Tag Archives: transformation optics

Light: harvesting with transformation *optics and sensing with a photovoltaic bracelet

There’s a good general description (although it’s still quite technical and challenging) of nanoplasmonics in a Jan. 6, 2014 news release on EurekAlert (later in this posting I have an item about a practical application for photovoltaics),

The control of light is vital to many applications, including imaging, communications, sensing, cancer treatment, and even welding processes for automobile parts. Transformation optics is an emerging field that has revolutionized our understanding of how to control light by constituting an effectively curved electromagnetic space. This revolutionary strategy not only revisits the fundamental physics of light-matter interactions, but also renders trivial the design of optical functions that may otherwise be difficult or virtually impossible, such as an “invisibility cloak,” which could only previously be found in science fiction. When compared with ray optics, the new transformation optics technique provides a picture that is equally intuitive, but that is much more accurate in its description of the wave nature of light by using the electric and magnetic field lines as its basis. Therefore, the validity of this method is not restricted to the macroscopic regime, but can also be extended to the subwavelength scale. In a recent review paper published by SCIENCE CHINA Information Sciences, Yu Luo and colleagues from Imperial College London illustrate how the general capabilities of the transformation optics technique can be used to treat the subwavelength fields that occur in plasmonic systems and review the latest developments in transformation optics as applied to nanophotonics.

Here’s a more detailed description of the difficulties and the solution (transformation optics) from the news release,

In plasmonics, metallic structures with sharp corners can trap light into nanometric volumes, thus giving rise to strong near-field enhancements. This effect can be used to detect single molecules, generate high harmonic signals, and even improve absorption in photovoltaic devices. Further developments using these techniques need to be guided by accurate and versatile theoretical modeling. However, modeling of this type can be difficult, because various aspects associated with the sharp plasmonic structures can hinder provision of accurate and convenient solutions to the problem at hand. First, the size of the sharp metallic point structure is normally much smaller than that of the device overall, which makes it difficult to create meshes for numerical simulations. Second, the strong contrast in the dielectric functions at the metal-dielectric interfaces leads to slow convergence of the field expansions. Yu Luo and colleagues deploy the theory of transformation optics to circumvent these problems. Their idea is to transform a complex plasmonic system with little intrinsic geometrical symmetry into a canonical structure with translational or rotational symmetry, which is then relatively easy to study using conventional theory. For example, two touching nanowires can be transformed into two flat metal surfaces that are separated by a gap, and a sharp metal edge can be related to a periodic array of metal slabs. Other structures that can be studied using transformation optics include pairs of metallic nanospheres, asymmetric core-shell structures and rough metal surfaces. In fact, using transformation optics techniques, we could reverse engineer the optical properties of complex plasmonic nanostructures and redesign these structures based on the requirements of the desired applications.

And then, there’s what seems to be a plea for more researchers in the field,

Practical issues with the realization of plasmonic devices, such as the effects of edge rounding at sharp boundaries on the local field enhancement and resonance properties, can also be considered theoretically using transformation optics and provide useful guidance for the fabrication of these devices. In particular, the necessary conditions are highlighted for both broadband light absorption effects and large field enhancements. Experimental evidence for phenomena that have been predicted by transformation optics has also been reviewed, indicating potential applications in biosensing and broadband solar photovoltaics. These studies demonstrate the accuracy and versatility of transformation optics methods and are expected to encourage more researchers to enter this field. [emphasis mine]

Honestly, I don’t understand nanoplasmonics very well even after reading the description but there’s enough accessible information in the news release to help me achieve a better understanding. For those who want to further explore this latest work in trransformative optics and nanoplasmonics, here’s a link to and a citation for the paper,

Harvesting light with transformation optics by LUO Yu, ZHAO RongKuo, FERNANDEZ-DOMINGUEZ Antonio I., MAIER Stefan A., & PENDRY John B… Sci China Inf Sci, 2013, 56(12): 120401(13).

This paper is open access as of Jan. 8, 2014.

