All posts by juhi

(An Invisible Title)

Harry Potter Invisibility Cloak

“I am Harry Potter and this is my invisibility cloak! Look – now you see me… and now you don’t!” The eleven year old me gushed as I was getting ready for a night of trick-or-treating.

“It is just a black cloak wrapped around you, I still see you.” That was when I realized that invisibility was only possible in Harry’s magical world.

Or is it?

Recently, I stumbled across an article that claimed that scientists have created an invisibility cloak by using the ‘mirage effect’. Propelled by my childhood dream to possess such a cloak, I began to delve further into this topic. Before we can move into the science behind how such a cloak is made, we need to first understand the concept of refraction, how the human eye perceives objects and how this leads to the mirage effect. Humans are able to see an object because light waves are reflected or refracted (bent) from the object and then travel to the human eye. Sometimes, however, light waves from an object pass through another medium and bend the light wave another direction. Imagine, for instance, a spoon inside a glass of water – when inside a glass of water, the spoon appears to be ‘broken’. This is because the light waves reflected from the part of the spoon submerged under water, are refracted when they pass through the surface of water. Unfortunately, our brain does not know the light waves from the spoon have been refracted, and thus we perceive the spoon to be at different position under water. Figure 1 below further explains this concept.

Concept of Refraction

Figure 1: Concept of Refraction

The mirage effect is based off this concept. Many of you must have probably experienced driving down a road on a hot summer day and seeing a pool of water in the distance, only to realize that it was actually a mirage. Mirages form because of a temperature gradient between the air and surface of the ground. Usually, light waves from the blue sky are reflected off the surface of a road and thus allow us to see the road ahead. However, in a mirage, a very hot surface causes the light waves from the sky to refract before coming in contact with the road. Since our brain does not know the light wave has been bent, the eye traces the light wave in a straight line to the ground, thus causing our eyes to incorrectly perceive the light waves as a pool of water in the distance (when it is actually refracted light waves from the sky).

Using the concept of the mirage effect, scientists have made an invisibility cloak out of a lattice of carbon nanotubes that when electrically stimulated, either by electrical heating or by a pulse of electromagnetic radiation, create a temperature gradient that cause light waves to bend away from whatever object is under the invisibility cloak. The most important aspect of such an invisibility cloak is the lattice of carbon nanotubes. In order to bend visible light waves, the lattice of carbon nanotubes (also known as metamaterial) must be spaced less than the wavelength of visible light. Till now, researchers have only been able to succeed with near-infrared radiation as our technology is not sophisticated enough as yet to create a lattice with smaller spaces between the carbon nanotubes. Thus, until scientists are able to create a lattice small enough to bend light waves from the visible spectrum, an object will remain visible to the human eye.

Refraction of Light Waves to make Object Invisible

Figure 2: An object covered in an invisibility cloak made of carbon nanotubes that bend the light waves around the object, making the object invisible.

So what does all this really mean? Could Harry Potter’s invisibility cloak really exist? In the future, perhaps yes. Yet, there are even bigger implications of a possible invisibility cloak – good and bad. Using metamaterials to bend light waves, society could improve its security by placing ‘invisible’ policemen around each city. A country’s military could also benefit from such technology as tanks and airbases could be hidden from the human eye. However, such an invisibility cloak could also increase crime rate in the future as this technology could be further developed to bend sound and magnetic waves as well, allowing terrorists carrying guns or bombs to walk through metal detectors undetected. This could arouse an ethical debate over the use of metamaterials and invisibility cloaks. Yet, the debate can wait till the day researchers create the first cloak invisible to the human eye.

Bibliography:

1. “HowStuffWorks “Metamaterials: Bending Light Waves”” HowStuffWorks “Science”Web. 07 Oct. 2011. <http://science.howstuffworks.com/invisibility-cloak6.htm>.

2. “Researchers Create Functional Invisibility Cloak Using ‘Mirage Effect’ | Fox News.” Fox News – Breaking News Updates | Latest News Headlines | Photos & News Videos. Web. 07 Oct. 2011. <http://www.foxnews.com/scitech/2011/10/05/researchers-create-functional-invisibility-cloak-using-mirage-effect/>.

