Tag Archives: Jie Shen

‘Nano-hashtags’ for Majorana particles?

The ‘nano-hashtags’ are in fact (assuming a minor leap of imagination) nanowires that resemble hashtags.

Scanning electron microscope image of the device wherein clearly a ‘hashtag’ is formed. Credit: Eindhoven University of Technology

An August 23, 2017 news item on ScienceDaily makes the announcement,

In Nature, an international team of researchers from Eindhoven University of Technology [Netherlands], Delft University of Technology [Netherlands] and the University of California — Santa Barbara presents an advanced quantum chip that will be able to provide definitive proof of the mysterious Majorana particles. These particles, first demonstrated in 2012, are their own antiparticle at one and the same time. The chip, which comprises ultrathin networks of nanowires in the shape of ‘hashtags’, has all the qualities to allow Majorana particles to exchange places. This feature is regarded as the smoking gun for proving their existence and is a crucial step towards their use as a building block for future quantum computers.

An August 23, 2017 Eindhoven University press release (also on EurekAlert), which originated the news item, provides some context and information about the work,

In 2012 it was big news: researchers from Delft University of Technology and Eindhoven University of Technology presented the first experimental signatures for the existence of the Majorana fermion. This particle had been predicted in 1937 by the Italian physicist Ettore Majorana and has the distinctive property of also being its own anti-particle. The Majorana particles emerge at the ends of a semiconductor wire, when in contact with a superconductor material.

Smoking gun

While the discovered particles may have properties typical to Majoranas, the most exciting proof could be obtained by allowing two Majorana particles to exchange places, or ‘braid’ as it is scientifically known. “That’s the smoking gun,” suggests Erik Bakkers, one of the researchers from Eindhoven University of Technology. “The behavior we then see could be the most conclusive evidence yet of Majoranas.”


In the Nature paper that is published today [August 23, 2017], Bakkers and his colleagues present a new device that should be able to show this exchanging of Majoranas. In the original experiment in 2012 two Majorana particles were found in a single wire but they were not able to pass each other without immediately destroying the other. Thus the researchers quite literally had to create space. In the presented experiment they formed intersections using the same kinds of nanowire so that four of these intersections form a ‘hashtag’, #, and thus create a closed circuit along which Majoranas are able to move.

Etch and grow

The researchers built their hashtag device starting from scratch. The nanowires are grown from a specially etched substrate such that they form exactly the desired network which they then expose to a stream of aluminium particles, creating layers of aluminium, a superconductor, on specific spots on the wires – the contacts where the Majorana particles emerge. Places that lie ‘in the shadow’ of other wires stay uncovered.

Leap in quality

The entire process happens in a vacuum and at ultra-cold temperature (around -273 degree Celsius). “This ensures very clean, pure contacts,” says Bakkers, “and enables us to make a considerable leap in the quality of this kind of quantum device.” The measurements demonstrate for a number of electronic and magnetic properties that all the ingredients are present for the Majoranas to braid.

Quantum computers

If the researchers succeed in enabling the Majorana particles to braid, they will at once have killed two birds with one stone. Given their robustness, Majoranas are regarded as the ideal building block for future quantum computers that will be able to perform many calculations simultaneously and thus many times faster than current computers. The braiding of two Majorana particles could form the basis for a qubit, the calculation unit of these computers.

Travel around the world

An interesting detail is that the samples have traveled around the world during the fabrication, combining unique and synergetic activities of each research institution. It started in Delft with patterning and etching the substrate, then to Eindhoven for nanowire growth and to Santa Barbara for aluminium contact formation. Finally back to Delft via Eindhoven for the measurements.

Here’s a link to and a citation for the paper,

Epitaxy of advanced nanowire quantum devices by Sasa Gazibegovic, Diana Car, Hao Zhang, Stijn C. Balk, John A. Logan, Michiel W. A. de Moor, Maja C. Cassidy, Rudi Schmits, Di Xu, Guanzhong Wang, Peter Krogstrup, Roy L. M. Op het Veld, Kun Zuo, Yoram Vos, Jie Shen, Daniël Bouman, Borzoyeh Shojaei, Daniel Pennachio, Joon Sue Lee, Petrus J. van Veldhoven, Sebastian Koelling, Marcel A. Verheijen, Leo P. Kouwenhoven, Chris J. Palmstrøm, & Erik P. A. M. Bakkers. Nature 548, 434–438 (24 August 2017) doi:10.1038/nature23468 Published online 23 August 2017

This paper is behind a paywall.

