Castor oil may take on new duties
A new way to seal plastic casings may bring medical nanotechnology closer to real use.
Columbus, Ohio—A new way to seal plastic casings may bring medical nanotechnology closer to real use, as Ohio State University (OSU) engineers found a new way to manufacture the small devices.
The Buckeye researchers found their technique helps the flow of medicine and other fluids through such devices and even alters the material on the surface of a device to suit medical applications.
“Plastics have great potential for use in these devices because they are inexpensive and easy to shape into individual parts, but sealing a tiny casing poses a special challenge,” said L. James Lee, a professor of chemical engineering at OSU. “So does altering the characteristics of the plastic to suit different medical tasks. Our method allows someone to do both in one shot.”
One day these devices could deliver medicine directly to tumors or other sites of disease in the body.
Lee’s team investigated several techniques for sealing such devices, including welding, gluing, and even sticking parts together with double-sided adhesive tape. Gluing seemed the most promising, but traditional adhesives only gummed up the tiny channels found in microdevices.
Then the team hit on a method for using traditional liquid adhesive in a nontraditional way.
For this initial work, Lee and his colleagues molded a plastic device about the size of a small matchstick. The device consisted of a 100-micrometer-wide channel, about as wide as a human hair, with a fluid reservoir at each end.
They molded the device in two pieces: a bottom platform containing the channel and reservoirs, and a lid. They coated both parts with a few drops of a commercially available adhesive called hydroxyethyl methacrylate (HEMA) and fit the two together.
HEMA is a bonding agent for dental appliances. While sticky in its liquid form, HEMA cures to a smooth surface under ultraviolet (UV) light, like exposed glue on a model airplane.
After coating and filling the device with HEMA, the researchers blew a short burst of nitrogen gas in one end of the device and out the other, forcing the adhesive to coat the inner surfaces on its way out. Finally, they cured the entire device under UV light.
Tests revealed that liquid traveled successfully through the tiny channel between the two reservoirs with no leaks, so the device appeared to be sealed successfully inside and outside.
With an electron microscope, the researchers saw most of the HEMA had flowed cleanly throughout the device, but some remained in the corners of the reservoirs. As a result, the sharp corners were smoothed out, which promotes good fluid flow, Lee said.
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