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Engineering At The Nanoscale April 14, 2012

Posted by peterxu422 in Science, Technology.
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Devices keep getting smaller. Objects that once were only seen with the naked eye now can be looked at through a microscope. How do we keep putting more stuff in less space?

Building technology at the nanoscale, virtually at the atomic level, is the heart of our modern day technological revolution. It seems impossible that engineers can perform such a feat. How do they do it? It turns out some of the techniques used to fabricate at the nanoscale are not as Herculean as one might imagine.

Currently, I work in Dr. Vinod Menon’s Laboratory for Nano and Micro Photonics (LaNMP) at Queens College. The work I do there regularly involves creating structures with very fine thicknesses. For example, I often need to place a layer of material about 400 nm thick on top of a glass piece. The technique I use to accomplish this is called spin coating. There is a device called a spin coater which consists of a rotating platform. I place my glass slide on top of the platform, and use suction to keep it fixed on the mount. I take a liquid solution of my material and place a few drops on top of the glass. The spin coater allows me to adjust the spin speed and spin time. When I let it run, the platform begins to spin rapidly. Because of the centrifugal force caused by the rotation, a lot of the solution flings off the glass slide leaving only a very thin but even layer of material on top of my glass slide that is only nanometers thick. The faster it spins, the thinner it gets. The longer it spins, the thinner it gets.

This week, I went to City College to use one of their devices that allowed me to deposit thin layers of gold on top of a piece of Silicon. The device had an airtight chamber where I placed my samples inside as well as the gold I would be depositing. The gold was held between two metallic fixtures that kept it in place, and the Silicon pieces were laid underneath. The air is sucked out of the chamber to remove any impurities in the process. Because the gold piece is held between two metallic fixtures, I can pass a current through it which would heat up the gold and cause it to vaporize. I raise the current to 50 Amps and the gold piece begins to glow hot. A detector inside displays a reading of how thick the gold layer is and I see that the reading is increasing.

Intel, the largest semiconductor chip making company in the world, also uses special techniques to create their ever increasingly powerful chips. They use a technique called photolithography to fabricate their chips. The way it works is they usually have a base material called a substrate. Then they put a layer of semiconducting material on top of the substrate. This material is sensitive to light, meaning when light is shined on it, it vaporizes. They then put on top of this layer a stencil, that outlines the pattern they want to draw on their chip. Once the stencil is in place, they use light, usually ultraviolet light, to blast away the exposed layers. The parts that are covered by the stencil are kept intact and thus they produce a desired pattern on their chip. They repeat this process with other material as well until they have their completed structure.

There are a number of other techniques that can be used to engineer at the nanoscale. The ones I have mentioned are those that I have been exposed to and had personal experience with. As you can see, building nanoscale structures does not have to involve a very intricate and complicated process. We can use accessible macroscopic techniques to achieve microscopic creations.

Revisiting the Periodic Table April 8, 2012

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This week on the PBS show NOVA, David Pogue, a New York Times tech columnist, hosted a two hour program titled “Hunting The Elements”. Being the funny goofy person that he is, he made the episode very entertaining filled with fascinating science explained. It is definitely worth a watch for those who have Periodic Table phobia, a term I coined describing those who fear or dislike looking at a periodic table because they do not know how to read one. This program would be great medicine for that.

In the episode, he talks about the reactivity of elements, their origins, their uses, and their properties. In one scene, he goes to an explosion range where he and the fellow scientists test out the explosion speeds of different types of explosive materials like gunpowder, nitrate gel, and C4. He explains that how fast a substance explodes depends on how far away oxygen atoms are from each other within the molecules. Things that burn require oxygen, and so if oxygen is closer to the exploding substance, the reaction can occur more quickly and thus the explosion will be faster. Gunpowder was the slowest one because it has oxygen atoms far away. This is why it’s used to fire projectiles because it has enough force to shoot a projectile out but not enough to destroy the barrel of the gun. C4 is the fastest because the molecules that make up C4 have the oxygen atoms packed closely together.