Dexter Johnson has some additional insight (interview with one of the researchers) in an Aug. 29, 2017 posting on his Nanoclast blog (on the IEEE [institute of Electrical and Electronics Engineers] website).

Oil spill cleanups with supergelators

Researchers in Singapore have proposed a new technology for cleaning up oil spills, according to a June 17, 2016 news item on Nanowerk,

Large-scale oil spills, where hundreds of tons of petroleum products are accidentally released into the oceans, not only have devastating effects on the environment, but have significant socio-economic impact as well [1].

Current techniques of cleaning up oil spills are not very efficient and may even cause further pollution or damage to the environment. These methods, which include the use of toxic detergent-like compounds called dispersants or burning of the oil slick, result in incomplete removal of the oil. The oil molecules remain in the water over long periods and may even be spread over a larger area as they are carried by wind and waves. Further, burning can only be applied to fresh oil slicks of at least 3 millimeters thick, and this process would also cause secondary environmental pollution.

In a bid to improve the technology utilized by cleanup crews to manage and contain such large spills, researchers from the Institute of Bioengineering and Nanotechnology (IBN) of A*STAR [located in Singapore] have invented a smart oil-scavenging material or supergelators that could help clean up oil spills efficiently and rapidly to prevent secondary pollution.

These supergelators are derived from highly soluble small organic molecules, which instantly self-assemble into nanofibers to form a 3D net that traps the oil molecules so that they can be removed easily from the surface of the water.

A June 17, 2016 IBN A*STAR media release, which originated the news item, provides more detail,

“Marine oil spills have a disastrous impact on the environment and marine life, and result in an enormous economic burden on society. Our rapid-acting supergelators offer an effective cleanup solution that can help to contain the severe environmental damage and impact of such incidents in the future,” said IBN Executive Director Professor Jackie Y. Ying.

Motivated by the urgent need for a more effective oil spill control solution, the IBN researchers developed new compounds that dissolve easily in environmentally friendly solvents and gel rapidly upon contact with oil. The supergelator molecules arrange themselves into a 3D network, entangling the oil molecules into clumps that can then be easily skimmed off the water’s surface.

“The most interesting and useful characteristic of our molecules is their ability to stack themselves on top of each other. These stacked columns allow our researchers to create and test different molecular constructions, while finding the best structure that will yield the desired properties,” said IBN Team Leader and Principal Research Scientist Dr Huaqiang Zeng. (Animation: Click to see how the supergelators stack themselves into columns.)

IBN’s supergelators have been tested on various types of weathered and unweathered crude oil in seawater, and have been found to be effective in solidifying all of them. The supergelators take only minutes to solidify the oil at room temperature for easy removal from water. In addition, tests carried out by the research team showed that the supergelator was not toxic to human cells, as well as zebrafish embryos and larvae. The researchers believe that these qualities would make the supergelators suitable for use in large oil spill areas.

The Institute is looking for industrial partners to further develop its technology for commercial use. [emphasis mine]

Video: Click to watch the supergelators in action

  1. The well documented BP Gulf of Mexico oil well accident in 2010 was a catastrophe on an unprecedented scale, with damages amounting to hundreds of billions of dollars. Its wide-ranging effects on the marine ecosystem, as well as the fishing and tourism industries, can still be felt six years on.

Here’s a link to and a citation for the paper,

Instant Room-Temperature Gelation of Crude Oil by Chiral Organogelators by Changliang Ren, Grace Hwee Boon Ng, Hong Wu, Kiat-Hwa Chan, Jie Shen, Cathleen Teh, Jackie Y. Ying, and Huaqiang Zeng. Chem. Mater., 2016, 28 (11), pp 4001–4008 DOI: 10.1021/acs.chemmater.6b01367 Publication Date (Web): May 10, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

I have featured other nanotechnology-enabled oil spill cleanup solutions here. One of the more recent pieces is my Dec. 7, 2015 post about boron nitride sponges. The search terms: ‘oil spill’ and ‘oil spill cleanup’ will help you unearth more.

There have been some promising possibilities and I hope one day these clean up technologies will be brought to market.