Tag Archives: materials science

3D Printing Magic


If you’ve visited this blog before you know I’m a great fan of 3D printing. Though some uses, such as printing 3D selfies, seem dubious at best. So, when Carbon3D unveiled its fundamentally different, and better, approach to 3D printing I was intrigued. The company uses an approach called continuous liquid interface production (CLIP), which seems to construct objects from a magical ooze. Check out the video — you’ll be enthralled. The future is here.

Learn more about Carbon3D here.

From Wired:

EVEN IF YOU have little interest in 3-D printing, you’re likely to find  Carbon3D’s Continuous Liquid Interface Production (CLIP) technology fascinating. Rather than the time-intensive printing of a 3-D object layer by layer like most printers, Carbon3D’s technique works 25 to 100 times faster than what you may have seen before, and looks a bit like Terminator 2‘s liquid metal T-1000 in the process.

CLIP creations grow out of a pool of UV-sensitive resin in a process that’s similar to the way laser 3-D printers work, but at a much faster pace. Instead of the laser used in conventional 3-D printers, CLIP uses an ultraviolet projector on the underside of a resin tray to project an image for how each layer should form. Light shines through an oxygen-permeable window onto the resin, which hardens it. Areas of resin that are exposed to oxygen don’t harden, while those that are cut off form the 3-D printed shape.

In practice, all that physics translates to unprecedented 3-D printing speed. At this week’s TED Conference in Vancouver, Carbon3D CEO and co-founder Dr. Joseph DeSimone demonstrated the printer onstage with a bit of theatrical underselling, wagering that his creation could produce in 10 minutes a geometric ball shape that would take a regular 3-D printer up to 10 hours. The CLIP process churned out the design in a little under 7 minutes.

Read the entire story here.

Video courtesy of Carbon3D.

Waterproof Clothes

Another technology barrier falls by the wayside as textile and materials science researchers perfect an ultra-hydrophobic spray. No more getting your clothes wet in a downpour.

From the Guardian:

I hate being rained on. I especially hate it when it’s cold. You’d have thought that with all our 21st-century Google-Glass exploring-Mars engineering marvellousness, we would have made more progress on the problem of rain. But no. The umbrella is a few thousand years old and is nowhere near an optimal solution, especially in blustery windy weather. Wet-weather clothing works if you wear it, but most people don’t because it looks so awful.

From a materials-science perspective, the best solution for the British weather would be an invisible waterproof coating that you can spray on the clothes you actually do want to wear. Excitingly such materials have now been invented; they borrow tricks from nature, and they may yet get us singing in the rain.

Traditional waterproofing involves materials that are hydrophobic – in other words molecules that repel water. Waxes and other oily materials fall into this category because of the way they share their electrons at an atomic scale. Water molecules are polar, which means they have plus and minus charged ends. Waxes and oils prefer their electrons more equally distributed and so find it hard to conform to the polarity of water, and in the stand-off they repel each other. Hence oil and water don’t mix. This hydrophobic behaviour is bad for vinaigrettes but good for waterproofing.

Nature uses this trick too but is much better at it. Go into a garden during a rain shower and have a look at how many leaves repel water so effectively that water droplets sit like jewels glistening on their surface. Lotus leaves have long been known to have this superhydrophobic property, but no one knew why until electron microscopes revealed something very odd about the surface of the lotus leaf. There is a waxy material there, yes, but it is arranged on the surface in the form of billions of tiny microscopic bumps. When a drop of water sits on a hydrophobic surface it tries to minimise its area of contact, because it wants to minimise its interaction with the non-polar waxy material.

The bumps on the lotus leaf drastically increase this area of waxiness, forcing the droplet to sit up precariously on the tips of the bumps. In this, the Cassie-Baxter state, the droplet becomes very mobile and quickly slides off the leaf. So by manipulating just the bumpiness of its surface, lotus leaves are far better at repelling water.

The mobility of the droplets has another effect. By zooming around the surface of the leaf rather than sticking, the droplets of water collect small particles of dust, hoovering them up. This cleaning mechanism of these superhydrophobic surfaces is called the lotus effect.

