System Bits: Feb. 17

Can you hear light?
Silicon photonics has gained increasing attention as a key driver of lab-on-a-chip biosensors and of faster-than-electronics communication between computer chips. The technology builds on tiny structures known as silicon photonic wires. The wires work because light moves slower in the silicon core than in surrounding air and glass. Thus, the light is trapped inside the wire by the phenomenon of total internal reflection. The issue is that one light beam cannot easily change the properties of another. This is where light-matter interaction comes into the picture.

Researchers from the Photonics Research Group of Ghent University and imec have report on a peculiar type of light-matter interaction. They managed to confine not only light but also sound to the silicon nanowires. They realized that the sound cannot be trapped in the wire by total internal reflection. Unlike light, sound moves faster in the silicon core than in the surrounding air and glass. Thus, the scientists sculpted the environment of the core to make sure any vibrational wave trying to escape it would actually bounce back.

Both light (left) and sound (right) are trapped in a nanoscale silicon core. (Source: IMEC)

Trapped in that incredibly small area, the light and vibrations strongly influence each other: light generates sound and sound shifts the color of light, a process known as stimulated Brillouin scattering. The scientists exploited this interaction to amplify specific colors of light.

Their results were published in Nature Photonics this week and they anticipate that this will open up new ways to manipulate optical information. Light pulses could be converted into sonic pulses and back into light.

Eternal data storage
ETH Zurich researchers have found a way to store information in the form of DNA, preserving it for nearly an eternity.

In the search for ways to store data permanently, ETH researchers have been inspired by fossils. (Source:ETH Zurich)

In our digital era, a large part of our collective knowledge is located on servers and hard drives. It will be a challenge for this data to survive 50 years, let alone thousands of years. As such, scientists at ETH Zurich have been looking for new ways to store large volumes of data over the long term with particular attention being paid to a storage medium found in nature: the genetic material DNA.

The researchers assert that DNA lends itself to this task as it can store large amounts of information in a compact manner. Unfortunately, the data is not always retrievable error-free: gaps and false information in the encoded data arise through chemical degradation and mistakes in DNA sequencing.

However, the team has revealed how the long-term, error-free storage of information can be achieved, potentially for more than a million years.

First, they encapsulate the information-bearing segments of DNA in silica (glass) and second, they use an algorithm in order to correct mistakes in the data.

As encapsulation in silica is roughly comparable to that in fossilized bones, the researchers said they could draw on prehistoric information about the long-term stability of encapsulated DNA and from this calculate a prognosis: through storage in low temperatures, such as that found in the Svalbard Global Seed Vault, which is stored at minus 18 degrees Celsius, DNA-encoded information can survive over a million years. In contrast, data projected on to microfilm can be preserved only for an estimated 500 years.

Wearable electronics for infant MRI patients
In the course of confirming a diagnosis, sometimes even infants must be scanned with an MRI machine. However, the scanning itself can cause physical agitation that interferes with clear imaging. In some cases, it can make it harder for the baby to breathe.

When scans require high sensitivity on a small area of the body, a hard, heavy vest of metal coils must press down on the baby, which weighs more than the baby. Thus, the babies squirm under the pressure, but anesthesia to calm them down adds an unwanted risk. Lightening the load by securing the weighty apparatus off the baby leads to degraded resolution, prompting a need for longer MRI exposures.

The vest is part of the radio frequency (RF) coil assembly that receives the MRI’s electromagnetic signals. Besides being awkward and heavy, the coils are expensive to manufacture and must be reused for years.

With this in mind, MRI experts at UC Berkeley tap colleague Ana Claudia Arias’ lab to come up with a printed electronic solution, which the lab specialized in.

The MRI expert wondered if Arias’s printable electronics techniques could fabricate ultra-lightweight, 2D RF coils to ease the trauma to tiny tots and improve image quality.

New wearable electronics will allow an infant to be swaddled in a blanket laced with a network of nearly weightless, printed “coils” for more comfortable, less expensive MRI scanning. (Source: UC Berkeley)

To make “wearable electronics” for infant MRI patients, her team first tried to print directly onto cloth fabric as they wanted to make the coil feel like a swaddle blanket that fits snugly and softly around the babies, but the cloth’s texture interfered with the ability to print high quality capacitors, so the team turned to printing the “electronic inks” layer by layer onto plastic thin film, like what is used in photo transparencies. The lab succeeded in fabricating and demonstrating functioning RF coils with performance properties comparable to conventional RF coils.

The proof-in-principle of the flexible, lightweight and wearable electronics strategy has led to plans for clinical trials early next year. She and Lustig are collaborating with pediatrician Shreyas The wearable RF coils will be tested at Lucile Packard Children’s hospital on babies needing MRI scans.

The technology could also be adapted for adult MRI scanning as well.

Detecting concussions with a chip
A student startup 8-count at Engineering at Illinois has developed a chip, embedded in helmets or mouthguards, that can detect concussions in athletes right after they suffer collisions.

Their goal was to harness technology to create the first step in helping athletes and coaches respond to concussions. The concept currently works by embedding a chip into the player’s mouthguard, helmet strap or the helmet itself.

The chip analyzes the player’s position and how fast they’re going at the time of an impact, then calculates how hard the player was hit and whether the abuse given was enough to warrant checking for a concussion.

The 8-Count chip and casing. Current versions are small enough to fit into a mouthguard. (Source: ECE Illinois)

Additional reporting by Brian Bailey.