Tag: materials

This Tiny Sponge is Probably Set to Change The World

By Anupum Pant

Background

Things absorbing water from the air is nothing new. Hygroscopic substances – or substances which have ability to attract and hold water molecules from the surrounding environment – have always been around. Coffee powder for instance is one great example – leave the dry coffee powder in the open and it will turn into a mushy matter within hours. Thanks to the moisture present in the air that it absorbs.

Hygroscopy in Nature

In the nature too, hygroscopy – the ability to extract water from thin air – has some peculiar functions. One fantastic example is the seed of the needle-and-Thread grass. This seed, with the help of a hygroscopic awn attached to it, can twist and untwist the screw like structure by releasing and absorbing moisture from the air. This way, it is able to dig its way into the ground. But that’s just one of the many examples of how hygroscopy is all around us. Here’s another one…

Thorny devil – an Australian lizard – lives in the arid scrubland and desert that covers most of central Australia. It has a hard time finding water in this dry place. So, blessed by the evolutionary forces of nature, the lizard has developed tiny hygroscopic channels between the spines on its back. These channels, working in tandem with a capillary action mechanism, are able to draw water from the air. Then their precise design makes the water move into the mouth of the lizard. Fascinating!

Other Ways

Although not exactly using hygroscopy, the Namib desert beetle, also does something similar – drawing water from thin air. Unlike the hygroscopic grooves of the thorny devil’s back, the desert dwelling beetle has developed some patterns on its hard wings which help it in drawing water from the air. These patterns include an array of  hydrophobic and hydrophilic materials which are able to trap water from the foggy morning air and are able to channel it to the beetle’s mouth.

The Nanotube Sponge Mat

This particular beetle’s hard wings with magical patterns on it, intrigued a couple of researchers. They took cue from this natural material and were able to create an artificial mat which could absorb water from the air.

nanotube sponge

Although we do have commercial Atmospheric Water Generators (AWG) which can harvest water from the air and supply drinking water, the sad thing is that these things run on electricity. This new mat that was fabricated recently, using an array of carbon nano tubes sandwiched between hydrophilic and hydrophobic layers, doesn’t need any electricity to extract water.

This mat they’ve fabricated is smaller than your thumbnail, but it still works, and is able to extract about 1/4th of it’s weigh in water within a few hours. The researchers are working on it to make it more efficient. [more information] [Original Paper]

A couple of years back a US based startup, NBD Nano, was inclined on developing a water bottle based on the same Namib desert beetle principle. The much touted water bottle, they said, would be able to fill itself! I’m not sure where their project is headed today, but an auto-filling water bottle sure would be a product just too cool to not own by every kid at school!

Needless to say, it would probably make a huge difference by lowering greatly the number of people who don’t find clean drinking water every day – Just for the record, about 1/7th of the world population didn’t have access to clean water today.

Revolutionary – A Simple Yet Much Stronger Artificial Muscle

By Anupum Pant

Background

Some things are just too simple to be noticed by most adults, rather a child would notice it better. Scientists are the ones who manage to hone their ability to  look at things like a child would see it – Children of course are the best scientists. That is what makes scientists different from most other people. And that is what helps them make elegant discoveries, like the one we are seeing here today.

Now, this may seem like a useless thing to some, but in reality the simple fishing line muscle is a huge step towards creating affordable personal robots, exoskeletons and a host of other earth changing devices. I can’t stop thinking how massive this simple thing could end up being.

The Discovery

A team of researchers at the University of Texas at Dallas, did exactly that. In a simple nylon fishing line, these researchers saw something that everyone till date has failed to notice. They noticed that, by twisting a nylon line into a coil (and heat treating), they could turn it into an artificial muscle. Later it was learnt that a simple artificial muscle made in this manner is about 100 times stronger than a human muscle and can go through millions of cycles without failing.

It’s actually so simple to do that you could make an artificial muscle in your own home. In fact, it works with a variety of other kinds of materials too, but better stick to the tested fishing line for now.

