Tag Archives: adhesive tape

‘Scotch-tape’ technique for isolating graphene

The ‘scotch-tape’ technique is mythologized in the graphene origins story which has scientists, Andre Geim and Konstantin Novoselov, first isolating the material by using adhesive (aka ‘sticky’ tape or ‘scotch’ tape) as per my Oct. 7, 2010 posting,

The technique that Geim and Novoselov used to create the first graphene sheets both amuses and fascinates me (from the article by Kit Eaton on the Fast Company website),

The two scientists came up with the technique that first resulted in samples of graphene–peeling individual atoms-deep sheets of the material from a bigger block of pure graphite. The science here seems almost foolishly simple, but it took a lot of lateral thinking to dream up, and then some serious science to investigate: Geim and Novoselo literally “ripped” single sheets off the graphite by using regular adhesive tape. Once they’d confirmed they had grabbed micro-flakes of the material, Geim and Novoselo were responsible for some of the very early experiments into the material’s properties. Novel stuff indeed, but perhaps not so unexpected from a scientist (Geim) who the Nobel Committe notes once managed to make a frog levitate in a magnetic field.

A May 21, 2014 article about Geim who has won both a Nobel and an Ig Nobel (the only scientist to do so) and graphene by Sarah Lewis for Fast Company offers more details about the discovery,

The graphene FNE [Friday Night Experiments] began when Geim asked Da Jiang, a doctoral student from China, to polish a piece of graphite an inch across and a few millimeters thick down to 10 microns using a specialized machine. Partly due to a language barrier, Jiang polished the graphite down to dust, but not the ultimate thinness Geim wanted.

Helpfully, the Geim lab was also observing graphite using scanning tunneling microscopy (STM). The experimenters would clean the samples beforehand using Scotch tape, which they would then discard. “We took it out of the trash and just used it,” Novoselov said. The flakes of graphite on the tape from the waste bin were finer and thinner than what Jiang had found using the fancy machine. They weren’t one layer thick—that achievement came by ripping them some more with Scotch tape.

They swapped the adhesive for Japanese Nitto tape, “probably because the whole process is so simple and cheap we wanted to fancy it up a little and use this blue tape,” Geim said. Yet “the method is called the ‘Scotch tape technique.’ I fought against this name, but lost.”

Scientists elsewhere have been inspired to investigate the process in minute detail as per a June 27, 2014 news item on Nanowerk,

The simplest mechanical cleavage technique using a primitive “Scotch” tape has resulted in the Nobel-awarded discovery of graphenes and is currently under worldwide use for assembling graphenes and other two-dimensional (2D) graphene-like structures toward their utilization in novel high-performance nanoelectronic devices.

The simplicity of this method has initiated a booming research on 2D materials. However, the atomistic processes behind the micromechanical cleavage have still been poorly understood.

A June 27, 2014 MANA (International Center for Materials Nanoarchitectoinics) news release, which originated the news item, provides more information,

A joined team of experimentalists and theorists from the International Center for Young Scientists, International Center for Materials Nanoarchitectonics and Surface Physics and Structure Unit of the National Institute for Materials Science, National University of Science and Technology “MISiS” (Moscow, Russia), Rice University (USA) and University of Jyväskylä (Finland) led by Daiming Tang and Dmitri Golberg for the first time succeeded in complete understanding of physics, kinetics and energetics behind the regarded “Scotch-tape” technique using molybdenum disulphide (MoS2) atomic layers as a model material.

The researchers developed a direct in situ probing technique in a high-resolution transmission electron microscope (HRTEM) to investigate the mechanical cleavage processes and associated mechanical behaviors. By precisely manipulating an ultra-sharp metal probe to contact the pre-existing crystalline steps of the MoS2 single crystals, atomically thin flakes were delicately peeled off, selectively ranging from a single, double to more than 20 atomic layers. The team found that the mechanical behaviors are strongly dependent on the number of layers. Combination of in situ HRTEM and molecular dynamics simulations reveal a transformation of bending behavior from spontaneous rippling (< 5 atomic layers) to homogeneous curving (~ 10 layers), and finally to kinking (20 or more layers).

