New process makes nanofibers in complex shapes and unlimited lengths

The continuous fabrication of complex, three-dimensional nanoscale structures and the ability to grow individual nanowires of unlimited length are now possible with a process developed by researchers at the University of Illinois.

Based on the rapid evaporation of solvent from simple “inks,” the process has been used to fabricate freestanding nanofibers, stacked arrays of nanofibers and continuously wound spools of nanowires. Potential applications include electronic interconnects, biocompatible scaffolds and nanofluidic networks.

“The process is like drawing with a fountain pen – the ink comes out and quickly dries or ‘solidifies,’ ” said Min-Feng Yu, a professor of mechanical science and engineering, and an affiliate of the Beckman Institute. “But, unlike drawing with a fountain pen, we can draw objects in three dimensions.”

Yu and graduate students Abhijit Suryavanshi and Jie Hu describe the drawing process in a paper accepted for publication in the journal Advanced Materials, and posted on its Web site.

To use the new process, the researchers begin with a reservoir of ink connected to a glass micropipette that has an aperture as small as 100 nanometers. The micropipette is brought close to a substrate until a liquid meniscus forms between the two. As the micropipette is then smoothly pulled away, ink is drawn from the reservoir. Within the tiny meniscus, the solute nucleates and precipitates as the solvent quickly evaporates.

So far, the scientists have fabricated freestanding nanofibers approximately 25 nanometers in diameter and 20 microns long, and straight nanofibers approximately 100 nanometers in diameter and 16 millimeters long (limited only by the travel range of the device that moves the micropipette).

To draw longer nanowires, the researchers developed a precision spinning process that simultaneously draws and winds a nanofiber on a spool that is millimeters in diameter. Using this technique, Yu and his students wound a coil of microfiber. The microfiber was approximately 850 nanometers in diameter and 40 centimeters long.

To further demonstrate the versatility of the drawing process, for which the U. of I. has applied for a patent, the researchers drew nanofibers out of sugar, out of potassium hydroxide (a major industrial chemical) and out of densely packed quantum dots. While the nanofibers are currently fabricated from water-based inks, the process is readily extendable to inks made with volatile organic solvents, Yu said.

“Our procedure offers an economically viable alternative for the direct-write manufacture of nanofibers made from many materials,” Yu said. “In addition, the process can be used to integrate nanoscale and microscale components.”

New research shows that iPods do not interfere with cardiac pacemakers

A report in the open access journal BioMedical Engineering OnLine refutes claims that portable music players, such as Apple's iPod, interfere with cardiac pacemakers.

Howard Bassen, a researcher with the U.S. Food and Drug Administration in Rockville, Md., led a research team that measured the magnetic fields produced by four different iPod models: a fourth-generation iPod and an iPod with video, and an iPod nano and iPod shuffle. They also measured the voltages delivered inside the pacemaker by the magnetic fields from the iPods. All measurements indicated there would be no effects on users with cardiac pacemakers.

Over the past year, a spate of media reports speculated on iPod interference with cardiac pacemakers. These reports, however, were based on a single incident where a patient with a cardiac pacemaker suffered dizziness while using an iPod. Cardiologists operated an iPod during the patient’s examination, and noted interference with the pacemaker.

The cardiologists published their results in the medical journal, Heart Rhythm.

After publication, there was talk of warning labels for portable music and video players, although a subsequent clinical study failed to show any dangerous connection between the music devices and patients with pacemakers.

Now, Bassen’s more detailed study demonstrates that iPods are not capable of producing electromagnetic interference in implanted pacemakers.

Using a 3-coil sensor, the team measured the magnetic field produced by the iPod at a distance of around 5 to 10 millimeters. They obtained readings for the magnetic field at various specific and small regions 10 mm from an iPod. The peak magnetic field strength was 0.2 millionths of a Tesla, a value hundreds of times lower than the levels capable of interfering with a pacemaker.

In addition, Bassen’s team attempted to detect any voltages these fields might produce within the protective "can" of a pacemaker. The can was placed inside a simulated human torso used by pacemaker manufacturers for interference testing. Bassen and his team found that the voltage levels within the pacemaker can were well below the detection limits of their highly sensitive equipment.

"Based on the observations of our in-vitro study we conclude that no interference effects can occur in pacemakers exposed to the iPods we tested," Bassen concluded.

Prostate cancer: Watchful wait or vaccinate?

Researchers have developed a prostate cancer vaccine that prevented the development of cancer in 90 percent of young mice genetically predestined to develop the disease. In the February 1 issue of Cancer Research, they suggest the same strategy might work for men with rising levels of PSA (prostate specific antigen), a potential diagnostic indicator of prostate cancer.