In another sequence, he visits a bell manufacturing company and makes a whole bronze bell with them. He explains that bronze is made from a combination of copper and tin. Copper is malleable. So if a bell was made of copper and it was struck, it would not create a very good sound since the denting would absorb some of the mechanical energy that would have caused the vibrations to create the sound. Adding tin to the mixture fills up some of the gaps between the copper atoms which would restrict their movement. You get a much sturdier material which is very good for making the resonating rings of bells. Pogue then took a sample of the bell’s material to a lab to see if they had a good mixture of tin and copper. At the lab, they used an electron microscope and magnified the sample to such incredible scales that they were looking at the actual atoms themselves. It showed a very ordered layer of dots where the brighter ones were tin atoms while the darker ones were copper.


Electron microscope image of diamond and silicon

The last sequence I’d like to mention was about shark repellent material. Apparently, the lonely bottom two layers of the Periodic Table, the rare earth metals, have some purpose. These elements are supposedly able to repel sharks. The man who demonstrated this made a large powerful magnet out of one type of rare earth element and when he brought it close to a shark, it immediately turned its head away. They do a few other experiments that clearly illustrate the sharks do not like this material. They suspect the reason for this is that the sharks feel an electric shock when in the presence of this material. When they placed the magnet and a shark fin into a beaker of water, and connected two electric wires from a Voltmeter to it, they showed that a current was flowing. The atoms flowing off the magnet would lose their electrons making them positively charged. These positive ions are then attracted to the shark fin and they flow along it. This stream of moving charges creates a current thus giving a small jolt to the shark. However, the problem I see is that this explanation assumes that the magnet is inside the water. But when they brought the magnet close to the shark form the outer wall of the pool, the shark showed the same reaction. There must be more to the story than the explanation of the electric current.

Finally, to further your experience with the periodic table, I recommend downloading the free iPad app inspired by this program called The Elements. Pogue helped design it himself. It has an interactive Periodic Table, a fun molecule building game, and the whole Hunting the Elements program on it. David Pogue will be replacing Neil deGrasse Tyson as host of NOVA Science Now for the time-being. Dr. Tyson is taking time to film a reboot series of “Cosmos” formerly hosted by Carl Sagan. Pogue is an excellent choice for a host. I had the privilege of meeting him once and he is a very kind and funny person.

VIDEO: Preview for Hunting the Elements

Warp Speed March 25, 2012

Posted by peterxu422 in astrophysics, cosmos, Science, Technology.
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Even if you are not a card-carrying sci-fi fan, you may have at some point encountered the term warp speed and perhaps even contemplated about its realities. While inter-galatctic travel and teleportation are still a far reach technologically, theoretically, that is within the known laws of physics, they are not in violation with our understanding of nature.

Warp speed, if you are not familiar, is traveling through space much faster than the speed of light. According to Einstein’s theory of Special Relativity, the fundamental speed limit in the universe is the speed of light, 300 million meters per second. Sounds fast right? But let’s put that number in perspective. If you were to travel at the speed of light from Earth to the center of the Milky Way, it would take you 25,000 years to get there. Forget about going to another galaxy within a reasonable time period. Also from relativity, due to a phenomenon known as length contraction, we know that objects get contracted as they get faster and faster. If an object travels at the speed of light, it will ultimately become contracted and squeezed into nothingness. Not very convenient for space travel either.

But if the speed of light is the ultimate speed limit, how do we get around this problem? The potential solution lies in Einstein’s theory of General Relativity, which tells us how space is curved and can be warped. The one thing that can move faster than light is how fast space itself stretches. We know this because during the Big Bang, space expanded faster than the speed of light. Thus, to travel between two distant points in space, we can manipulate space itself to get to our destination.

The way to do this would be to expand the space behind you and compress it in front of you. The expansion of the space behind you gives the appearance of a push while the compressing space in front of you is dragging you forward. But realize that this does not violate Einstein’s postulate that nothing can travel faster than the speed of light. You yourself are not moving, but space is and it can move as fast as it wants.

The best way to imagine this is by taking a balloon, where the surface of the balloon represents space. Suppose you draw two dots A and B. You are at A but B is located very far away. Now imagine taking a cut-out spaceship and taping it to a ribbon that can wrap around the balloon so that the ribbon is tied around the balloon, but not bound to it. If you squeeze the portion of the balloon in front of the spaceship, “space” is being compressed. But you’ll also notice that point A got farther away from the spaceship and point B got closer. From your perspective, the spaceship did not actually move, space did.