3. “How Do ‘invisibility Cloaks’ Work?| Explore | Physics.org.” Physics.org | Home. Web. 07 Oct. 2011. <http://www.physics.org/article-questions.asp?id=69>.

A Wall of Water

March 11, 2011. Breaking News: Japan’s most powerful earthquake since records began has struck the north-east coast, triggering a massive tsunami. In the family room, we watched in silence as the footage of the giant debris-filled wall of water making its way inland was replayed over and over again. As the reporter recounted the details of this earthquake with an intensity of 9.0 on the Richter scale, my mind drifted towards the science behind the formation of these giant havoc-wreaking monsters that have frequently caused heart-breaking destruction and loss of life. More importantly, how do earthquakes lead to these deadly 10meter tall tsunamis?

Before we understand how tsunamis are formed, it is important to understand that the Earth’s crust is not one giant spherical unbroken land mass. Rather, it is made up of jigsaw puzzle like pieces called tectonic plates. These plates move approximately 2 inches a year because of the movement of heat carried from the inner core to the Earth’s crust; however, sometimes the plates move abruptly (as the regular movement is restricted by friction), causing an earthquake.

“But not all earthquakes are the same. It depends on whether the relative movement between the plates is horizontal or vertical.” In addition, the location of an earthquake could be on land, or under the ocean floor. Tsunamis are only formed when the relative movement of the tectonic plates is vertical and under the ocean floor. When the plates move vertically under water, the movement (“thrust”) produces a large displacement of water from its equilibrium position that needs to somehow regain its equilibrium as the gained potential energy converts to kinetic energy in the form of a fast-moving wall of water.

“The water has to go somewhere,” explains Dr Wayne Richardson of the International Seismological Centre, “and it has to go at once. It’s not like a wave breaking at the beach. It’s a mass movement. It can travel, depending on the depth of the water, at up to 950 kilometres per hour (589mph) in the deep ocean.”

As the topography of the sea floor changes and the wave approaches shallow water, the speed slows down and the height of the wave increases (as illustrated in diagram below).

How Tsunamis are Formed

Yet, it is important to note that not every single underwater earthquake will form a tsunami – the magnitude of an earthquake, measured by the Richter’s Scale, must be taken into consideration. Scientific research has proven that usually earthquakes 7.0 and below do not result in tsunamis, and if they do, they rarely lead to massive destruction.

Tsunamis are natural disasters, and they cannot be prevented. It is, therefore, our responsibility to be adequately prepared for this natural calamity.

Due to the fact that Tsunamis have a small amplitude and a long wavelength (up to hundreds of miles) offshore, they can frequently pass unnoticed until they reach shallow water, and therefore it is very important for tsunami-prone nations to install adequate and accurate tsunami sensing and early warning technology. This can be a challenge for poor, underdeveloped nations and I believe that they should be supported by developed nations.

It is also important for the governments of tsunami-prone nations to make wise decisions when building infrastructure offshore/close to shore that could have catastrophic and life-threatening consequences if hit by a tsunami e.g: nuclear power plants, offshore drilling rigs, etc. (as seen in the recent nuclear plant meltdown in Japan)

Last but not the least, it is important that a communication system is in place that allows tsunami warnings to reach every individual in the risk region and an evacuation policy that allows all to be evacuated in due time.

Bibliography:

“Earth Plate Tectonics.” Windows to the Universe. Web. 15 Mar. 2011. <http://www.windows2universe.org/earth/interior/plate_tectonics.html>.

News, Roland Buerk BBC. “BBC News – Japan Earthquake: Tsunami Hits North-east.” BBC – Homepage. Web. 15 Mar. 2011. <http://www.bbc.co.uk/news/world-asia-pacific-12709598>.

Melina, Remy. “Why Do Some Earthquakes Cause Tsunamis But Others Don’t? | Earthquakes & Tsunamis | Life’s Little Mysteries.” Life’s Little Mysteries – A Daily Investigation of the World Around You. Web. 15 Mar. 2011. <http://www.lifeslittlemysteries.com/why-do-some-earthquakes-cause-tsunamis-but-others-dont-1125/>.

