HAIRS

HAIRS: Hydrogel-Actuated Integrated Responsive Systems
Joanna Aizenberg, Harvard University

Responsive behavior, which is intrinsic to natural systems, is becoming a key requirement for advanced artificial materials and devices, presenting a substantial scientific and engineering challenge. We designed dynamic actuation systems by integrating high{aspect-ratio nanocolumns or nanofins, either free-standing or substrate-attached, with a hydrogel layer. The embedded structures are put in motion by the “muscle” of the hydrogel, which swells or contracts depending on the humidity level, pH or temperature. This actuation results in a fast reversible reorientation of the nanocolumns and nanofins from tilted to perpendicular to the surface. By further controlling the stress yield in the hydrogel by patterning, the formation of a variety of elaborate reversibly actuated micropatterns is demonstrated. Dynamic control over the movement and orientation of surface nanofeatures at the micron and submicron scales may have exciting applications in actuators, microfluidics, or responsive materials.

Nano-Bristles

“From the structure of DNA to nautical rope to distant spiral galaxies, helical forms are as abundant as they are useful in nature and manufacturing alike. Researchers at the Harvard School of Engineering and Applied Sciences (SEAS) have discovered a way to synthesize and control the formation of nanobristles, akin to tiny hairs, into helical clusters and have further demonstrated the fabrication of such highly ordered clusters, built from similar coiled building blocks, over multiple scales and areas.

The finding has potential use in energy and information storage, photonics, adhesion, capture and release systems, and as an enhancement for the mixing and transport of particles. Lead authors Joanna Aizenberg, Gordon McKay Professor of Materials Science at SEAS and the Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute for Advanced Study, and L Mahadevan, Lola England de Valpine Professor of Applied Mathematics at SEAS, reported the research in the January 9 issue of Science.”

Credit: Courtesy of Aizenberg lab at the Harvard School of Engineering and Applied Sciences
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