How then do we actually go about warping space? Well, it’s not easy, and certainly requires technology beyond anything humanity possesses currently. But in theory, a way to accomplish this is by using a HUGE amount of energy, specifically negative energy. Negative energy has an opposite effect on things. For example, if something were about to collapse in on itself, negative energy would hold it outward. If something falls down, negative energy would make it float up. A combination of negative and positive energy pushing and pulling on the space around the spacecraft would give the desired warping effect of space. So a spaceship with warp drive capabilities would have on it an engine that could create something like a bubble of this negative and positive energy enveloping the vessel.

Also, as you may have seen in sci-fi flicks that when spaceships go into warp drive, the light from point sources in space begin to stretch and get all line-y. The reason it is rendered this way is because as the spaceship moves faster, it is catching up in speed to these light beams and so the crew on-board sees how the light actually looks in its beam form. But remember, the ship itself isn’t moving faster, the space around it is.

VIDEO: World Science Festival Warp Drive, Lawrence Krauss

Star Trek 2009 Warp

Analog & Digital Signals February 25, 2012

Posted by peterxu422 in Science, Technology.
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For as long as I can remember, I have heard the terms Analog and Digital signals. In this advanced digital era, the terms have become more ubiquitous than ever. Though I was familiar with their names, I have never quite understood what they actually were or their differences until recently.


An analog signal is a continuous signal that varies with time. Continuous simply means that it is not interrupted. For example, a traditional clock with hands is an analog source. The hands keep moving without interruption and so it shows you EVERY moment of time during the day. A digital signal on the other hand only shows you finite quantities that change with time. A digital clock is, obviously, a digital source. Most only display up to the minutes. As a result, the time does not change continuously, but in steps of minutes. A digital clock that changes from 10:00 to 10:01 only shows you a change in the minute. But what about the seconds in between, or the milliseconds in between, or the nanoseconds in between? An analog clock on the other hand, technically shows you all of these and more, even though our human eyes are unable to detect them.

Another example of an analog signal would be that produced by a microphone. When you speak, your vocal chords cause the surrounding air molecules to vibrate which produce sound. If you hold a microphone close to you and speak into it, the vibration of the air molecules causes a metallic coil inside the microphone to vibrate accordingly. When the coil vibrates, it creates an electrical current that resembles the sound. The current is a continuous varying signal and so it is an analog signal. In technical terms, the current becomes an analog of the sound. This current is then fed to an amplifier and reconverted back into vibration which produces a louder sound.

What has puzzled me most about analog and digital signals is how they can be converted back and forth. Digital signals as we all know are composed of units of information called bits, which are represented by 0’s and 1’s. How then, I wondered, could a simple set of 0’s and 1’s represent something as complicated as a sound signal?

The way it works is as follows. Most analog signals can be converted to electrical currents. These electrical currents change with time and their “strength,” or amplitude, constantly changes as well. If you divide up the signal into sections, at certain points, the current will have a certain amplitude. At one instant it might be 7 Amps, then later on the signal could decrease and become 2 Amps. These values can be represented as binary numbers (number consisting only of 0’s and 1’s). If you do this for many amplitudes, you can essentially represent the entire analog signal in binary. This is the conversion from analog to digital.

In the end, the digital signal needs to be converted back to analog to get the original signal back (remember the microphone?). So you may ask what’s the point of this anyway? Well, the benefit of digital is that it is very useful for transporting data. Analog signals are constantly changing and controlling their amplitudes is difficult. Also, transporting them over long distances makes it more susceptible to signal degradation and quality loss. But with digital, you only need to control two values, 0 and 1, which is basically a no pulse or pulse of current. Since it uses just these two values and nothing in between, it makes it less likely for the signal to degrade. If a pulse of current is sent (1) and during its transport it slightly decreases and becomes say 0.80, on the receiving end it gets rounded to the closest value and becomes a 1 again, thus preserving the signal. This is the reason why digital signals are of such clear and high quality.

My First Hackathon October 14, 2011

Posted by peterxu422 in Business, Entrepreneurship, Science, Technology.
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About a week ago, I attended my first hackathon hosted by the non-profit organization hackNY. What is a hackathon? It is an event where a bunch of programmers come together and build something within a certain amount of time. How long do they last? This one was 24 hours, others can last up to an entire week. What do they build? Programs, applications, web apps, perhaps even more. The rules of this hackathon was to build something awesome within 24 hours.

