Tag Archives: Emil Venere

Fundamental mechanical behaviour of cellulose nanocrystals (aka nanocrystalline cellulose)

Emil Venere at Purdue University offers an excellent explanation of why there’s so much international interest in cellulose nanocrystals (CNC aka, nanocrystalline cellulose [NCC]) in his Dec. 16, 2013 Purdue University (Indiana, US) news release (also on EurekAlert), Note: A link has been removed,

The same tiny cellulose crystals that give trees and plants their high strength, light weight and resilience, have now been shown to have the stiffness of steel.

The nanocrystals might be used to create a new class of biomaterials with wide-ranging applications, such as strengthening construction materials and automotive components.

Calculations using precise models based on the atomic structure of cellulose show the crystals have a stiffness of 206 gigapascals, which is comparable to steel, said Pablo D. Zavattieri, a Purdue University assistant professor of civil engineering.

Here’s an image of the cellulose crystals being examined,

This transmission electron microscope image shows cellulose nanocrystals, tiny structures that give trees and plants their high strength, light weight and resilience. The nanocrystals might be used to create a new class of biomaterials that would have a wide range of applications. (Purdue Life Sciences Microscopy Center)

This transmission electron microscope image shows cellulose nanocrystals, tiny structures that give trees and plants their high strength, light weight and resilience. The nanocrystals might be used to create a new class of biomaterials that would have a wide range of applications. (Purdue Life Sciences Microscopy Center)

You’ll notice this image is not enhanced and made pretty as compared to the images in my Dec. 16, 2013 posting about Bristol University’s Art of Science competition. It takes a lot of work to turn the types of images scientists use into ‘art’.

Getting back to the CNC, this news release was probably written by someone who’s not familiar with the other work being done in the field (university press officers typically write about a wide range of topics and cannot hope to have in depth knowledge on each topic) and so it’s being presented as if it is brand new information. In fact, there has been several years work done in five other national jurisdictions that I know of (Sweden, Finland, Canada, Brazil, and Israel) and there are likely more. That’s not including other US states pursuing research in this area, notably Wisconsin.

What I (taking into account  my limitations) find particularly exciting in this work is the detail they’ve been able to determine and the reference to quantum mechanics. Here’s more from the news release (Note: Links have been removed),

“It is very difficult to measure the properties of these crystals experimentally because they are really tiny,” Zavattieri said. “For the first time, we predicted their properties using quantum mechanics.”

The nanocrystals are about 3 nanometers wide by 500 nanometers long – or about 1/1,000th the width of a grain of sand – making them too small to study with light microscopes and difficult to measure with laboratory instruments.

The findings represent a milestone in understanding the fundamental mechanical behavior of the cellulose nanocrystals.

“It is also the first step towards a multiscale modeling approach to understand and predict the behavior of individual crystals, the interaction between them, and their interaction with other materials,” Zavattieri said. “This is important for the design of novel cellulose-based materials as other research groups are considering them for a huge variety of applications, ranging from electronics and medical devices to structural components for the automotive, civil and aerospace industries.”

From an applications perspective (which is what excites so much international interest),

The cellulose nanocrystals represent a potential green alternative to carbon nanotubes for reinforcing materials such as polymers and concrete. Applications for biomaterials made from the cellulose nanocrystals might include biodegradable plastic bags, textiles and wound dressings; flexible batteries made from electrically conductive paper; new drug-delivery technologies; transparent flexible displays for electronic devices; special filters for water purification; new types of sensors; and computer memory.

Cellulose could come from a variety of biological sources including trees, plants, algae, ocean-dwelling organisms called tunicates, and bacteria that create a protective web of cellulose.

“With this in mind, cellulose nanomaterials are inherently renewable, sustainable, biodegradable and carbon-neutral like the sources from which they were extracted,” Moon said. “They have the potential to be processed at industrial-scale quantities and at low cost compared to other materials.”

Biomaterials manufacturing could be a natural extension of the paper and biofuels industries, using technology that is already well-established for cellulose-based materials.

