Efficient killer (Image: Ryan McVay/Stone/Getty)

ROBOTS that mimic the Venus flytrap could run on live insects and spiders, snatching and digesting them for fuel. Now two prototypes have been developed that employ smart materials to rapidly ensnare their prey.

Venus flytraps (Dionaea muscipula) catch insects using two specially adapted leaves. When a bug lands it brushes tiny hairs on the surface, triggering the trapping mechanism. The leaves snap shut in a mere 100 milliseconds, and the plant kills and digests its quarry (see diagram).

Recreating this method means finding materials that can not only detect the presence of an insect but also close on it quickly. At Seoul National University in South Korea, Seung-Won Kim and colleagues have done this using shape memory materials. These switch between two stable shapes when subjected to force, heat or an electric current.


The team used two different materials – a clamshell-shaped piece of carbon fibre that acts as the leaves, connected by a shape-memory metal spring. The weight of an insect on the spring makes it contract sharply, pulling the leaves together and enveloping the prey. Opening the trap once more is just a matter of applying a current to the spring.

Mohsen Shahinpoor at the University of Maine in Orono took a different approach. His robot flytrap uses artificial muscles made of polymer membranes coated with gold electrodes. A current travelling through the membrane makes it bend in one direction – and when the polarity is reversed it moves the other way.

Bending the material also produces a voltage, which Shahinpoor has utilised to create sensors. When a bug lands, the tiny voltage it generates triggers a larger power source to apply opposite charges to the leaves, making them attract one another and closing the trap (Bioinspiration and Biomimetics, DOI: 10.1088/1748-3182/6/4/046004).

When a bug lands, the tiny voltage it generates triggers a larger power source to close the trap

“We should be able to benefit enormously from these flytrap technologies,” says Ioannis Ieropoulos of the Bristol Robotics Lab in the UK. He and colleagues previously developed Ecobot, a robot that can digest insects, food scraps and sewage to power itself. Ecobot uses bacteria to break down a fly’s exoskeleton in a reaction that liberates electrons into a circuit, generating electricity.

But without a way to catch prey, the researchers either manually feed Ecobot with dead flies or use an ultraviolet bug lure – like those used in restaurants. That’s no good for an autonomous robot, though. What’s more, UV lures need to be on all the time, wasting precious power, says Ieropoulos. “We’d be happy to talk to these groups about their flytraps.”