By considering the force balance near the contact point, the specific surface energy of a MoS2 monoatomic layer was calculated to be ~0.11 N/m. This is the first time that this fundamentally important property has directly been measured.

After initial isolation from the mother crystal, the MoS2 monolayer could be readily restacked onto the surface of the crystal, demonstrating the possibility of van der Waals epitaxy. MoS2 atomic layers could be bent to ultimate small radii (1.3 ~ 3.0 nm) reversibly without fracture. Such ultra-reversibility and extreme flexibility proves that they could be mechanically robust candidates for the advanced flexible electronic devices even under extreme folding conditions.

Here’s a link to and a citation for the research paper,

Nanomechanical cleavage of molybdenum disulphide atomic layers by Dai-Ming Tang, Dmitry G. Kvashnin, Sina Najmaei, Yoshio Bando, Koji Kimoto, Pekka Koskinen, Pulickel M. Ajayan, Boris I. Yakobson, Pavel B. Sorokin, Jun Lou, & Dmitri Golberg. Nature Communications 5, Article number: 3631 doi:10.1038/ncomms4631 Published 03 April 2014

This paper is behind a paywall but there is a free preview available through ReadCube Access.

Eeek! The sticky tape is coming after us!

Fingers emerged from sticky tape to form claws in a research project conducted at Purdue University (Indiana, US), which will be presented at a meeting of the Materials Research Society (MRS) in Boston from Sunday (Nov. 25) to Nov. 30, 2012. The Nov. 20, 2012 news release on EurekAlert describes the new ‘smart’ material,

Researchers used a laser to form slender half-centimeter-long fingers out of the tape. When exposed to water, the four wispy fingers morph into a tiny robotic claw that captures water droplets.

The innovation could be used to collect water samples for environmental testing, said Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering.

“It  [the tape] can be micromachined into different shapes and works as an inexpensive smart material that interacts with its environment to perform specific functions,” he said.

Doctoral student Manuel Ochoa came up with the idea. While using tape to collect pollen, he noticed that it curled when exposed to humidity. The cellulose-acetate absorbs water, but the adhesive film repels water.

“So, when one side absorbs water it expands, the other side stays the same, causing it to curl,” Ziaie said.

A laser was used to machine the tape to a tenth of its original thickness, enhancing this curling action. The researchers coated the graspers with magnetic nanoparticles so that they could be collected with a magnet.

“Say you were sampling for certain bacteria in water,” Ziaie said. “You could drop a bunch of these and then come the next day and collect them.”

Sticky tape is one of  my favourite pieces of science equipment along with inkjet printers and ‘Shrinky Dinks’ as I noted in my Nov. 16, 2012 posting about bio-ink. The Nov. 20, 2012 news release by Emil Venere can also be found on the Purdue University website along with photos and other materials such as this animated GIF of the gripper closing available at https://engineering.purdue.edu/ZBML/img/research/plain-gripper-closing.gif.

Graphene, the Nobel Prize, and levitating frogs

As you may have heard, two  scientists (Andre Geim and Konstantin Novoselov) who performed groundbreaking research on graphene [Nov. 29, 2010: I corrected this entry Nov. 26, 2010 which originally stated that these researchers discovered graphene] have been awarded the 2010 Nobel Prize for Physics. In honour of their award, the journal, Nature Materials, is giving free access to  a 2007 article authored by the scientists. From the news item on Nanowerk,

The 2007 landmark article in Nature Materials “The rise of graphene” by the just announced winners of the 2010 Nobel prize in physics, Andre Geim and Kosta Novoselov, has now been made available as a free access article.

Abstract:

Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here.

Here’s a description of the scientists and their work from the BBC News article by Paul Rincon,

Prof Geim, 51, is a Dutch national while Dr Novoselov, 36, holds British and Russian citizenship. Both are natives of Russia and started their careers in physics there.

The Nobels are valued at 10m Swedish kronor (£900,000; 1m euros; $1.5m).

They first worked together in the Netherlands before moving to the UK. They were based at the University of Manchester when they published their groundbreaking research paper on graphene in October 2004.