“Tsunami Science: a Wall of Water.” Tsunami Science: a Wall of Water. Channel 4 News, 11 Mar. 2011. Web. 15 Mar. 2011. <http://www.channel4.com/news/tsunami-science-a-wall-of-water>.

Stain-repellent Khakis??

Ever strolled into an outfit store and picked out a pair of khaki trousers from a rack that has a big red poster hanging from it with three simple words printed on it: “Stain-Repellent Fabric”? And you go thinking, “Yeah right!”

All of us have gone through the unpleasant experience of dropping drinks and foods on our clothes before and watching in distress at the giant stain that appears soon after. So, how can fabric be stain-repellent? It must simply be a marketing stunt? Incorrect. Welcome to the realm of nanotechnology.

On a basic level, nanotechnology is the manipulation of molecules in order to build structures starting from the molecular state. When working with nanotechnology, scientists work with structures from 1 nanometer to 100 nanometers. In order to understand how small that actually is, you can see below that a red blood cell is approximately 7000 nanometers across.The size of a red blood cell

Now, imagine working with particles seven hundred to seven THOUSAND times smaller – and we all have trouble putting a thread through the eye of a needle!

So how does the concept of nanotechnology have anything to do with stain-repellent fabrics? Working with structures so small allows textile manufacturers like Nano-Tex, to work with nano-sized particles and fibers that further enhance the quality of the fabrics. By using nano-sized fibers, also known as nanowhiskers, these manufacturers are able “to pack extra atoms” into the fabric atoms, which help repel liquids spilt on the surface of the fabrics.  Thus, the fabric is almost invulnerable to liquid as the tightly packed atoms cause the liquid to bead up and slide off the fabric rather than soak into the fabric.

Kool Aid beads up on Fabric

In this picture, red kool-aid is poured onto a pair of trousers and you can see that instead of soaking up into the fabric, the liquid is beading up.

Nanowhisker embedded in fabric

In order to embed the nanowhiskers into the fabric, as shown in the picture, the fabric is submerged into water filled with billions of nanowhiskers. As the water is heated and evaporated, the nanowhiskers bond chemically with the fabric. The nanowhiskers make the fabric hydrophobic, i.e. water-hating. Therefore, the implanting of nanowhiskers prevents the water from soaking into the fabric, and instead they act like “the fuzz on a kiwi” and create a cushion of air around the fabric, causing the liquid to bead up (due to surface tension of the liquid droplet) and roll off. Unfortunately, the chemical makeup of nanowhiskers is unavailable in the public domain and thus, it is not possible to demonstrate the bonding of cotton fabric (cellulose) to nanowhiskers.

So, it turns out that “stain-repellent” clothes are not just a marketing gimmick, but rather cutting-edge technology. However, nanotechnology is not limited to consumer-based products only. Research is ongoing in the field of medicine to produce delivery systems that can pinpoint and destroy viruses and cancers with laser-like accuracy rather than the collateral damage of chemotherapy today. In addition, work is ongoing to produce light-weight carbon materials many hundred times stronger than steel among other applications.

As nanotechnology advances, there are several unanswered questions. What is nanotechnology: 1nm to 100nm or just up to two-tenths of a nanometer? How long will it take before nanotechnology is useful from the mainstream perspective? Are we aware of all the possible deleterious effects of nanotechnology (stain-repellent fabrics), and are there any regulations to protect us from the same? One of the areas of research is increasing the human lifespan – will this be available to all or a prerogative of the rich only?

598 words.

Bibliography:

1. ” Introduction to Nanotechnology.” Nanotechnology Made Clear. Web. 17 Oct. 2010.

<http://www.understandingnano.com/introduction.html>.

2. “Nano-particles & Their Uses in Textiles | Processing, Dyeing & Finishing | Features | The

ITJ.” The Indian Textile Journal – Technology & Trade Info for Tomorrow’s Textile

Industry. Web. 17 Oct. 2010.

<http://www.indiantextilejournal.com/articles/FAdetails.asp?id=693>.

3.  NanoSense. Web. 17 Oct. 2010. <http://nanosense.org/>.

4. Home. Web. 17 Oct. 2010. <http://www.bekaerttextiles.com/>.