Photovoltaic bracelet/brooch

On to the other ‘light’ topic mentioned earlier. John Brownlee has written about June, a photovoltaic bracelet, which tells you how much sun exposure you’ve had, in a Jan. 7, 2014 article for Fast Company (aka Co-Design; Note: Links have been removed),

… Meet the June, a bedazzling, Bluetooth-connected bracelet that tells you how much sun you’re getting. But don’t dismiss the June just because you’re not worried about the SPF. This is the future of wearables. [emphasis mine]

… fashionably designed wearable that measures exposure to the sun. Made by Netatmo and designed by Louis Vuitton and Harry Winston collaborator Camille Toupet, the June syncs over Bluetooth to a paired iPhone, where an app tells you how much sun you’re getting based upon readings from the bracelet’s photovoltaic gem, and then recommends sunglasses, a hat or a specific sunscreen based upon the measurements. It costs $100,

Lily Hay Newman in a Jan. 8, 2014 posting on Slate’s future tense blog challenges the notion that June is the “future of wearables,”

… it really only does one thing: It measures sun exposure. It’s a single-use device that syncs to a single-use app. Perhaps it foreshadows a world where we each customize our array of wearable sensors by picking and choosing among single-focus gadgets from day to day. Which sensors we want and how we want to look would both play a part in dictating how we dressed and accessorized. Wearables certainly would be a lot more attractive if they weren’t crammed with maximal functionality. But this is also wildly inefficient, and previous technologies haven’t evolved this way. Cameras, MP3 players, calculators, notebooks, calendars, phones, and everything else eventually collapsed into smartphones: one device. No matter how attractive a sensor-turned-bracelet is, there’s a limit to how many wearables one person can actually, you know, wear.

She also notes that June is being marketed to women primarily and suggests that wearables offer an opportunity to change how technology is marketed (Note:Llinks have been removed),

Since the aesthetic direction of wearables is still undetermined, and is currently dictated by the tech inside, the devices present a good opportunity to move away from traditional, often reductive, male and female marketing, which can be particularly blatant in tech. Example: the EPad Femme tablet for women. Alternate example: The Honda Fit She’s. It’s a tall order, but balancing form and function is the crux of the uncertainty in wearables right now.

I recommend reading both articles (Brownlee’s contains a June promotional video). For the curious here’s what the bracelet looks like (from the June webpage),

[downloaded from http://www.netatmo.com/en-US/product/june]

[downloaded from http://www.netatmo.com/en-US/product/june]

June  can also be worn as a brooch; the Netatmo website’s June webpage states,

Versatile, JUNE can be worn as a bracelet or as a brooch.

I haven’t been able to find a product launch date other than it will be ‘sometime in 2014’.

* Removed an extra preposition ‘with’ that preceded the word optics.

Body parts nano style

In early July 2011, there were reports of a new kind of transplant involving a body part made of a biocomposite. Andemariam Teklesenbet Beyene underwent a trachea transplant that required an artificial windpipe crafted by UK experts then flown to Sweden where Beyene’s stem cells were used to coat the windpipe before being transplanted into his body.

It is an extraordinary story not least because Beyene, a patient in a Swedish hospital planning to return to Eritrea after his PhD studies in Iceland, illustrates the international cooperation that made the transplant possible.

The scaffolding material for the artificial windpipe was developed by Professor Alex Seifalian at the University College London in a landmark piece of nanotechnology-enabled tissue engineering. Tim Harper in his July 25, 2011 posting provides more details about the scaffolding,

A team led by Professor Alexander Seifalian (UCL Division of Surgery & Interventional Science; professor of nanotechnology and regenerative medicine at University College London, UK), whose laboratories are headquartered at the Royal Free Hospital, created a glass mold of the patient’s trachea from X-ray computed tomography (CT) scans of the patient. In CT, digital geometry processing is employed to generate a 3D image of the inside of an object from a large series of 2D X-ray images taken around one single axis of rotation.

Then, they manufactured a full size y-shaped trachea scaffold at Professor Seifalian’s laboratories. The scaffold of the trachea was built using a novel nanocomposite polymer developed and patented by Professor Seifalian. Professor Seifalian worked together with Professor Paolo Macchiarini at Karolinska Institutet, Stockholm, Sweden (who also holds an Honorary appointment at UCL).

Professor Seifalian and his team used a porous novel nanocomposite polymer to build the y-shaped trachea scaffold. The pores were millions of little holes, providing this way a place for the patient’s stem cells to grow roots. The team cut strips of the novel nanocomposite polymer and wrapped them around the glass mold creating this way the cartilage rings that conferred structural strength to the trachea.

After the scaffold construct was finished, it was taken to Karolinska Institutet where the patient’s stem cells were seeded by Professor Macchiarini’s team.

Harper goes on to provide more details and insight into what makes this event such an important one.

Meanwhile, Dexter Johnson’s (Nanoclast blog in the IEEE website) July 21, 2011 posting poses a question,

While the nanocomposite scaffold is a critical element to the artificial organ, perhaps no less important was the bioreactor used to grow the stem cells onto it, which was developed at Harvard Bioscience.

If you needed any evidence of how nanotechnology is not only interdisciplinary, but also international, you could just cite this case: UK-developed nanocomposite for the scaffolding material, US-based bioreactor in which the stem cells were grown onto the scaffolding and a Swedish-based medical institute to perform the transplant.

