Scientists are constantly borrowing from nature to make materials with new properties. The latest, inspired by the carnivorous pitcher plant Nepenthes, is the most slippery surface ever made.
Insects are attracted to Nepenthes by its smell but when they try to settle or walk on it, they cannot get a grip, so they slide to their doom in the plant’s digestive juices at the bottom of the pitcher.
Researchers at Harvard University investigated and copied the super-slippery chemistry of Nepenthes to create a material that repels any type of liquid, from water-based solutions to oils and organic compounds.
They expect the technology to find applications in biomedical fluid handling, fuel transport, and anti-fouling and anti-icing technologies. It could even lead to self-cleaning windows and improved optical devices.
“Inspired by the pitcher plant, we developed a new coating that outperforms its natural and synthetic counterparts and provides a simple and versatile solution for liquid and solid repellency,” says lead author Joanna Aizenberg.
Until now the best liquid-repelling, bio-inspired surfaces have been based on another plant, the lotus, whose leaves are brilliant at resisting water but not so effective at throwing off organic liquids.
Unlike lotus leaves, which have a micro-textured, water-repellent surface, the pitcher plant locks a layer of lubricating fluid on to its surface. This water-based fluid becomes the repellent surface. The researchers made their synthetic version – known as slippery liquid-infused porous surface (Slips) – by infusing a nanostructured porous material with a lubricating fluid.
“The effect is similar to when a car hydroplanes, the tires gliding on the water rather than the road,” says Tak-Sing Wong, another member of the Harvard team. “In the case of the unlucky ants, the oil on the bottom of their feet will not stick to the slippery coating on the plant.”
“The repellent fluid surface offers additional benefits, as it is intrinsically smooth and free of defects,” adds Wong. “Even after we damage a sample by scraping it with a knife or blade, the surface repairs itself almost instantaneously and the repellent qualities remain, making Slips self-healing.”
In addition, the almost frictionless effect persists under extreme conditions: high pressure (up to 675 atmospheres) and humidity, and in very low temperatures. When the team conducted studies outside after a snowstorm, their synthetic material withstood the cold and even repelled ice.
But it is not heat-proof. In its present form Slips cannot replace Teflon in non-stick pots and pans.
The importance of DNA’s dark matter
Genomic analysis over the past decade has shown that only 2 per cent of human DNA consists of traditional “genes”, coding for the proteins which do most of the work in the human body. The identity of the remaining 98 per cent remains largely mysterious, though it is clear that some of this “non-coding” DNA performs important switching and regulatory roles. Scientists no longer dismiss it as “junk DNA”.
Alasdair MacKenzie of Aberdeen University, who has spent the past 10 years investigating the “dark matter” of the genome, believes it plays a role in disease – and offers a new approach to drug discovery.
His research focuses on galanin, a neuropeptide (small brain protein) which among other things influences appetite and food preferences.
By comparing the human genome with other species, MacKenzie found a piece of DNA called Gal 5.1 that turns out to be a genetic switch, controlling galanin production in the brain’s hypothalamus. His team went on to discover mutations in Gal 5.1 that affect its switching ability and therefore the amount of galanin produced.
Different human populations have different proportions of the “weak” and “strong” galanin switch, which may be partly responsible for different attitudes to food and drink around the world.
These switches could be manipulated with drugs. “It’s at a very early stage, but this shows the possibility of using this to develop therapies,” MacKenzie told the recent British Science Festival in Bradford. “We are starting to get a handle on how to modulate the switches.”
MacKenzie has also uncovered switches controlling brain-derived neurotrophic factor (BDNF), a protein involved in long-term memory which has been implicated in depression and age-related cognitive decline.
Problem-solving on the wing
The more the merrier is the rule when it comes to avian problem-solving. Observations of wild blue tits and great tits show that larger flocks are better at working out how to obtain seeds from a feeder that will only dispense when levers are pulled in a particular way.
Oxford University scientists, who carried out the study in Wytham Woods, believe this is probably because the larger the group, the better the chance of it including a bright or experienced bird that can solve a particular new problem.
“Previous research has suggested that this effect, sometimes called the ‘pool of competence’, occurs in humans, but this is the first direct evidence that a similar effect occurs in non-human animals,” says Julie Morand-Ferron, leader of the study published in Proceedings of the National Academy of Sciences.
“Surprisingly, we found that there does not seem to be an optimal size of flock after which the benefits of birds ‘putting their heads together’ tails off,” she adds. “Instead, for these social songbirds, 30 heads are almost always better than 20, and 20 better than 10.”
As the size of the groups grew, individual birds got more food on average in return for the time they spent puzzling how to work the seed dispensers.
By comparing behaviour at exposed locations with those with cover, researchers concluded that larger groups also have more eyes to watch out for predators while individuals complete a task.
Coeducation versus single-sex schooling
Claims that single-sex schools improve academic performance are not supported by valid evidence, according to a hard-hitting paper, “The Pseudoscience of Single-Sex Schooling”, in Science, the leading US research journal.
The paper, written by a group of American educational psychologists committed to coeducational schooling, concludes that evidence to support the academic superiority of separate boys and girls schools is anecdotal at best.
Sex-segregated teaching – traditionally the preserve of private schools in the US as in the UK – is now moving into the American public sector, where there are more than 500 single-sex classrooms. This development is “deeply misguided, and often justified by weak, cherry-picked, or misconstrued scientific claims rather than by valid scientific evidence,” the authors say.
They argue that although there are many excellent single-sex schools, their quality is a result of good student recruitment, a strong curriculum and other factors that promote achievement just as well in coeducational schools.
While some supporters of single-sex schools claim that boys and girls learn differently, and therefore benefit from different teaching styles, the paper maintains that the few differences between male and female brains are not linked to learning.
But the authors say there is evidence for negative consequences of segregating by sex: that it increases gender divisions among children and strengthens sexist attitudes.
The north-south orientation of the American continents meant that people and technology spread more slowly there than in Eurasia, which has a mainly east-west orientation, according to new US research.