“Some of the byproducts of the paper industry now go to making biofuels, so we could just add another process to use the leftover cellulose to make a composite material,” Moon said. “The cellulose crystals are more difficult to break down into sugars to make liquid fuel. So let’s make a product out of it, building on the existing infrastructure of the pulp and paper industry.”

Their surface can be chemically modified to achieve different surface properties.

“For example, you might want to modify the surface so that it binds strongly with a reinforcing polymer to make a new type of tough composite material, or you might want to change the chemical characteristics so that it behaves differently with its environment,” Moon said.

Zavattieri plans to extend his research to study the properties of alpha-chitin, a material from the shells of organisms including lobsters, crabs, mollusks and insects. Alpha-chitin appears to have similar mechanical properties as cellulose.

“This material is also abundant, renewable and waste of the food industry,” he said.

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

Anisotropy of the Elastic Properties of Crystalline Cellulose Iβ from First Principles Density Functional Theory with Van der Waals Interactions by Fernando L. Dri, Louis G. Hector Jr., Robert J. Moon, Pablo D. Zavattieri.  Cellulose December 2013, Volume 20, Issue 6, pp 2703-2718. 10.1007/s10570-013-0071-8

This paper is behind a paywall although you can preview the first few pages.

Christmas-tree shaped ‘4-D’ nanowires

This Dec. 5, 2012 news item on Nanowerk features a seasonal approach to a study about ‘4-D’ nanowires,

A new type of transistor shaped like a Christmas tree has arrived just in time for the holidays, but the prototype won’t be nestled under the tree along with the other gifts.

“It’s a preview of things to come in the semiconductor industry,” said Peide “Peter” Ye, a professor of electrical and computer engineering at Purdue University.

Researchers from Purdue and Harvard universities created the transistor, which is made from a material that could replace silicon within a decade. Each transistor contains three tiny nanowires made not of silicon, like conventional transistors, but from a material called indium-gallium-arsenide. The three nanowires are progressively smaller, yielding a tapered cross section resembling a Christmas tree.

Sadly, Purdue University (Indiana, US) will not be releasing any images to accompany their Dec. 4, 2012 news release (which originated the news item) about the ‘4-D’ transistor  until Saturday, Dec. 8, 2012.  So here’s an image of a real Christmas tree from the National Christmas Tree Organization’s Common Tree Characteristics webpage,

Douglas Fir Christmas tree from http://www.realchristmastrees.org/dnn/AllAboutTrees/TreeCharacteristics.aspx

 

The Purdue University news release written by Emil Venere provides more detail about the work,

“A one-story house can hold so many people, but more floors, more people, and it’s the same thing with transistors,” Ye said. “Stacking them results in more current and much faster operation for high-speed computing. This adds a whole new dimension, so I call them 4-D.”

The work is led by Purdue doctoral student Jiangjiang Gu and Harvard postdoctoral researcher Xinwei Wang.

The newest generation of silicon computer chips, introduced this year, contain transistors having a vertical 3-D structure instead of a conventional flat design. However, because silicon has a limited “electron mobility” – how fast electrons flow – other materials will likely be needed soon to continue advancing transistors with this 3-D approach, Ye said.

Indium-gallium-arsenide is among several promising semiconductors being studied to replace silicon. Such semiconductors are called III-V materials because they combine elements from the third and fifth groups of the periodic table.

Transistors contain critical components called gates, which enable the devices to switch on and off and to direct the flow of electrical current. Smaller gates make faster operation possible. In today’s 3-D silicon transistors, the length of these gates is about 22 nanometers, or billionths of a meter.

The 3-D design is critical because gate lengths of 22 nanometers and smaller do not work well in a flat transistor architecture. Engineers are working to develop transistors that use even smaller gate lengths; 14 nanometers are expected by 2015, and 10 nanometers by 2018.

However, size reductions beyond 10 nanometers and additional performance improvements are likely not possible using silicon, meaning new materials will be needed to continue progress, Ye said.

Creating smaller transistors also will require finding a new type of insulating, or “dielectric” layer that allows the gate to switch off. As gate lengths shrink smaller than 14 nanometers, the dielectric used in conventional transistors fails to perform properly and is said to “leak” electrical charge when the transistor is turned off.

