Spermbots could one day revolutionise fertility treatments and the delivery of drugs around the human body.

And now a breakthrough has been made that could boost the technology's performance and efficiency.

Researchers have discovered that by shortening the bots and 'feeding' them caffeine they can increase the speed of the biobots by almost a third.

To test the performance of so-called spermbots - robots powered by bovine sperm - researchers more than halved the size of the nanotubes carrying the sperm and added caffeine to the solution they were travelling in. They found that caffeine increased speed by 30% - but the boost only lasted a minute and a half (pictured)

This would mean drugs could be delivered faster and fertility treatments could be sped up, for example.

The first of these biological robots powered by sperm were created by Oliver Schmidt at the Institute for Integrative Nanosciences in Dresden and later developed by Veronika Magdanz at the Leibniz Institute for Solid State and Materials Research in Germany.

Professor Schmidt and his colleagues managed to trap single sperm cells inside metal nanotubes.

To trap the sperm and stop them from escaping, the tubes are narrower at one end.

RISE OF THE SPERMBOTS In December 2013 the first ever biological robots powered by sperm were created by scientists in Germany. Researchers managed to trap single sperm cells inside metal nanotubes and remotely control their direction using magnets. These biobots could be used in humans to deliver drugs to a very specific parts of the body or to help fertilise an egg. Oliver Schmidt at the Institute for Integrative Nanosciences in Dresden created magnetic nanotubes that were 50 microns long by 5 to 8 microns in diameter and dropped these into a fluid containing bull sperm. To trap the sperm and stop them from escaping, the tubes were narrower at one end and could be moved using a magnetic field, Professor Schmidt told MailOnline. In June last year scientists from the Netherlands created cyborg sperm dubbed ‘MagnetoSperm’ that were controlled by fridge magnets. The bots were designed with a metal-coated head and a bendable body that is around six times longer than human sperm. Advertisement

These nanotubes are 50 microns (µm) long by 5 to 8 microns in diameter and are dropped into a fluid containing bull sperm.

They are also magnetic and in June 2014, researchers at the University of Twente in the Netherlands and German University in Cairo were able to steer these robot by directing magnetic field lines.

These bots, dubbed MagnetoSperm, can move up to 0.5 body lengths per second, while a human sperm can cover several times its body length in that time.

More recently, Ms Magdanz and her colleagues tested three techniques for boosting the performance and efficient of such bots.

These techniques are detailed in the paper How to Improve Spermbot Performance.

The first involved shortening the microtubes from 50µm to 20 µm long, in the second test the researchers added a protein called fibronectin (Fn) to the sperm, which binds to cell membranes.

And thirdly, they added caffeine to the solution of moving spermbots.

All of these methods improved the performance of the spermbots, resulting in both higher speeds of the spermbot and higher coupling efficiency between the microtube and the free sperm cells.

When the nanotubes were shortened, the average spermbot velocity rose from 10.4 μm/s up to 33.3 μm/s.

The first of these biological robots powered by sperm were created by Oliver Schmidt at the Institute for Integrative Nanosciences in Dresden (pictured). These nanotubes are 50 microns (µm) long by 5 to 8 microns in diameter and are dropped into a fluid containing bull sperm

In the recent tests, when the nanotubes were shortened, the average velocity rose from 10.4 μm/s up to 33.3 μm/s. This was slower than the so-called free cell, but the speed difference was reduced 16.5 per cent when the tubes were 20 µm long (top left) compared to 81.7 per cent for the 50 μm spermbot (top right)

This was still slower than the so-called free cell travelling on its own, but the speed difference was reduced by 16.5 per cent when the tubes were 20 µm long compared to 81.7 per cent for the 50 μm spermbot.

HOW CAFFEINE AFFECTS SPERM Caffeine is known to increase sperm motility because it causes hyperactivity. It increases calcium levels in the cell by opening calcium channels in the plasma membrane. This raised level causes the sperm to become hyperactive and giving it enough power to penetrate the egg and reach the oocyte for fertilisation. Advertisement

Adding fibronectin to the tubes increased how efficiently the sperm coupled, or connected, with the nanotubes by up to 1.1 per cent in the 20 µm tubes compared to 23.6 per cent rise in the 50 µm versions.

The researchers believe the 50 µm tubes are more efficient due to the larger surface area created for the sperm to 'couple' to.

And when caffeine was added to the solution, the velocity increased by a third around a minute and a half after the caffeine was added.

The team said this increased the speed of the sperm by 30 per cent, on average.

Caffeine is known to increase sperm motility because it causes hyperactivity.

It increases calcium levels in the cell by opening calcium channels in the plasma membrane and these raised levels cause the sperm to become hyperactive, penetrate the egg and reach the oocyte for fertilisation.

Caffeine is known to increase sperm motility because it causes hyperactivity. In June last year scientists created cyborg sperm dubbed ‘MagnetoSperm’ (pictured) that can be controlled by magnets. The bots were designed with a metal-coated head and a bendable body around six times longer than human sperm

Biological robots - or biobots - could be used in humans to deliver drugs to a very specific parts of the body or to help fertilise an egg. MagnetoSperm being controlled using a magnet are pictured

'With the presented methods we achieve an increase of the average spermbot velocity to 33.3 μm and an increase of coupling efficiency to 58.7 per cent, explained the researchers.

'Even if this article describes substantial improvements in spermbot performance, the spermbot design could be enhanced further to optimize sperm cell motion inside the trapping microstructure.

'Furthermore, the coupling still relies on random events and is not controlled. It will be helpful to develop a method that attaches previously selected single sperm cells to the microtubes in a controlled manner.