Air Force engineers need to attach temporary test packages to the outsides of planes during tests, but they do not want to drill any holes that could damage the crafts' structures. So they turned to Michael Gilbert, a polymer scientist at EIC Laboratories in Norwood, Massachusetts, for a solution: an adhesive that comes unstuck at the flick of a switch.
The new glue, called ElectRelease, resembles a standard industrial epoxy, but Gilbert and his colleague Stuart Cogan modified the composition so that it conducts ions (electrically charged atoms). When sandwiched between two pieces of metal, it holds indefinitely until it is exposed to an electric jolt. About 10 to 50 volts of DC current causes the epoxy to debond and become unstuck in about one second to one minute, depending on the temperature. In experiments with the Air Force planes, attachments pulled right off without marring the paint. Other potential aerospace applications for the novel adhesive may include holding a satellite's solar panels in place during launch, then allowing them to unhitch smoothly once the craft is in orbit. At present, many satellites rely on relatively heavy mechanisms to carry out this procedure. Biologists might also benefit from an on-off glue to affix temporary markers or radio tags onto marine animals in order to track their movements.
A 0.5-square-inch layer of ElectRelease glue can hold up this 650-pound I-beam, then unstick in about two seconds.Photograph courtesy of EIC Laboratories (2).