Worming a way into ‘pleasurable’ endoscopy
Imitating the paddleworm
Endoscopy can be a deeply uncomfortable experience. Improving matters, BIOLOCH researchers are attempting to apply the motion techniques used by lower animal forms to endoscopy technology to develop a prototype capable of ‘pulling’ itself into a patient’s internals, rather than being pushed as it is now.
Having a tube pushed inside you, no matter how small or how sensitively applied, is not a procedure anyone would want to repeat. Plus there is always the risk of tearing delicate internal organs. Not so surprising, therefore, that the potential for a successful alternative could be very high.
The BIOLOCH IST project is using the ragworm or paddleworm, as commonly found on the seashore as their model for an endoscope-type prototype instrument.
“The basic concept is to develop a replacement for the current colonic endoscope, which is quite large and stiff, and has to be pushed inside a patient,” says Paolo Dario, from the Scuola Superiore Sant’Anna of Pisa (Italy). “If you can pull a device rather than push it, you can reduce the bending forces and so lessen the chance of damage to a patient’s internal organs. We looked to nature for a model and chose the paddleworm, because it is capable of ‘swimming’ with ease through relatively soft, unstructured environments.”
BIOLOCH’s first step was to study the locomotion mechanisms used by these animals, which move in wet environments containing large amounts of solid and semi-solid material. Researchers also examined the mechanisms of attachment used by parasites, both internal and external, in order to understand how they gained purchase on soft tissue.
The project’s objective is to understand the motion systems used by such lower animal forms, and to design and fabricate mini- and micro-machines inspired by such biological systems. Such bio-inspired machines have potential applications in many fields where direct human intervention is difficult or dangerous, and remote inspection is required.
The project’s initial prototype consists of a simple worm with a flexible central spine and paddles sticking out either side along the worm’s body. Researchers are now working on a more advanced prototype in which the paddles themselves are capable of moving. To this end the team has had to recruit a biologist to examine how the worms move, and explain these movements to the engineers so that they can work out how to actuate and control the mechanical worm.
Julian Vincent from the University of Bath (UK) explains that paddleworms have a very different way of moving compared to earthworms. The paddleworm’s sine wave locomotion technique runs forward along the body rather than backwards as is the case with the earthworm.
“If you take a wriggly worm with a smooth body, the sine wave moves backwards as the worm moves forwards. But if you put paddles on which stick out to the side of the body, the physics of thrust production changes and the sine wave has to move forwards. The advantage from our point of view is that the paddle worm has a much greater variety of styles of moving, since it can remain straight and just move the paddles, wriggle and keep the paddles still, or wriggle and move the paddles as well. This gives more versatility in speed and general control. The paddle worm can also build burrows very rapidly. So the chances are that a robotic motor based on this design will be more versatile and faster than most others.’
Making endoscopy pleasurable!
At the moment the prototypes are rather slow. Current medical procedure for endoscopies allows around only 10 minutes to reach the end of the colon. Says Dario, “Our worm takes about thirty minutes to cover a comparable distance, so it needs to be speeded up by a factor of ten to fifty. However if we can get the paddles to move as well as the central spine, this should double the energy delivered during the power stroke, so we aim to improve the speed by a factor of ten.”
An early prototype of the BIOLOCH worm is already on display at an exhibition on biomimetics at the Zoological Museum in Copenhagen, Denmark, which continues until early 2005. However, the BIOLOCH team intend to have the second, more advanced prototype, which will have a smaller diameter and be more flexible, ready and working by the end of the project in mid-2005.
“Ultimately”, says Vincent, “our idea is to turn the current ordeal of the colonic endoscopy procedure into something akin to a pleasurable experience!”
Tara Morris | alfa