Building a Better Laparoscope – with Dragonflies

One of the great breakthroughs in modern medicine – laparoscopic surgery – is on the verge of getting even better, with the help of some dragonflies.

Laparoscopic surgery, often referred to as minimally invasive surgery, is the technique whereby a long fiber optic cable is used to deliver a camera deep within the body. The tiny camera provides the surgeon with the pictures needed for her to perform the work, utilizing equally tiny surgical instruments.

But the problem with most camera lenses is that they are modeled after human eyes, with all the limitations of human vision. Now, a team of bioengineers at University of California, Berkeley, has created a series of artificial compound eyes using the eyes of insects such as dragonflies and houseflies as models.

These eyes can eventually be used as cameras or sensory detectors to capture visual or chemical information from a wider field of vision than previously possible, even with the best fish-eye lens, said Luke P. Lee, the team's principal investigator. Potential applications include surveillance; high-speed motion detection; environmental sensing; medical procedures, such as endoscopies and image-guided surgeries, that require cameras; and a number of clinical treatments that can be controlled by implanted light delivery devices.

They are the first hemispherical, three-dimensional optical systems to integrate microlens arrays. These are thousands of tiny lenses packed side by side with self-aligned, self-written waveguides, or light-conducting channels that themselves have been created by beams of light, said Lee.

What he and his team came up with is a low-cost, easy-to-replicate method of creating pinhead-sized polymer resin domes spiked with thousands of light-guiding channels, each topped with its own lens. Not only are these units packed together in the same hexagonal, honeycomb pattern as in an insect's compound eye, but each is also remarkably similar in size, design, shape and function to an ommatidium, the individual sensory unit of a compound eye.

Just like pins in a pincushion - or a dragonfly's 30,000 ommatidia - the team's artificial ommatidia are each oriented at a slightly different angle. Lee's team has shown that the lenses and waveguides of the artificial eyes focus and conduct light in the same way as an insect's eye.

While an insect's ommatidia each end in a photoreceptor cell that transmits a light signal to the creature's optic nerve, Lee plans to couple his team's ommatidia with CCD photodiodes, the light-capturing units used in digital cameras and camcorders. He also has plans to link them to spectroscopes for chemical detection and analysis.