All you need to do is to hold one end of a long fishing line and start twisting the other end (a hand mixer could come in handy here). At some point the line reaches a point where it can’t twist any more, and then it starts getting coiled into a telephone wire kind of a spring. Now it can be heated in an oven (carefully, without melting) and cooled to lock it in this coil shape. There, you’ve got your own artificial muscle.

Working

Unlike what you think it would do when heated, the coil actually contracts and can lift a good amount of weight. An array of such artificial muscle fibres could lift a much heavier weight. as shown in the video below.

At first I found it confusing. It was hard for me to understand, what physics goes inside that makes the coil contract as a whole when it is heated. From the words of a wise scienitist, I found that it works like a chinese finger trap (and then I had to look what this piece of origami was). Whatever the coil does is absolutely elegant. It’s almost impossible for me to explain in words how it works. You might have to watch the video below…

The catch is that the nylon muscles made in this manner are very inefficient, but that can be worked upon.

Lycurgus Cup – An Ancient Nanotech Marvel

By Anupum Pant

The concepts of modern nanotechnology must have been first seeded in the year 1959 by the renowned physicist Richard Feynman, but Romans were already doing it back in 300 AD (around 290-325 AD). About 1700 years back, utilizing the principles of Nanotechnology, Roman engineers had crafted a magnificent chalice – Lycurgus Cup (picture). Like the Prince Rupert’s drop, this is another glass marvel you should know about.

Side note: You can listen to the legendary lecture by Dr. Feynman on YouTube – There’s Plenty of Room at the Bottom, where he discusses the “possibility of synthesis via direct manipulation of atoms”, or Nanotechnology.

Lycurgus cup description

The Lycurgus cup was probably the first ever optical artificial [meta]material – Ruby Glass – engineered to have properties that may not be found in nature. Its unusual optical properties are something that makes it stand out.

Normally, the cup appears green, but if it is illuminated from the inside or lit up using a light placed behind it, it glows ruby-red; hence the name, ruby glass. This kind of glass is known as a Dichroic glass. Dichroic  literally means ”two colored” and is derived from the Greek words ”di” for two, and ”chroma” for color; in this case, the colors green and red.

The technology behind this cup baffled scientists for around 40 years (from 1950s to 1990s). It was only in 1990s that they figured out how it really worked. The goblet has been preserved well, and is presently at display in the British Museum.

Dichroic glass

Dichroic glasses do not use paints, dyes, or any coloring agents for the color. They are made using fine coatings on glass. The coatings themselves do not have a color, but rather they bend light to reflect colors like a prism does, to make rainbows.

These colors are visible due to the presence of very minute amounts of finely ground gold and silver particles in it. Romans could have included these powders unknowingly as contaminants or might have added them on purpose to achieve the very effect, we’ll never know.

Inspired by an age-old technology

NASA, in the 1950s, used a similar technology to fabricate a kind of glass that could selectively reflect light wavelengths. They achieved this by depositing a thin-film of metal on the glass.

With innumerable combinations of oxides, glass colors and patterns available, the possibilities to utilize this phenomenon for various useful purposes are endless.
The unusual properties of this cup have also inspired material scientists to create concepts for an invisibility cloak using modern nanofabrication technology. [Source]

I want to study interesting materials like these

If you think the Lycurgus cup, Wolverine’s claws and Aerogels (If you haven’t heard about it, you must definitely check this out!) are awesome. You can make a career in researching materials like these by making a foray into Materials Science and Engineering. Most good universities offer a course in it. It is a budding field, growing at a rapid pace, replete with real-world challenging conundrums waiting to be resolved.

4D Printing is Here

By Anupum Pant

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We had just started getting comfortable with printing objects in 3D, and 4D printing is already here. Early this year, in the month of April, Skylar Tibbits, an architect, designer and computer scientist at MIT, gave a revolutionary demonstration explaining their advances in the field of 4D printing at a TED conference. This was an initial proposal and it got things moving at a rapid pace.

