Insect Biomechanics and Robotics

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The ways insects move is of great interest to scientists. Cockroaches for example have the ability to navigate very rough terrain effortlessly. It’s no surprise then that we seek to emulate the mechanics of insects such as this, and in recent years especially, implement them in robots.

Walking/Running

The six legs of an insect provide it with dynamic stability. Essentially, an insect has two pairs of “tripods” that it uses to walk. While one set is moving forward (let’s call it the right front, right back, and left middle), the other set it remaining stationary and supporting the insect (the right middle, left front, and left back).

Left a sketch of a cockroach with the legs forming one of the tripods colored either red or blue. On the right a phase diagram for slow walking, each mark represents the swing phase - when that leg is up in the air.

Cockroach tripod mechanism of walking. Source: Marianne Alleyne

This dynamic stability also allows the cockroach to run very fast over rough terrain. However, this is based purely on mechanical feedback, as its legs are moving too fast for neural feedback to play a role. Careful study has found that insects that are able to traverse uneven terrain all possess hairy setae on their legs which allow them to use their entire leg as a sort of distributed foot. This is in contrast to the smooth legs of an animal such as a crab, which is unable to navigate uneven terrain efficiently.

Jumping

Insects also have a variety of mechanisms of jumping. The click beetle is able to flex its head and snap it back to launch its body into the air. This legless method of jumping, however, doesn’t allow for precise landings.

Springtails have, as the name implies, a “spring tail” that folds under their body and can then be used to launch themselves upwards.

The springing mechanism of a generalized springtail; partially retracted (left) and extended (right).

Jumping mechanism of springtail. Source: Marianne Alleyne at InsectsDidItFirst.com

Trap-jaw ants are able to use their powerful mandibles to generate a force large enough to launch their entire body into the air:

Diagram of Trap-jaw ant mandibles. Source: Wikimedia Commons

And finally, locusts and grasshoppers are able to jump using their powerful hindlegs to store up energy and then explosively release it:

Jumping Grasshopper. Source: Michael Durham, via Flickr

Of course these are only a few of the mechanisms insects have for jumping. Many are not well understood and are still the subject of intense study.

Burrowing

Digging and burrowing in insects is not currently well understood. What we do know, is that certain insects such as the mole cricket have special appendages that seem to be especially suited to these activities. The mechanism through which they do so definitely requires further study, in my opinion.

European Mole Cricket. Source: Flickr

Aquatic Locomotion

It should come as no surprise by this point that insects have numerous methods through which they can navigate through water. Some examples include water boatmen with their setae-lined, paddle-like arms; damselfly nymphs, which use their tails as paddles; and dragonfly nymphs, which are able to bring water in through their rectum and explosively propel it when they need to move (yes, you read that right!).

One insect that interests me in particular (and will likely be the subject of a future blog post) is the water strider. These fascinating creatures are able to create vortices in the surrounding water which pull them forward.

Sources:

https://learn.illinois.edu/mod/lesson/view.php?id=195346

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