Dr Novoselov is among the youngest winners of a prize that normally goes to scientists with decades of experience.

Graphene is a form of carbon. It is a flat layer of carbon atoms tightly packed into a two-dimensional honeycomb arrangement.

Because it is so thin, it is also practically transparent. As a conductor of electricity it performs as well as copper, and as a conductor of heat it outperforms all other known materials.

The unusual electronic, mechanical and chemical properties of graphene at the molecular scale promise ultra-fast transistors for electronics.

Some scientists have predicted that graphene could one day replace silicon – which is the current material of choice for transistors.

It could also yield incredibly strong, flexible and stable materials and find applications in transparent touch screens or solar cells.

Geim and Novoselov first isolated fine sheets of graphene from the graphite which is widely used in pencils.

A layer of graphite 1mm thick actually consists of three million layers of graphene stacked on top of one another.

The technique that Geim and Novoselov used to create the first graphene sheets both amuses and fascinates me (from the article by Kit Eaton on the Fast Company website),

The two scientists came up with the technique that first resulted in samples of graphene–peeling individual atoms-deep sheets of the material from a bigger block of pure graphite. The science here seems almost foolishly simple, but it took a lot of lateral thinking to dream up, and then some serious science to investigate: Geim and Novoselo literally “ripped” single sheets off the graphite by using regular adhesive tape. Once they’d confirmed they had grabbed micro-flakes of the material, Geim and Novoselo were responsible for some of the very early experiments into the material’s properties. Novel stuff indeed, but perhaps not so unexpected from a scientist (Geim) who the Nobel Committe notes once managed to make a frog levitate in a magnetic field.

I’ll get to the levitating frog in a minute but first the bit about using regular adhesive tape to peel off single sheets only atoms thick of graphite from a larger block of the stuff reminds me of how scientists at Northwestern University are using shrinky dinks (a child’s craft material) to create large scale nanopatterns cheaply (my Aug. 16, 2010 posting).

It’s reassuring to me that despite all of the high tech equipment that costs the earth, scientists still use fairly mundane, inexpensive objects to do some incredibly sophisticated work. The other thing I find reassuring is that Novoselov probably was not voted ‘most likely to be awarded a Nobel Prize’. Interestingly, Novoselov’s partner, Geim, was not welcomed into a physics career with open arms. From the news item on physoorg.com,

Konstantin Novoselov, the Russian-born physicist who shared this year’s Nobel prize, struggled with physics as a student and was awarded a handful of B grades, his university said Wednesday.

The Moscow Physics and Technology University (MFTI) posted report cards on its website for Novoselov, who at 36 won the Nobel prize for physics with his research partner Andre Geim.

The reports reveal that he gained a handful of B grades in his term reports for theoretical and applied physics from 1991 to 1994.

He was also not strong on physical education — a compulsory subject at Russian universities — gaining B grades. And while he now lives in Britain, he once gained a C grade for English.

The university also revealed documents on Nobel prize winner Geim, who studied at the same university from 1976 to 1982. His brilliant academic career was only marred by a few B-grades for Marxist political economy and English.

Geim was turned down when he applied first to another Moscow university specialising in engineering and physics, and worked as a machinist at a factory making electrical instruments for eight months.

Given the increasing emphasis on marks, in Canadian universities at least, I noticed that Novoselov was not a straight-A student. As for Geim, it seems the fact that his father was German posed a problem. (You can find more details in the physorg.com article.)

As for levitating frogs, I first found this information in particle physicist Jon Butterworth’s October 5, 2010 posting on his Guardian blog,

Geim is also well known (or as his web page puts it “notorious”) for levitating frogs. This is a demonstration of the peculiar fact that all materials have some magnetism, albeit very weak in most cases, and that if you put them in a high enough magnetic field you can see the effects – and make them fly.

Why frogs? Well, no frogs were harmed in the experiments. But also, magnetism is a hugely important topic in physics that can seem a little dry to students …

I hunted down a video of the levitating frog on youtube,

As a particle physicist, Butterworth notes that the graphene work is outside his area of expertise so if you’re looking for a good, general explanation with some science detail added in for good measure, I’d suggest reading his succinct description.