“By early vaccination, we have basically given these mice life-long protection against a disease they were destined to have,” said the study’s lead investigator, W. Martin Kast, Ph.D., a professor of Molecular Microbiology & Immunology and Obstetrics & Gynecology at the Norris Comprehensive Cancer Center. “This has never been done before and, with further research, could represent a paradigm shift in the management of human prostate cancer.”

Now, men with rising PSA levels but no other signs of cancer are advised “watchful waiting” – no treatment until signs of the cancer appear, Kast says. “But what if instead of a watchful wait, we vaccinate" That could change the course of the disease.”

The study findings also represent a new way to think about the use of therapeutic prostate cancer vaccines, Kast says. Vaccines now in testing are designed to treat men whose cancers are advanced and unresponsive to therapy, and results have offered limited clinical benefit, he says. This novel approach targets the precancerous state with the aim of preventing cancer from developing, he says.

The Kast team’s preventive vaccine is designed to mount an immune response against prostate stem cell antigen (PSCA), the protein target of some therapeutic vaccines under development. PSCA, a membrane protein, is over-expressed in about one-third of early-stage prostate cancers, but expression ramps up in all prostate tumors as they grow and advance. PSCA is also expressed at low-levels in normal prostate gland tissue as well as in the bladder, colon, kidney and stomach.

The researchers created a prime-boost vaccination scheme using two kinds of vaccines and tested it in 8-week-old mice that were genetically altered to develop prostate cancer later in life. The first vaccine simply delivered a fragment of DNA that coded for PSCA, thus producing an influx of PSCA protein to alert the immune system. The booster shot, given two weeks later, used a modified horse virus to deliver the PSCA gene.

“Confronting the immune system in two different ways forces it to mount a strong response,” Kast said.

In the experimental group, two of 20 mice developed prostate cancer at the end of one year, and by contrast, all control mice had died of the disease. Researchers found that mice in the experimental group had all developed very small tumors that did not progress. “There were tiny nodules of prostate cancer in the mice that were surrounded by an army of immune system cells,” Kast said. “The vaccination turned the cancer into a chronic, manageable disease.”

The vaccination strategy also works with other antigens, Kast says. The researchers recently tried another prostate cancer membrane target and found that after 1.5 years, 65 percent of experimental mice were still alive, and of those that died, the suspected cause was old age.

Crucially, investigators further found that treated mice did not develop autoimmune disease, a side effect that could develop if the vaccine had also targeted PSCA expression in normal cells. “Theoretically, the vaccine could produce a response in any tissue that expresses the antigen, but the fact that PSCA is expressed in such low levels in normal tissue may prevent that complication,” he said.

Still, studies in humans are needed to ensure autoimmunity does not develop, Kast says.

“We feel this is a very promising approach,” he said. “With just two shots, the vaccine will prime immune cells to be on the lookout for any cell that over-expresses PSCA.”

UW paper in Science shows how some solids mimic liquids on nanoscale

A University of Waterloo physics and astronomy research team, in a paper to be published Friday in Science Magazine, shows how some solids behave like liquids on the nanoscale.

The UW researchers, professor James Forrest and then-graduate student Zahra Fakhraai, take a major step forward in discovering how to measure polymer substances using nanoscale technology.

They explore the properties of the large class of natural and synthetic materials on the nanoscale. Their work, appearing in the Feb. 1 issue of the prestigious international journal of original research, is entitled Measuring the Surface Dynamics of Glassy Polymers.

Nanoscale technology involves techniques used to manipulate matter at the scale of atoms and molecules. A nanometre (nm) equals one billionth of a metre. In comparison, one human hair is about 80,000 nm thick.

"We are examining the question of what are the properties of materials on the nanoscale," says Forrest, an expert on the physics of soft materials and polymer thin films. "As technology pushes further and further into the nano domain, this question becomes increasingly important."

In other words, scientists know the bulk properties of materials, such as gold or polystyrene (a strong plastic used to make Styrofoam). But it does not mean that if they measure a nanometre-sized sample, or examine with a technique capable of nanometre resolution, they will see the same thing.

The UW paper explores the first few nanometres of a polystyrene surface. The researchers have developed a technique to look at the dynamical properties of this near surface region with nanometre resolution.

They found that even when the bulk of the material becomes solid, the surface behaves essentially liquid-like. This discovery has huge implications in polymer processing or in any application (such as nanolithography), where very thin polymer films are used.

