” she says.

 

“In an enlarged specimen, where local and long-range circuits are labeled, we have better visual access to the details,” she told Science News for Students. The ability to trace nerve fibers along their routes could help scientists trying to understand the brain and how different traumas alter it, she notes.

 

The new technique also could be a big step forward in helping scientists map the brain, Boyden says. “We can actually follow these neurons and see how they wire up.”

 

Fonte: https://student.societyforscience.org/article/blowing-brain

This ‘smart’ self-cleaning keyboard is powered by you

The bonus: It works for its owner and no one else

 

 

Rob Felt, Georgia Institute of Technology

 

A new keyboard can tell if you’re its owner. It locks out anyone else, even if that person knows your password. What’s more, this device needs no batteries. It harvests all the energy it needs from the action of your typing.

 

All in all, “This will hugely improve the security of a computer,” predicts Zhong Lin Wang. He’s a materials scientist at the Georgia Institute of Technology in Atlanta and a co-designer of the new keyboard.

 

“Our fingertips have electrostatic charges,” explains Wang. That means there’s an imbalance of electrons. Your fingertips generally have a slight positive charge. So they have somewhat fewer electrons than the area around them. And that principle makes it possible for typing to induce an electric current in the keyboard, Wang points out.

Just as the closely spaced bumps on a lotus leaf (shown here) repel water, the nanowires on the new keyboard’s keys repel dirt, oils and liquids.

stedenmi/iStockphoto

 

To understand how this works, consider a magnet. At one end is a positive charge. At the other is a negative charge. Opposite poles attract. So if you put the positive end of one magnet next to the negative one of another, they will latch onto each other. A similar idea applies to electrostatic charges. Positive charges attract negative ones.

Wang’s group put two layers of metal electrodes under the keyboard’s plastic surface. When a finger approaches a key, it attracts free electrons to the top electrode. The bottom electrode supplies them. As soon as the finger lifts off of the key, the electrons flow back to the lower electrode. Any flow of electrons creates an electric current.

 

And this induced electric current can power the keyboard — but only if the current is strong enough. To achieve that, the Georgia Tech team focused on nanotechnology.

 

(“Nano-“ refers to things measured on the scale of 100 billionths of a meter or less.)

 

The keys of the new keyboard are made of the same inexpensive plastic that might be found on any other standard keyboard. But instead of being smooth, the keys have millions of tiny plastic “nanowires” on their surface. Those nanowires make the new keys special. They add more surface area to every key, increasing the effective contact area between the plastic and the fingers, Wang explains. This ensures that there’s enough power to run the keyboard as someone types.

 

Because fingers touch the keys and then back off, that current isn’t constant. It also varies with the force and speed at which a typist strikes different keys. And that rate, force and pattern of typing will differ from one person to the next. In much the same way that a voiceprint gives a unique signature to the way each person speaks, typing will give a personal signature to each person’s keyboard use.

 

What this means, Wang explains, is that “even if the same phrase is typed by three different people, the [electrical] output signals are very different.” Thus, typing can be a type of biometrics — a way to identify people based on unique biological features.

 

The keyboard records information about the typing pattern and sends it to a program in the computer. The program then checks to see if the pattern matches the right user. If not, an alarm sounds, and the computer locks the typist out.

 

The new keyboard is also self-cleaning. All the tiny nanowires on the keys repel water, oils and dirt. It’s the same principle that lets a lotus flower float on a lake. The lotus has tiny water-repellant nanobumps covering its leaves.

 

Liming Dai is a polymer scientist who works with nanotechnology at Case Western Reserve University in Cleveland, Ohio. He did not work on the new keyboard, but he thinks the design could be important in getting better performance from a variety of devices.

 

“It could also be applied to a touch screen,” for instance, Dai says. Then smartphones and notepads could harvest energy from the motion of someone typing or drawing. And these devices could also benefit from the same keystroke “fingerprint” concept to keep strangers from using them. The smart keyboard might even be made from flexible polymers to create a medical sensor.

 

Future work might make the keyboard even more useful, Dai adds. A later design might build tiny capacitors onto the nanowires, he suggests. Capacitors are little devices that temporarily store an electric charge. Those might then power light-emitting diodes, or LEDs, to light a keyboard in the dark.

 

Meanwhile, Wang’s team has built a working prototype of its keyboard. If a company decides to fund its production, this keyboard could be in stores in as little as two years, says Wang.

 

His group published details on the design of its new keyboard in the January 27 issue of ACS Nano.

 

Fonte: https://student.societyforscience.org/article/%E2%80%98smart%E2%80%99-self-cleaning-keyboard-powered-you