Nanowires in the new transistors are coated with a different type of composite insulator, a 4-nanometer-thick layer of lanthanum aluminate with an ultrathin, half-nanometer layer of aluminum oxide. The new ultrathin dielectric allowed researchers to create transistors made of indium-gallium- arsenide with 20-nanometer gates, which is a milestone, Ye said.

This work will be presented at the 2012 International Electron Devices (IEEE [Institute of Electrical and Electronics Engineers]) meeting in San Francisco, California, Dec. 10 – 12, 2012 (as per the information on the registration page) with the two papers written by the team will be published in the proceedings.

I have a full list of the authors, from the news release,

The authors of the research papers are Gu [Jiangjiang Gu]; Wang [Xinwei Wang]; Purdue doctoral student H. Wu; Purdue postdoctoral research associate J. Shao; Purdue doctoral student A. T. Neal; Michael J. Manfra, Purdue’s William F. and Patty J. Miller Associate Professor of Physics; Roy Gordon, Harvard’s Thomas D. Cabot Professor of Chemistry; and Ye [Peide “Peter” Ye].

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.

Blood, tears, and urine for use in diagnostic tools

Frankly, I’d rather just spit into a cup or onto a slide for diagnostic tests than having to supply urine or have my blood drawn. I don’t think that day has arrived yet but scientists at Purdue University (Indiana, US) have made a breakthrough. From the Aug. 23, 2012 news item on ScienceDaily,

Researchers have created a new type of biosensor that can detect minute concentrations of glucose in saliva, tears and urine and might be manufactured at low cost because it does not require many processing steps to produce.

“It’s an inherently non-invasive way to estimate glucose content in the body,” said Jonathan Claussen, a former Purdue University doctoral student and now a research scientist at the U.S. Naval Research Laboratory. “Because it can detect glucose in the saliva and tears, it’s a platform that might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing. We are proving its functionality.”

Claussen and Purdue doctoral student Anurag Kumar led the project, working with Timothy Fisher, a Purdue professor of mechanical engineering; D. Marshall Porterfield, a professor of agricultural and biological engineering; and other researchers at the university’s Birck Nanotechnology Center.

The originating Aug. 20, 2012 Purdue University news release by Emil Venere provides details as to how this biosensor works,

The sensor has three main parts: layers of nanosheets resembling tiny rose petals made of a material called graphene, which is a single-atom-thick film of carbon; platinum nanoparticles; and the enzyme glucose oxidase.

Each petal contains a few layers of stacked graphene. The edges of the petals have dangling, incomplete chemical bonds, defects where platinum nanoparticles can attach. Electrodes are formed by combining the nanosheet petals and platinum nanoparticles. Then the glucose oxidase attaches to the platinum nanoparticles. The enzyme converts glucose to peroxide, which generates a signal on the electrode.

“Typically, when you want to make a nanostructured biosensor you have to use a lot of processing steps before you reach the final biosensor product,” Kumar said. “That involves lithography, chemical processing, etching and other steps. The good thing about these petals is that they can be grown on just about any surface, and we don’t need to use any of these steps, so it could be ideal for commercialization.”

In addition to diabetes testing, the technology might be used for sensing a variety of chemical compounds to test for other medical conditions.

Here’s a representation of the ‘rose petal’ nanosheets,

These color-enhanced scanning electron microscope images show nanosheets resembling tiny rose petals. The nanosheets are key components of a new type of biosensor that can detect minute concentrations of glucose in saliva, tears and urine. The technology might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing. (Purdue University photo/Jeff Goecker)
Download Photo

My most recent piece, prior to this, about less invasive diagnostic tests was this May 8, 2012 posting on a handheld diagnostic device that tests your breath for disease.

Brains in the US Congress

Tomorrow, May 24, 2012, Jean Paul Allain, associate professor of nuclear engineering at Purdue University (Illinois) will be speaking to members of the US Congress about repairing brain injuries using nanotechnology-enabled bioactive coatings for stents. From the May 21, 2012 news item on Nanowerk,

“Stents coated with a bioactive coating might be inserted at the site of an aneurism to help heal the inside lining of the blood vessel,” said Jean Paul Allain, an associate professor of nuclear engineering. “Aneurisms are saclike bulges in blood vessels caused by weakening of artery walls. We’re talking about using a regenerative approach, attracting cells to reconstruct the arterial wall.”