Superhydrophobic surfaces have been synthesised and studied in labs for decades, but it is only recently that commercial versions have been produced. Now there are quite a few coming on to the market (eg neverwet.com), and they are impressive – when water is poured on to these surfaces it behaves like mercury and bounces off.

The trick, as with the lotus leaf, is to create a microscale patterned non-polar surface. The fact that these sophisticated surfaces can be sprayed out of a can is a triumph of nanotechnology. As with the lotus leaf these coatings not only keep things dry, they also keep them clean, since a lot of what constitutes dirt arrives on your clothes as splashes of liquid that subsequently dry leaving a residue. If the droplets of bolognese sauce, curry or mud don’t stick but bounce off, then they won’t leave a stain.

There are many other applications for these coatings, such as reducing the window cleaning bills on skyscrapers; keeping paint clean on cars; making sofas immune to red wine; and in its key role as waterproofer extraordinaire, keeping your mobile phone safe when it is dropped down the loo.

Read the entire article here.

A Window that Vacuums Sound

We are all familiar with double-glazed windows that reduce transmission of sound by way of a partial vacuum between the two or more panes of glass. However, open a double-glazed window to let in some fresh air and the benefit of the sound reduction is gone. So, what if you could invent a window that lets in air but cuts out the noise pollution? Sounds impossible. But not to materials scientists Sang-Hoon Kim and Seong-Hyun Lee from South Korea.

From Technology Review:

Noise pollution is one of the bugbears of modern life. The sound of machinery, engines, neighbours and the like can seriously affect our quality of life and that of the other creatures that share this planet.

But insulating against sound is a difficult and expensive business. Soundproofing generally works on the principle of transferring sound from the air into another medium which absorbs and attenuates it.

So the notion of creating a barrier that absorbs sound while allowing the free of passage of air seems, at first thought, entirely impossible. But that’s exactly what Sang-Hoon Kima at the Mokpo National Maritime University in South Korea and Seong-Hyun Lee at the Korea Institute of Machinery and Materials, have achieved.

These guys have come up with a way to separate sound from the air in which it travels and then to attenuate it. This has allowed them to build a window that allows air to flow but not sound.

The design is relatively simple and relies on two exotic acoustic phenomenon. The first is to create a material with a negative bulk modulus.

A material’s bulk modulus is essentially its resistance to compression and this is an important factor in determining the speed at which sound moves through it. A material with a negative bulk modulus exponentially attenuates any sound passing through it.

However, it’s hard to imagine a solid material having a negative bulk modulus, which is where a bit of clever design comes in handy.

Kima and Lee’s idea is to design a sound resonance chamber in which the resonant forces oppose any compression. With careful design, this leads to a negative bulk modulus for a certain range of frequencies.

Their resonance chamber is actually very simple—it consists of two parallel plates of transparent acrylic plastic about 150 millimetres square and separated by 40 millimetres, rather like a section of double-glazing about the size of a paperback book.

This chamber is designed to ensure that any sound resonating inside it acts against the way the same sound compresses the chamber. When this happens the bulk modulus of the entire chamber is negative.

An important factor in this is how efficiently the sound can get into the chamber and here Kima and Lee have another trick. To maximise this efficiency, they drill a 50 millimetre hole through each piece of acrylic. This acts as a diffraction element causing any sound that hits the chamber to diffract strongly into it.

The result is a double-glazed window with a negative bulk modulus that strongly attenuates the sound hitting it.

Kima and Lee use their double-glazing unit as a building block to create larger windows. In tests with a 3x4x3 “wall” of building blocks, they say their window reduces sound levels by 20-35 decibels over a sound range of 700 Hz to 2,200 Hz. That’s a significant reduction.

And by using extra building blocks with smaller holes, they can extend this range to cover lower frequencies.

What’s handy about these windows is that holes through them also allow the free flow of air, giving ample ventilation as well.

Read the entire article here.