You may have missed – skewering cells, ant wars, writing in water

Science you might have overlooked last week, because it was so tiny.

Micro-spikes skewer superbugs

A new study has shown that rough surfaces, inspired by bacteria-killing spikes on insect wings, may be more effective at combating antimicrobial-resistant bugs than previously thought.

Scientists from RMIT University in Australia designed a pattern of microscale spikes that can be etched onto titanium implants or other surfaces, to provide protection from bacteria and fungus.

Detailed in a paper in the journal Advanced Materials Interfaces, the altered titanium surface is effective at killing multi-drug resistant Candida fungus, which is responsible for 1 in 10 hospital-acquired medical device infections.

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A ruptured Candida fungus cell on top of the micro-spiked titanium surface. Credit: RMIT University

The spikes, which are about the height of a bacterial cell, destroyed about half of the cells soon after contact and rendered the other half unviable – unable to reproduce or cause infection – due to the injuries sustained. They then underwent programmed cell death.

“This latest study suggests that it may not be entirely necessary for all surfaces to eliminate all pathogens immediately upon contact if we can show that the surfaces are causing programmed cell death in the surviving cells, meaning they die regardless,” says Professor Elena Ivanova, group leader and co-author of the study.

Scientists write in water

Not unlike how an aircraft writes in the sky by leaving behind a 3-dimensional vapour trail, scientists have written in water, and written it up in a paper in the journal Small.

“We have put the ink directly in the water and use a microbead of ion-exchange material with a diameter of 20 to 50 [micrometres] as a writing instrument,” says co-author Thomas Palberg, a professor in Johannes Gutenburg University Mainz, Germany.

A selection of images drawn in water
A selection of images drawn in water (linear scales: 250 µm). Credit: ill./©: Thomas Palberg, Benno Liebchen

The bead works by altering the pH of the water as it is rolled across the base of a water bath, which attracts ink particles that accumulate in the path marked out by it. The bead is so small – less than half the diameter of a human hair – that it generates no vortices when it moves in the water.

“In a water bath no bigger than a one Euro coin, we were able to produce a simple house-like pattern in the size of the tittle of an ‘I’ character in an 18 point font, and then viewed this under the microscope. But we are still only in the preliminary phase.” (Tittle is the dot on an “i” or “j”. )

Giving native species a leg up in the ant wars

A new study has used video game simulations and real-world ant battles to show how native Australian ants can be given a fighting chance against aggressive introduced species.

Researchers investigated two ant species. The Australian meat ant, Iridomyrmex purpureus, are large ants found across undisturbed bushland in regional Australia. The second, the invasive Argentine ant, Linepithema humile, are comparatively small but live in extremely large, hyper-cooperative colonies.

A larger ant battles a much smaller one on a white surface
An ant battle between an Australian meat ant, a native species, and a smaller Argentine ant, a notorious pest. Credit: Bruce Webber/CSIRO

“What we found from virtual gaming and then real-life ant battles was that mortality in the small armies of Australian meat ants facing off with large armies of non-native Argentine ants was lower in complex arenas and higher in simple arenas,” says Dr Samuel Lymbery, first author of the study who undertook the work at the University of Western Australia and CSIRO.

The ant battlefield research could have practical application for non-native invasive ant management because it suggests that modify environments by adding natural debris or other structures may favour larger native species.

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Researchers used mathematical models on video game simulations, garnered from Age of Empires II, to illustrate how battlefield dynamics change warfare outcomes for ants.

“Warfare theory suggests that fewer, stronger soldiers will be more effective when battles are a series of one-on-one duels. But larger armies are more effective when they can surround their enemies and concentrate attacks,” Lymbery says.

“Battlefield complexity can tip the balance in favour of one strategy over another.”

The paper has been published in the Proceedings of the National Academy of Sciences.

Tiny robot can squish itself into tight spaces

Engineers have taken inspiration from the insect world to design a small, squishable robot that can passively change its shape to squeeze through narrow gaps.

CLARI, Compliant Legged Articulated Robotic Insect, can transform from square to long and slender when necessary and has four legs – but this could change. The research is published in the journal Advanced Intelligent Systems.

“It has a modular design, which means it’s very easy to customize and add more legs. Eventually, we’d like to build an eight-legged, spider-style robot that could walk over a web,” says co-author Heiko Kabutz, a doctoral student in the Department of Mechanical Engineering at the University of Colorado Boulder in the US.

“When we try to catch an insect, they can disappear into a gap. But if we have robots with the capabilities of a spider or a fly, we can add cameras or sensors, and now we’re able to start exploring spaces we couldn’t get into before.”

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