Thousands of Invisibility Cloaks Trap a Rainbow

Many people anticipating the creation of an invisibility cloak might be surprised to learn that a group of American researchers has created 25,000 individual cloaks.

 But before you rush to buy one from your local shop, the cloaks are just 30 micrometres in diameter and are laid out together on a 25 millimetre gold sheet.

 This array of invisibility cloaks is the first of its kind and has been created by researchers from Towson University and University of Maryland who present their study on May 25, in the Institute of Physics and German Physical Society's New Journal of Physics
 Although the well-reported intention to make everyday objects disappear with a Harry Potter-style cloak is beyond this array of cloaks, they could be used to slow down, or even stop, light, creating what is known as a "trapped rainbow."

 The trapped rainbow could be utilised in tiny biosensors to identify biological materials based on the amount of light they absorb and then subsequently emit, which is known as fluorescence spectroscopy. Slowed-down light has a stronger interaction with molecules than light travelling at normal speeds, so it enables a more detailed analysis.


Lead author of the study, Dr Vera Smolyaninova, said: "The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once. For example, you could test for multiple genetic conditions in a person's DNA in just one go.
"In our array, light is stopped at the boundary of each of the cloaks, meaning we observe the trapped rainbow at the edge of each cloak. This means we could do 'spectroscopy on-a-chip' and examine fluorescence at thousands of points all in one go."
The 25 000 invisibility cloaks are uniformly laid out on a gold sheet, with each having a microlens that bends light around itself, effectively hiding an area in its middle. As the light squeezes through the gaps between each of the cloaks, the different components of light, or colours, are made to stop at ever narrower points, creating the rainbow.
To construct the array of invisibility cloaks, a commercially available microlens array, containing all of the individual microlenses, was coated with a gold film. This was then placed, gold-side down, onto a glass slide which had also been coated with gold, creating a double layer. A laser beam was directed into the array to test performance of the cloaks at different angles.
The researchers believe that this type of array could also be used to test the performance of individual invisibility cloaks, especially in instances where they may be positioned close together. In this study, for example, the cloaks worked very well when light was shone along the rows; however, when it was shone at different angles, imperfections were clearly visible.

New System for Analyzing Information on WikiLeaks, Social Media

The Data Management Group of the Universitat Politècnica de Catalunya (DAMA-UPC) has designed a system for exploring information on networks or graphs that can complement internet search engines and is of particular interest in areas related to social media, the internet, biomedicine, fraud detection, education and advanced bibliographic searches.

According to Josep Lluís Larriba, director of DAMA-UPC, the technology can be used to extract information from WikiLeaks from two perspectives: one, to obtain generic indicators that provide information on whether the data network has the features of a social network and whether communities of data are created that can provide relevant information; and two, to use the documents hosted on the website to analyze how a topic evolves over time, how a person or a group relates to different topics and how the documents themselves interrelate.

High-speed complex queries
The new DEX technology patented by the UPC can be used to explore large volumes of networked data. The system offers high-speed processing, configurable data entry from multiple sources, and the management of networks with billions of nodes and connections from a desktop PC.

Users can quickly and easily identify interrelated records by formulating queries based on simple values such as names and keywords. Until now, this was possible to a certain extent using database technology, but DEX extracts new information from interrelated data and improves the speed and the capacity to perform complex queries in large data networks.

The DAMA-UPC group, which sees huge potential for the technology in the field of social media and the internet, proposes using the DEX system to analyze data on WikiLeaks, the international media organization that publishes anonymous reports and leaked documents on its website.

From fraud detection to the evolution of cancer
In what was the first major application of DEX, the Notary Certification Agency (ANCERT) used the technology to detect fraud in real estate transactions and the Catalan Institute of Oncology is using it to study the evolution of cancer in Catalonia. The DAMA-UPC group is now looking into how DEX technology can be applied to pharmaceutical data analysis to explore developments in the use of medicines.

The group is also conducting research into how information spreads across the internet and at what speed, and why some news spreads faster than others. The project is developed in the framework of the Social Media project, a strategic industrial research project funded by the National Strategic Consortia for Technical Research (CENIT) program.

In the field of e-learning, the team is working on a project under the RecerCaixa grant program aimed at recommending and exploring audiovisual content for primary and secondary schools.

Exploring scientific information
In addition to the fields of health, fraud detection, education and the internet, the technology created by the DAMA-UPC group also offers benefits to the scientific world.

The group has designed BIBEX (www.dama.upc.edu/bibex), a unique prototype for the Spanish Ministry of Science and Innovation aimed at exploring scientific publications and relating specific literature published worldwide. BIBEX also offers other advantages: scientists can recommend scientific articles and find reviewers to evaluate scientific publications. In the future, BIBEX will offer a tool for businesses to find research groups that are working in common areas of interest.

Technology transfer
Sparsity Technologies (www.sparsity-technologies.com) is a spin-off that was created in 2010 with the participation of the UPC to promote and market the technologies developed by the DAMA-UPC group.