The day-long event began at 2pm on a Saturday and ended 2pm Sunday. A variety of delicious foods was served regularly throughout the entire night to keep the hackers energized and awake. Lots of Redbull and Monster energy drinks too.

After the hackers registered and signed in, we sat in the auditorium waiting for representatives from various web startup companies in NYC present their API’s. The API is basically documentation that teaches you how to use a company’s software in your own applications. So for example, if I wanted to build an application that would allow me to input an address which would then output the location on a Google Map and present pictures of the nearby area on a Panoramio Widget, I would use the Google Maps API and the Panoramio API to see how I could incorporate their services into my program. This is basically what I, along with a few others, built that night.

To say the least, my experience there showed me how challenging developing web applications can be. It is quite different from the non-web programming I have done in Java and C++. My brief background in computer science allowed me to write and interpret code, but as far as actually creating a web application was quite challenging and unfamiliar. I actually felt quite demoralized by this, as I realized how inept my software development skills were. This was particularly demoralizing given my desire is to be a tech innovator.

However, I was fortunate enough to meet people there who were at my level, and even more fortunate to meet experienced coders willing to help us get started. After the hackathon event, we maintained communication with each other and expressed an interest in continuing to learn how to do web development. We are currently working on a collaborative project outside of school. It will be fast paced and will likely take a chunk of my time, but I think the experience will be worth it.

Part of my new resolution was to take more risks. Taking on this project bears some risks, particularly to my academics, but what great opportunity does not involve taking risks? The late Steve Jobs has shown us that the things you build can change the world. Sometimes, you have to stop studying how something works, and actually make it. Let’s start building.

Hackers at the hackathon

The Maker Faire September 24, 2011

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Exactly last week, I attended the Maker Faire in the New York Hall of Science in Queens. The Maker Faire is essentially a large gathering of hobbyists, technologists, developers, creators, inventors, and some big name companies and organizations. It is a fair, so there were exhibits and pavilions set up for the different groups that were being represented. Some of those who were there included Radio Shack, Arduino, MIT Research Labs, City College CUNY, NYU Poly, Engineering World Health, and so many more.

It was a terrific event. Highly recommended especially for youth. There were lots of demos and free activities for kids and adults to really work with their hands. I spent most of my time doing soldering work. Soldering is taking a particular type of metal and melting it onto electronics circuits to both attach components as well as provide a electrically conductive channel between the chip and the component.
Have you ever seen electrical engineers carrying a pen-like object when working with circuits? That’s a very hot device called a soldering iron. Its tip is heated to roughly 750 degrees Celsius and has the capacity to melt a particular type of metal called solder upon contact. Solder is made of Tin and Lead. It melts quickly and conducts well.

I visited a few exhibits that allowed me to solder. I built a small LED clip, a small flashlight, and an Electrical Surgical Unit (ESU) Tester. The ESU project was with the non-profit organization Engineering World Health. What they had was a small kit that consisted of parts. When these were soldered together, they would form a testing unit for electrical surgical pens, which use current to cut open patients rather than a blade. The ESU tested the power of the current. I spent about an hour soldering it all together, and it was major fun. I got a free t-shirt from them for helping them out, because they send these units to third world countries to use. Here is my final product:

Some other highlights there included: A wand controlled robot powered by Arduino

KeyGlove, a keyboard-free alternative to typing, also powered by Arduino

A 3-D Printer, prints real objects!

And Sifted, a new way of thinking about gaming

Perhaps the biggest highlight of my Maker Faire trip was listening to and meeting David Pogue, popular tech columnist for the New York Times and host of the NOVA series “Making Stuff” (See ‘links’ page to get to NOVA’s homepage). His talk was titled the “iPhone Brain Dump,” which he basically talked about some wonderful features of the iPhone. Some of the apps he highlighted included Ocarino, which is a flute-like instrument that can be played by blowing into the microphone of the iPhone. What’s great is that you can listen to anyone else in the world playing with the App. All in all, David Pogue’s talk was wonderful and speaking to him afterwards was incredible too.

The Maker Faire was an incredible event filled with creativity, inspiration, ingenuity, and innovation. Brilliant people with incredible projects gather together to celebrate the act of building something awesome. How great is that?

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