Diagram showing the difference between traditional dip-pen nanolithography using liquid ink (left) and thermal dip-pen nanolithography using ink materials that melt (right).

Researchers from the Georgia Institute of Technology and the Naval Research Laboratory, both in the US, have used a heated atomic force microscope (AFM) cantilever tip to deposit molecules of solid ink onto a surface, physicsweb.org said.
The technique, dubbed thermal dip-pen nanolithography (tDPN), has the advantage of being able to control the ink.
"You might want to use the AFM like a phonograph stylus to feel the bumps on a surface, but if you couldn't turn the ink off you'd be leaving a trace of ink as you moved the tip across the surface," said Paul Sheehan of the Naval Research Laboratory.
"With the ability to turn the ink on and off, you can feel the surface without depositing material and then turn the heat on and put material down only where you want it," he said.
To perform the tDPN technique, the team employed a silicon cantilever that contained a resistive heater and had a radius of curvature at its tip of about 100 nanometers. As the ink they used octadecylphosphonic acid (OPA), a material that has a melting point of 99 ¸C and self-assembles into monolayers on mica, stainless steel, aluminum and oxides such as titania and alumina. Sheehan and colleagues coated the cantilever with OPA before heating it to 122 ¸C to melt the ink. Scanning the tip across a mica substrate laid down 98 nanometer-wide lines of OPA.
The scientists were able to stop depositing molecules from the cantilever by turning off the current supply to the resistive heater. That said, it took around two minutes for the deposition process to stop, perhaps because of the low thermal conductivity of the mica substrate.

An Australian scientist claims that men could face extinction within ten million years, ananova.com said.
Professor Jenny Graves, of Australian National University, believes two different species of human could emerge.
The scientist claims an important aspect of male genetic make-up is under threat.
Graves predicted the mammalian Y chromosome would eventually lose its 45 genes, including the SRY gene that releases male hormones.
The chromosome started life 300 million years ago with 1,438 genes, and has already lost 1,393.
Her research, which involved rodents lacking the SRY gene, found that another chromosome took over the task of harboring a gene, which determines sex.
Graves claims that if the same was to happen with people, it could lead to two or more sex determination systems, resulting in two different human species
However, Filatov, of Birmingham University, argued that the Y chromosome would stop breaking down, and that extinction was unlikely.

Astronomers working in Chile think they may have taken the first direct image of a planet circling another star, BBC News Online said.
The star, called 2M1207, is 230 light-years away and is very much smaller and fainter than our own Sun.
Astronomer Christophe Dumas said: "It is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged."
Benjamin Zuckerman, of the University of California, in Los Angeles, added: "If the candidate companion of 2M1207 is really a planet, this would be the first time that a gravitationally bound exoplanet has been imaged around a star or brown dwarf."
And Anne-Marie Lagrange, from the Grenoble Observatory, France, said: "Our discovery represents a first step towards opening a new field in astrophysics: the imaging and spectroscopic study of planetary systems.
"Such studies will enable astronomers to characterize the physical structure and chemical composition of giant and, eventually, terrestrial-like planets."

Giving infants oranges and bananas regularly may halve their risk of developing childhood leukaemia, suggest the results of a new study.
And a diet containing the curry spice turmeric may also be protective--accounting for the differences in childhood leukaemia rates between east and west, New Scientist said.
Children who ate oranges, orange juice or bananas between four to six times a week during their first two years of life had a significantly reduced risk of developing the cancer, revealed the observational study by US researchers.
Previous studies on childhood leukaemia have not examined the effects of the overall diet in this way, focusing more on possible risk foods like cured meats.
"Our study is unique, and we have elucidated a significant protective association with the consumption of oranges, bananas and orange juice," says Marilyn Kwan, an epidemiologist at the University of California, Berkeley.
However, she cautions that without carrying out a randomized controlled trial, it is difficult to predict exactly how protective eating these fruits may be, or to make firm public health recommendations.
But she notes that in her study "there was a 50 percent reduction in risk".

Fossil hunters in China have unearthed what looks like the final resting place of an adult dinosaur with 34 offspring. The unique discovery shows that at least some dinosaurs cared for their young after they hatched out, and suggests that the parental instincts of present-day birds and reptiles such as crocodiles may have a common evolutionary precursor.
In the fossilized group of horned dinosaurs called Psittacosaurus, a fully grown individual is surrounded by 34 youngsters, all huddled within an area of 0.5 square metres. It is almost certainly a family group rather than a happenstance collection of dead dinosaurs, says David Varricchio of Montana State University in Bozeman, part of the team who unearthed the bones in Liaoning, China.
"It does have that 'wow' aspect to it," he told news@nature.com. "It's more likely than not a family. It's hard to imagine [unrelated] whole skeletons being transported to the same place all together."

A woman who stopped dreaming after a stroke is helping researchers unravel the mysteries of sleep, nature.com said.
The 73-year-old patient was admitted to hospital after a stroke disrupted blood flow to an area at the back of her brain, called the occipital lobe.
At first, her symptoms were not unusual--she lost some vision and was weak on one side of the body. But as the initial problems faded a few days later, a new symptom emerged: the woman had stopped dreaming.
She used to experience 3 to 4 dreams per week, says Claudio Bassetti, now of University Hospital Zurich in Switzerland, who studied the woman.
After the stroke, she had no dreams for a whole year, yet her sleep and mental functions appeared otherwise unaffected.
People have been fascinated by dreams for centuries. Psychologist Sigmund Freud believed that dreams offer a release for repressed feelings. Others think they help us empty our minds at the end of a busy day, or solve problems as we sleep.
But the stroke study suggests that humans can live without dreams.