Side note: In the world of 3D printing:

What is 4D printing?

At first 4D printing sounds like a catch phrase, it isn’t really just that. 4D printing is actually 1D better than 3D printing and it aims at making objects out of a 3D printer, that can reconfigure themselves into useful shapes, on their own. For instance, think of a non-living stick changing itself into a 3D cube as time passes. In short, 4D printing will enable us to create living objects without any living cells, micro-processors, chips or batteries involved. Sounds simple enough, but the promises are nothing less than extraordinary.

In the TED talk attached below, Skylar explains how a string of plastic placed in water can turn itself into the letters MIT. But, this was something that happened back in April. Things have moved further.

A few days back, Researchers at the University of Colorado Boulder revealed a successful test of their 4D printing technology. They were able to print out flat objects using normal plastic combined with a smart material which was able to turn into a cube on its own. Cubes are just the start.

According to scientists, in the future, 4D printing will probably churn out smart car bodies that would heal automatically, smart soldier uniforms and advanced building materials. Imagine a camouflage material that changes to match the surroundings, that could be the future. Or a pipe that contracts and expands to move water without pumps. Or a building material that builds itself into a structure. 4D printing could probably best suited for building in an extremely hostile environment like space. The possibilities are endless.

But, let us not get ahead of ourselves. It is almost impossible to predict what we’ll actually see in the future. Things have just started to happen in the field of 4D printing. But, it sure looks amazing. What will you build?

Why is a Metal Plate “Colder” Than a Plastic Plate?

by Anupum Pant

No, it isn’t!

What is Cold?

According to the dictionary, a body at a relatively lower temperature, especially when it is compared to the temperature of a human body is described as a colder one. So, any object below the normal human body temperature – about 37 degrees Celsius – is a cold thing. But wait a minute!

When you touch an object, what does it tell you about the temperature of the object? Can you really judge if it is a cold one or a hot one? Unfortunately, our bodies aren’t thermometers, we are not so smart when it comes to judging the temperature. Consider the following case.

A book and a steel plate kept in the same environment for a long time attain the same temperature eventually (it is called thermal equilibrium). This can be checked by using a thermometer on both the objects. But, when people are asked to touch a metal plate and a book, they find the former to be much cooler. You can try this out yourself by touching different materials around you. You’ll see how some things ‘feel colder’ while the others feel warmer. A YouTube channel Vertasium conducted a social experiment to record this on camera. See the video below:

There is no cold – only heat

So, in the video, ice melts faster, if kept on steel plate than on a plastic plate, even when the steel plate ‘feels colder’. Common sense dictates that the colder thing is supposed to sustain the ice block for a longer time, just like your refrigerator does. So why does the opposite happen?

A better way to understand this ‘contradiction’ (not really a contradiction) can be this:

According to thermodynamics, simply put, everything has heat in it. So, even a cold ice block has some amount of heat stored in it (say, around 273.15 Kelvin or 0 degree Celsius). When one object comes in contact with other object, it loses or gains heat till their temperatures get equal or till they attain ‘thermal equilibrium’. Which object loses heat and which one gains it, is decided by their relative temperatures. In case of ice and steel, ice has a lower temperature than steel (assuming it isn’t already freezing out there). Therefore, here, ice gains heat from steel till they attain the same temperature and ice melts.

Side note: The ice is also in contact with a relatively ‘hotter’ atmosphere. Hence, it gains heat from there also. In this case, we are only concerned about the steel and ice interaction.

Why does it melt faster on steel?

There is a particular property which depends on the kind of material and is called thermal conductivity. This is the parameter which decides which objects lose heat quicker and which ones do it slower.

Here, for instance, steel has a higher thermal conductivity than plastic. Hence, the steel plate gives away heat to the ice block faster than a plastic block does. As a result, ice melts faster on a steel plate than on a plastic one.

