World’s smallest pump, with glass electrode 

A team of engineers has created the world’s smallest pump. The minute device, similar in size to a human red blood cell, is powered by an electrode made from something that doesn’t usually conduct electricity - glass.

Applying an electrical current to nanodevices is inherently tricky. Using non-conductive materials makes it even more difficult because they require wires inserted into them, yet they tend to be too small to make the integration of all these moving parts possible. To solve this problem, Alan Hunt from the University of Michigan and his colleagues used a laser to hollow out a bent pipe inside a piece of glass. This resulted in a tiny tunnel with a thin glass wall at one end. Insulating materials such as glass, wood and plastic can conduct electricity at high voltages, but they usually suffer in the process.

“When lightning hits your house, the bolt will pass through your roof, but you end up with a lot of damage,” says Hunt. But a few years ago, his team found that at the nanoscale, ordinary glass becomes conductive without breaking. “When you go down to the nanoscale, the world doesn’t behave as we’re used to,” says Hunt. 

When filled with an electrically conducting solution, the tiny pipe becomes a liquid “wire,” with the glass wall at its tip acting as an electrode. The team has used the electrode to transfer power to an assembly of glass channels that forms the smallest pump ever built, four micrometres across and containing three channels that are 0.6 micrometers wide. The pump can control a flow rate of one-thousandth of one-trillionth of a litre per second. Control over such minuscule volumes could be useful for taking fluid samples from infected cells, or delivering small drug doses to extremely localised sites. Many microfluidic devices are made from glass and other transparent materials, and so are amenable to the new laser technique. Etching electrodes and channels directly into them using the new laser technique could make such devices simpler, says Hsueh-Chia Chang, a specialist in microfluidics at the University of Notre Dame in Indiana.

Janet Fang, Nature News

Sweet sound of music training

Scholars have never agreed on why certain combinations of notes sound sweet while others grate on the ear. A new study shows that the consonance of a musical interval – how pleasant it sounds – may vary based on a listener’s level of music training.  In the study, researchers analysed the musical preferences of more than 250 college students at the University of Minnesota.

There was a strong preference for harmonically related notes, those that are multiples of the same frequency. The appearance of such frequencies is common in Western classical and popular music.

To the researchers’ surprise, the preference for these frequencies also correlated to the length of time a person had played a musical instrument, leading to the idea that how pleasant music sounds may be a learned phenomenon.

“My suspicion is that the whole thing may be learned, but we can’t really conclude that from the data,” said Josh McDermott, the study’s lead author and a researcher at New York University.

Sindya N Bhanoo, NYT News Service