Direct Writing and Actuation of Three-Dimensionally Patterned Hydrogel Pads on Micropillar Supports

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Written by: Grant England AP225 Fall, 2011

Info

Title: Direct Writing and Actuation of Three-Dimensionally Patterned Hydrogel Pads on Micropillar Supports

Authors: Lauren D. Zarzar, Philseok Kim, Mathias Kolle, C. Jeffrey Brinker, Joanna Aizenberg, and Bryan Kaehr

@Harvard: http://onlinelibrary.wiley.com/doi/10.1002/ange.201102975/pdf

Keywords

Actuation, gels, hybrid materials, multi-photon lithography, micro patterns, hydrogel

Summary

The main results of this paper were the extension of the hydrogel actuation model to include the ability for unconstrained actuation and local actuation of high aspect ratio structures in response to various stimuli (pH, temperature, etc.).

Methods and Results

By using a multiphoton lithographic technique to initiate the polymerization of the hydrogel, the hydrogel can be patterned three-dimensionally onto a substrate, which allows for greater swelling of the hydrogel and therefore a greater amount of actuation of the micropillars. Additionally, the patterning method allows for localized areas of pillars to be actuated by the hydrogels response characteristic as seen in the figures below.

Hgel1.jpg Hgel2.jpg

The figures also show the set-up used for the multi-photon lithography for patterning of the hydrogel. Additionally, in the paper they discuss methods by which multiple different types of hydrogel can be patterned onto the same substrate in an interlocking pattern in order to actuate structures in response to more than one stimulus. Finally, by modifying a hydrogel with a fluorophore (rhodamine) it was possible to create a patterned fluorescence which was only visible when the concentration of the fluorophore was high enough (i.e. when the hydrogel was in the contracted state), so a programmable fluorescent response to a stimulus was obtained.

Conclusions

The paper described a way to create arbitrary three-dimensional patterns of hydrogel via multi-photon lithography which can lead to a large amount of applications--especially when combined with the ability to create hybrid systems which can respond to multiple orthogonal stimuli simultaneously. The results of this paper could be extended to more complex "skeletal" structures in order to create a more complicated, bio-mimetic device.