CAREER: Shape Responses of Ultrathin Hydrogel Microcapsules Eugemoa Kharlampieva, University of Alabama at Birmingham, DMR Environmental control over material shape is a key parameter in developing the next generation of ‘intelligent’ materials capable of various transformations to perform specific functions. A particle that can controllably alter shape is equally important as those with various static shapes since it offers unique opportunities in targeted drug delivery and transport phenomena. For example, red blood cells (RBC) reversibly deform in the hydrodynamic flow to efficiently navigate within blood vessels. Their various shape transformations protect RBCs from destruction by viral, enzymatic, or osmotic mechanisms. The Kharlampieva group is developing a novel class of shape- adaptable materials using hollow hydrogel microparticles (capsules) of specific shapes to gain fundamental understanding of pH-induced capsule shape transformations. This year we have developed hydrogel capsules with pH-induced transitions from discoids to oblate ellipsoids. The pH-triggered change in capsule volume resulted in anisotropic out-of-plane swelling leading to the discoidal-to-ellipsoidal shape transformations (Fig. 1). The degree of this shape transition was controlled by the pH-tuned volume change, which in turn was regulated by the capsule wall composition. We also observed a 3-fold greater swelling/shrinkage in radial dimensions for one- component capsules than that for the two-component capsules. These differences in aspect ratios were due to a greater degree of the circular face bulging for soft one- component capsules compared to that for more rigid two- component capsules (Fig 2). Fig. 2. Schematics of solid cores and one- and two-component capsules at pH = 7.4 and pH = 4. (a) with dimensions of a bulged discoidal capsule (b). Fig. 1. 3D reconstructions of confocal microscopy images of discoidal (PMAA- PVPON) 5 hydrogel capsules at their swollen (a) and de-swollen (b, c) states.

Fig. 1. Undergraduate student Fox Williams and Graduate student Bing Xue discuss syntheses of shaped hollow hydrogels capsules and porous hydrogel particles. Fig. 2. Graduate student Jun Chen mentored NSF REU student Thaige Gompa during Summer Thaige won a 2nd Prize at the Summer 2014 UAB Expo in the category of Physical Science and Engineering. CAREER: Shape Responses of Ultrathin Hydrogel Microcapsules Eugemoa Kharlampieva, University of Alabama at Birmingham, DMR o This grant has supported 2 graduate students, Bing Xue and Jun Chen. o Overall, 3 graduate and two undergraduate students have been working on the NSF project. One of them, Sasha Zavgorodnya, was recently awarded a Research Fellowship from Department of Chemistry at UAB. She mentored a Hoover High School student Aashlesha Pathak during Summer o Students of the Kharlampieva Group served as judges for local Undergraduate Research Expositions in Spring and Summer o The Kharlampieva Group hosted 1 NSF REU 2014 student Thaige Gompa (Mississippi State University). He was awarded a 2nd Place at the Undergraduate Summer 2014 UAB Research Exposition. Fig. 3. Graduate student Sasha Zavgorodnya (right) mentors Hoover high school student Aashlesha Pathak. The students work together on multilayer hydrogels capable of temperature- triggered shape-responses