He will speak before Congress on Thursday (May 24) during the first Brain Mapping Day to discuss the promise of nanotechnology in treating brain injury and disease.

The May 21, 2012 news release (by Emil Venere) for Purdue University offers insight into some of the difficulties of dealing with aneurysms using today’s technologies,

Currently, aneurisms are treated either by performing brain surgery, opening the skull and clipping the sac, or by inserting a catheter through an artery into the brain and implanting a metallic coil into the balloon-like sac.

Both procedures risk major complications, including massive bleeding or the formation of potentially fatal blood clots.

“The survival rate is about 50/50 or worse, and those who do survive could be impaired,” said Allain, who holds a courtesy appointment with materials engineering and is affiliated with the Birck Nanotechnology Center in Purdue’s Discovery Park.

Allain goes on to explain how his team’s research addresses these issues (from the May 21, 2012 Purdue University news release),

Cells needed to repair blood vessels are influenced by both the surface texture – features such as bumps and irregular shapes as tiny as 10 nanometers wide – as well as the surface chemistry of the stent materials.

“We are learning how to regulate cell proliferation and growth by tailoring both the function of surface chemistry and topology,” Allain said. “There is correlation between surface chemistry and how cells send signals back and forth for proliferation. So the surface needs to be tailored to promote regenerative healing.”

The facility being used to irradiate the stents – the Radiation Surface Science and Engineering Laboratory in Purdue’s School of Nuclear Engineering – also is used for work aimed at developing linings for experimental nuclear fusion reactors for power generation.

Irradiating materials with the ion beams causes surface features to “self-organize” and also influences the surface chemistry, Allain said.

The stents are made of nonmagnetic materials, such as stainless steel and an alloy of nickel and titanium. Only a certain part of the stents is rendered magnetic to precisely direct the proliferation of cells to repair a blood vessel where it begins bulging to form the aneurism.

Researchers will study the stents using blood from pigs during the first phase in collaboration with the Walter Reed National Military Medical Center.

The stent coating’s surface is “functionalized” so that it interacts properly with the blood-vessel tissue. Some of the cells are magnetic naturally, and “magnetic nanoparticles” would be injected into the bloodstream to speed tissue regeneration. Researchers also are aiming to engineer the stents so that they show up in medical imaging to reveal how the coatings hold up in the bloodstream.

The research is led by Allain and co-principal investigator Lisa Reece of the Birck Nanotechnology Center. This effort has spawned new collaborations with researchers around the world including those at Universidad de Antioquía, University of Queensland. The research also involves doctoral students Ravi Kempaiah and Emily Walker.

The work is funded with a three-year, $1.5 million grant from the U.S. Army. Cells needed to repair blood vessels are influenced by both the surface texture – features such as bumps and irregular shapes as tiny as 10 nanometers wide – as well as the surface chemistry of the stent materials.

As I find the international flavour to the pursuit of science quite engaging, I want to highlight this bit in the May 21, 2012 news item on Nanowerk which mentions a few other collaborators on this project,

Purdue researchers are working with Col. Rocco Armonda, Dr. Teodoro Tigno and other neurosurgeons at Walter Reed National Military Medical Center in Bethesda, Md. Collaborations also are planned with research scientists from the University of Queensland in Australia, Universidad de Antioquía and Universidad de Los Andes, both in Colombia.

The US Congress is not the only place to hear about this work, Allain will also be speaking in Toronto at the 9th Annual World Congress of Society for Brain Mapping & Therapeutics (SBMT) being held June 2 – 4, 2012.

Music can recharge sensors in your body

According to a Jan.26, 2012 news item written by Emil Venere at Purdue University and posted on Nanowerk, researchers have found a new way to recharge batteries in new medical sensors that could be implanted in individuals stricken with aneurysms or bladder incontinence due to paralysis. From the news item,

“You would only need to do this for a couple of minutes every hour or so to monitor either blood pressure or pressure of urine in the bladder,” Ziaie [Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering] said. “It doesn’t take long to do the measurement.”

