As expected, when they made chains with short (about 500 base pairs) DNA bridges, the macromolecule remained stiff. Longer linkers (up to 8,000 base pairs) appeared to coil up between the beads, allowing for movement in the chain. Surprisingly, when the researchers reapplied the magnetic field to stretch the long links, they once again became rigid.
"Our vision of what's happening is that DNA allows some wiggle room between particles and gives the chain elasticity," Biswal said. "But if the particles are pulled far enough apart, you stress the bridge quite a bit and reduce the freedom it has to move."
Being able to engineer such a wide range of flexibilities allows for more complex materials that can be actuated with magnetic fields, Biswal said.
"This research is interesting because until now, people haven't been able to make flexible chains like this," Byrom said. "We want to be able to explain what's happening across a broad range of polymers, but if you can only make rigid chains, it sort of limits what you can talk about."
Now that they can create polymer chains with predictable behavior, the researchers plan to study how the chains react to shifting magnetic fields over time, as well as how the chains behave in fluid flows.
|Contact: Mike Williams|