Imaging C. elegans worms has proved useful for monitoring laser microsurgery and for studying gene expression tied to fluorescent labels, yet it can be difficult -- if not impossible -- to image the wriggling creatures. Conventional methods for immobilizing them include gluing them to a substrate and using a drug that paralyzes them. However, paralytic drugs can change the biochemical state of the worms, and gluing them one by one takes a substantial amount of time. Also, the glue may introduce some toxicity, and the worms cannot be unglued safely.Researchers developed a microfluidic device that rapidly immobilizes more than 100 C. elegans worms for imaging. The worms are vacuum-suctioned through channels with tapered ends that trap them. Reprinted with permission of Lab on a Chip.To immobilize C. elegans for imaging, researchers from Harvard University in Cambridge, Mass., and from Harvard Medical School in Boston have developed a microfluidic device that can trap more than 100 worms in less than 15 minutes, more than an order of magnitude faster than the gluing method. The technique consists of an array of 128 channels that have tapered ends. As a vacuum sucks the worms toward the ends, they become wedged there. The researchers used a syringe to push them out of the device.In a test of the system, detailed in the November issue of Lab on a Chip, the researchers found that 116 of 128 worms were trapped, or that more than 90 percent of the channels contained one worm. Channels rarely trapped more than a single worm. High-magnification microscopy showed detailed anatomical features such as the mouth, pharynx, developing embryos and egg cells. Once pushed out of the device, the worms remained healthy and could still reproduce robustly. The researchers said that it is possible to expand the device to trap greater numbers of C. elegans.