Incidentally, this effect can also be used to explain why one plate feels colder than the other, in our hands. Think of it like this, the ice is replaced by our hand. So, a steel plate, due to its better thermal conductivity, draws heat faster from our hand than a plastic plate. This makes us feel that the steel plate is colder than the plastic one.

As checked by a thermometer, both the plates have the same temperature, our bodies are only fooled into believing that the thing we feel is temperature; it isn’t. None of the plates is actually colder than the other (according to the dictionary – see first paragraph). We don’t feel the temperature. What we feel is actually the rate of heat being drawn away from our hand. Faster an object draws heat, the colder it feels.

Bricks Which Are Lighter Than Air

by Anupum Pant

What would smoke look and feel like, if you could solidify it?

Aerogels

Although, first made in 1931, Aerogels are relatively newer materials and a tremendous amount of research is being done on them everyday. Lightest solids ever, Aerogels weighing about seven times lesser than air have been made. Their extreme properties have given a fascinating field of interest to students and scientists. [Read the last paragraph]

How are they made?
Aerogels, also known as solid smoke or frozen smoke are extremely light materials. They are made by a process called sol-gel process which involves removing all the moisture from a specially made gel (Hypercritical Drying). Although the procedure may sound simple, there is a lot of technology involved in making them. Moreover, practically usable Aerogels which can endure moist conditions and high stress conditions are much more challenging to make. Also, it is very expensive to make them. [They can be made at home – with costly equipment of course]

Why is it so light? 
The whole lot of porosity left inside due to drying of the gel is what makes it so light. You can think of them as a sponge which is hard like pumice. But, when you think of a sponge, remember that mostly Aerogels aren’t very resilient. That means, unlike sponge they won’t get back into the previous shape after they’ve been pressed a lot. They are much sturdier/tighter than sponges. A small (not very small; due to very low density they occupy large space) piece of Aerogel weighing just 2 grams has been shown to hold a 2.5 kg brick without deforming. Poorly made Aerogels, on the other hand can also not be very sturdy. They would deform with a hard press of a finger and stay deformed.

How light are they?
Agreed, they can be lighter than air, but the practical mass varies greatly. And they don’t float in air because, with air present inside them, they are slightly heavier than air (weight of air inside + solid material), but can be made to float in air by replacing the air inside it with Hydrogen or Helium. Their lightness and density is completely dependent on the amount of porosity included during the fabrication – which can be controlled. Also, the kind of gel used to make it, affects the weight of the final block. So a block with 3 feet in length, breath and height can weigh anything from 1 kg to just 160 gm.

Aerographite, a carbon Aerogel made by German material scientists from Kiel University and the Hamburg University of Technology, was said to have weighed only 0.2 mg per cubic centimeter. It was 5000 times less dense than water and 6 times lighter than air (counting only the solid material’s weight of course). [Published Paper]

Graphene Aerogel: As if that wasn’t enough, recently, Chinese material scientists developed a lighter material than Aerographite. It was based on Graphene. A Graphene Aerogel; seven times lighter than air. This one, unlike other silica Aerogels, can recover like a sponge after getting deformed. [Published Paper]

Other Properties

Aerogels exhibit various other desirable properties which make them useful for a myriad of applications [See the Wikipedia Article]. For instance, they are very good insulators of heat. A nicely made Aerogel block which is just under a centimeter thick can protect things from a direct flame. Other desirable properties are high surface area, high thermal and acoustic resistivity, low dielectric constant, and low refractive index.

Aerogels absorb water or moisture from the air and even from human skin easily. Handling them with bare hands can cause blisters. But, the ones which repel water have been made successfully by altering fabrication parameters. Also, if particles of it are inhaled, it can cause problems. Hence, hand gloves and respiratory masks are used to handle them.

I want to study interesting materials like these

If you think Aerogels and Wolverine’s claws are interesting things. You can make a career in researching materials like these by making a foray into Materials Science and Engineering. Most good universities offer a course in it. It is a budding field, growing at a rapid pace with loads of opportunities waiting for you.