By increasing or decreasing the volume of microstructures dynamically, Shear hopes to be able to better understand a phenomenon known as quorum sensing, where bacteria coordinate their gene expression according to the density of their population. Quorum sensing is important in the pathology of some disease-causing bacteria, such as Pseudomonas aeruginosa.
The hydrogels created by Shear and Kaehr are made of protein molecules that have been chemically bound together using a focused laser beam, a process known as photofabrication.
The laser causes amino acid side chains to link en masse and this builds a solid protein matrix. The protein scaffold is built layer by layer, much like a raster scanner.
"It's a little bit like a three-dimensional Etch-a-Sketch," says Shear.
Other high resolution structures the researchers developed include tethers that connect microspheres to surfaces, flower- and fern-like structures, and micro-hands that are less than a quarter the diameter of a hair, pinky to thumb.
Experimenting with various chemical changes, Shear and Kaehr show that changing pH caused hydrogel bands to bow out at specific points along their length and caused other shapes, like the micro-hands and bacterial chamber, to expand.
Altering ion concentrations caused the fern-like structures to coil and unfurl like fiddleheads emerging from the ground in spring. Adding ions caused contraction of the tether holding the microsphere.
Structures such as these could be used to create better micro- and nano-valves, motors and optics.
Shear says a great advantage of the hydrogels is that they are well suited for controlling and growing cells dynamically and in the environments in which they live.
Waste from the cells can move out of the structures and nutrients and other chemicals, including those added by the res
|Contact: Jason Shear|
University of Texas at Austin