"The cute thing about the technique is that the actual ideas behind it are almost 500 years old, and even though this has been an outstanding problem and studied in detail for over a decade without resolution, no one had yet thought of this very simple experiment," Forrest says.

Swarm approach to photography

A new approach to cleaning up digital photos and other images has been developed by researchers in the UK and Jordan. The research, published recently in Inderscience's International Journal of Innovative Computing and Applications uses a computer algorithm known as a PSO (Particle Swarm Optimization) to intelligently boost contrast and detail in an image without distorting the underlying features.

Malik Braik and Alaa Sheta of the Department of Information Technology, at Al-Balqa Applied University, in Salt, Jordan, working with Aladdin Ayesh in the Division of Computer Engineering, at De Montfort University, Leicester, UK, explain that the Particle Swarm Optimization (PSO) algorithm represents an entirely new approach to solving all kinds of optimization problems. PSO has recently been used in computer science and electrical engineering.

The roots of the PSO algorithms lie in Swarm Intelligence paradigm which is inspired by models of living systems, artificial life (A-life) in general, and by theories of how and why birds flock, why schools of fish behave the way they do and in particular what controls swarming insects. Despite its potential it relies on only simple mathematics and does not need powerful computers to run, which means software applications based on PSO would not be limited only to academic researchers and those with access to supercomputers.

There have been several approaches to image enhancement developed by image manipulation software companies and others. However, none comes up to the standards of the kind of image enhancement often seen in fiction, where a blurry distorted image on a screen is rendered pin-sharp at the click of a mouse. PSO, however, takes image enhancement a step closer to this ideal.

PSO is based on a mathematical model of the social interactions of swarms. The algorithm treats each version of an image as an individual member of the swarm and makes a single, small adjustment to contrast levels, edge sharpness, and other image parameters. The algorithm then determines whether the new members of the swarm are better or worse than the original according to an objective fitness criterion.

"The objective of the algorithm is to maximize the total number of pixels in the edges, thus being able to visualize more details in the images," explain the researchers. Such enhancement might be useful in improving snapshots of CCTV quality for identification of individuals or vehicle number plates, it might also have application in improving images produced with lower quality cameras, such as camera phones, that are required for use in publishing or TV where image quality standards are usually higher.

The process of enhancing step by step is repeated to create a swarm of images in computer memory which have been graded relative to each other, the fittest end up at the front of the swarm until a single individual that is the most effectively enhanced.

"The obtained results using grey scale images indicate that PSO is better than other approaches in terms of the computational time and both the objective evaluation and maximization of the number of pixels in the edges of the tested images," they add.

Mikropkaya yaşamın en eski kanıtı

Paris’teki Küresel Fizik Enstitüsü mensuplarının İngiliz Nature Geoscience dergisinde yayınladıkları araştırmada, Avustralya’daki fosilleşmiş canlı kalıntılarından oluşan ve “stromatolit” adı verilen kayalar üzerinde yapılan keşfin, mikropların bu eski kaya oluşumlarındaki “aracılığının resmi kanıtı” olduğu belirtildi.
Avustralyalı ve Kanadalı bilim adamları da 2006’da, 3,4 milyar yaşında stromatolitler keşfetmiş ve bunların kökenlerinin mikroplara değgin olduğu sonucuna ulaşmışlardı. Stromatolitler, bakterilerin çıkardığı karbondioksitle çamur tortularının katmanlaşarak birikmesiyle oluşuyor.

Fransız araştırmacıların bilimsel makalelerine göre, bilim dünyasının büyük bölümü, son yıllarda yapılan araştırmalar ışığında, stromatolit fosillerin, bugünkü çevresel koşullarda olduğu gibi, “fotosentetik mikroorganizmaların faaliyeti” sonucu oluştuklarını düşünüyor.

Araştırmacılar, Avustralya’nın Tumbiana bölgesindeki kayalarda, “aragon nanokristalleri içeren organik minik kabarcıklar” keşfettiklerini ve bunları analiz ettiklerini belirterek, bugünkü bakterilerin kökeninin, mikroorganizmaların ölümünden sonra çabucak kalsite dönüşen, son derece değişken kalsiyum karbonatın çokbiçimli hali olan aragonit çökeltisi olduğuna dikkat çektiler.

Bilim çevreleri, Dünya üzerindeki ilk yaşam belirtisinin ve bunun biçiminin tarihlendirilmesinin, Mars gibi diğer gezegenlerdeki olası yaşam izlerinin araştırılması için özellikle önemli olduğuna işaret ediyor.