So I ask, which country or region is going to get rich from the breakthrough?

It’s an interesting question and I don’t think I would have framed it in quite that fashion largely because I don’t tend to think of countries or regions getting wealthy from biomedical products since pharmaceutical companies tend to be internationally based. Is Switzerland richer for Novartis?

I suppose I’m a product of the Canadian landscape from which I spring so I think of trees and mines as making a country or region richer as they are inextricably linked to their environment but pharmaceuticals or biomedical appliances can be manufactured anywhere. Consequently, a synthetic organ could be manufactured anywhere once the technology becomes easily available. Who gets rich from this development? I suspect that will be a person or persons if anyone but, not a region or a country.

Getting back to Beyene, here are more details from the July 7, 2011 BBC News article by Michelle Roberts,

Dr Alex Seifalian and his team used this fragile structure [the scaffold] to create a replacement for the patient, whose own windpipe was ravaged by an inoperable tumour.

Despite aggressive chemotherapy and radiotherapy, the cancer had grown to the size of a golf ball and was blocking his breathing. Without a transplant he would have died.

During a 12-hour operation Professor Macchiarini removed all of the tumour and the diseased windpipe and replaced it with the tailor-made replica [now covered with tissue grown from the patient’s bone marrow tricked into growing like cells found in a trachea].

And, importantly, Mr Beyene’s body will accept it as its own, meaning he will not need to take the strong anti-rejection drugs that other transplant patients have to.

Professor Macchiarini said this was the real breakthrough.

“Thanks to nanotechnology, this new branch of regenerative medicine, we are now able to produce a custom-made windpipe within two days or one week.

“This is a synthetic windpipe. The beauty of this is you can have it immediately. There is no delay. This technique does not rely on a human donation.”

He said many other organs could be repaired or replaced in the same way.

A month on from his operation, Mr Beyene is still looking weak, but well.

Sitting up in his hospital bed, he said: “I was very scared, very scared about the operation. But it was live or die.”

My best wishes to Beyene and his family who are also pioneers.

 

A teeny, tiny invisibility cloak and some thoughts about science funding in Canada

Scientists at the University of California (UC) Berkeley have developed a ‘carpet cloak’ which conceals an object underneath it from view. Of course, it’s a very small object measuring 3.8 microns by 400 nanometres. So, don’t get ready for your invisibility cloak yet. If you’re interested there’s a more detailed article, accompanied by a video, here.

There was an essay in the Saturday, May 2, 2009 issue of the Globe and Mail about Canada’s priorities for research and development funding. Written by Harvey Weingarten, president and vice-chancellor at the University of Calgary, the essay made some good points and it made me uneasy. Yes, infrastructure is important and Canadians can get better at commercializing their discoveries so I had no serious disagreement with anything in the essay.

I am, however, uncomfortable with the phrase ‘curiosity-driven’ research to describe research that does not have a commercial application either in the near future or shortly after that. My sense is that the phrase is becoming mildly pejorative. There’s an implication that it’s a waste of time (idle curiousity). To give Weinstein his due, he doesn’t dismiss curiosity-driven research out of hand, he simply drives forward towards his thesis, that Canada needs to learn how to better engage the private sector and to focus its funding efforts on areas where there is already expertise or where it can easily be established. He does mention balance with regard to his aims but I have a suspicion that his notion of balance is different than mine.

It seems like the Gobe and Mail has taken on a campaign to support the sciences. The May 2, 2009 issue had this essay and an extended piece on students pursuing science education and careers or, rather, how students are not pursuing them.

Transformation optics and RockSalt poetry

According to today’s (Oct. 17, 2008) issue of Science, there’s a new field called Transformation Optics. Vladimir M. Shalaev wrote the article which lays out an explanation referencing Einstein’s theory of general relativity where space and time are curved but applying the notion to curving light in arbitrary fashion. Shalaev also discusses some exciting applications including the invisibility cloaks that have been discussed in the blogosphere for the last while. The article titled “Transforming Light” is in the Perspectives section of the magazine. Note: It is behind a paywall. You can find more information about the article and proposed applications here.

The first anthology of BC poetry in 30 years, RockSalt, is being launched with readings from the anthology, which includes over 100 BC poets, on Oct. 23, 2008 at 7 pm at the Agro Cafe (1363 Railspur Alley) on Granville Island . The list of poets who’ll be reading selections on Thurs. (Oct. 23) includes: Heather Haley, Harold Rhenisch, Kate Braid, Mona Fertig, Kuldip Gill, etc.