Findings are detailed in a paper (“A Novel Electromechanical Interrogation Scheme for Implantable Passive Transponders”) to be presented during the IEEE [Institute of Electrical and Electronics Engineers] MEMS [Micro Electro Mechanical Systems] 2012 conference, which will be Jan. 29 to Feb. 2 in Paris. The paper was written by doctoral student Albert Kim, research scientist Teimour Maleki and Ziaie.

“This paper demonstrates the feasibility of the concept,” he said.

As you may have guessed from that last line, this hasn’t been tried on people. According to the news item, the concept was tested using a water-filled balloon.

I checked out Venere’s Jan. 26, 2012 news release on the Purdue University website and am excerpting a few details about how these medical sensors work,

The sensor is capable of monitoring pressure in the urinary bladder and in the sack of a blood vessel damaged by an aneurism. Such a technology could be used in a system for treating incontinence in people with paralysis by checking bladder pressure and stimulating the spinal cord to close the sphincter that controls urine flow from the bladder. More immediately, it could be used to diagnose incontinence. The conventional diagnostic method now is to insert a probe with a catheter, which must be in place for several hours while the patient remains at the hospital.

The writer goes on to describe some of the reasons for why this new technology is being pursued,

“A wireless implantable device could be inserted and left in place, allowing the patient to go home while the pressure is monitored,” Ziaie said.

The new technology offers potential benefits over conventional implantable devices, which either use batteries or receive power through a property called inductance, which uses coils on the device and an external transmitter. Both approaches have downsides. Batteries have to be replaced periodically, and data are difficult to retrieve from devices that use inductance; coils on the implanted device and an external receiver must be lined up precisely, and they can only be about a centimeter apart.

The following image is  the researchers’ new sensor, balanced on a coin,

Researchers have created a new type of miniature pressure sensor, shown here, designed to be implanted in the body. Acoustic waves from music or plain tones drive a vibrating device called a cantilever, generating a charge to power the sensor. (Birck Nanotechnology Center, Purdue University)

I found the description of how the cantilever works and can be recharged quite interesting,

The heart of the sensor is a vibrating cantilever, a thin beam attached at one end like a miniature diving board. Music within a certain range of frequencies, from 200-500 hertz, causes the cantilever to vibrate, generating electricity and storing a charge in a capacitor …

The cantilever beam is made from a ceramic material called lead zirconate titanate, or PZT, which is piezoelectric, meaning it generates electricity when compressed. The sensor is about 2 centimeters long …

A receiver that picks up the data from the sensor could be placed several inches from the patient. Playing tones within a certain frequency range also can be used instead of music.

“But a plain tone is a very annoying sound,” Ziaie said. “We thought it would be novel and also more aesthetically pleasing to use music.”

Researchers experimented with four types of music: rap, blues, jazz and rock.

“Rap is the best because it contains a lot of low frequency sound, notably the bass,” Ziaie said.

“The music reaches the correct frequency only at certain times, for example, when there is a strong bass component,” he said. “The acoustic energy from the music can pass through body tissue, causing the cantilever to vibrate.”

When the frequency falls outside of the proper range, the cantilever stops vibrating, automatically sending the electrical charge to the sensor, which takes a pressure reading and transmits data as radio signals. Because the frequency is continually changing according to the rhythm of a musical composition, the sensor can be induced to repeatedly alternate intervals of storing charge and transmitting data.

“You would only need to do this for a couple of minutes every hour or so to monitor either blood pressure or pressure of urine in the bladder,” Ziaie said. “It doesn’t take long to do the measurement.”

It’s usually a long time from testing a concept (in this case, on a water balloon) to bringing a product to the marketplace. In the meantime, I wonder if this concept will work in the ‘wild’ where people are exposed to rap music accidentally or they like to listen to it themselves, all day long, or they loathe rap music and don’t want to listen for a few minutes every hour.

Finally, I have some special appreciation for Venere as he very neatly explained terms I’ve seen many times but for which I’ve only been able to find complicated definitions. Thank you, Mr. Venere and for a very clear description of this technology.