(5bk) Soft Materials Mechanics towards Development of High Performance Structural Materials, Bio-Implants, and Energy Storage Materials

My research interest is achieving a fundamental understanding of various aspects of soft materials such as flow, interfacial, mechanical properties and their interrelationship with microstructure. Soft materials are found in many places, ranging from all life forms such as blood, cells, tissues, mucus to commonly used paints, cosmetic products, hydrogels and food materials. Properties of these materials depend on their microstructure, which can be altered using flow field or stress. Also, materials with novel microstructures (in various length scales) are fabricated using top-down and bottom-up approaches ^{1, 2} and a structure-property-processing relationship of these materials needs to be developed for efficient materials design.

Presently, in my postdoctoral work I am investigating surface, near surface and mechanical characterization of hydrogel materials. The mechanical characterization of hydrogels is extremely difficult due to their inherent compliance and fragility. To overcome these problems a new technique, cavitation rheology, is being developed for the measurement of mechanical properties on small length scales, e.g. 1-100 µm, at any arbitrary location within a soft material. The technique involves growing a cavity at the tip of a syringe needle and monitoring the pressure of the cavity at the onset of instability. This critical pressure is directly related to the local modulus of the material. The technique is presently being investigated for polyacrylamide, a chemically crosslinked gel^{3, 4}. Successful development of this technique will lead to measurement of modulus of biological tissues in vivo. Furthermore, the simplicity of this technique not only allows easy implementation into variety of materials systems, but also for high throughput testing.

For some applications it is important to know the adhesion and frictional behavior of hydrogels and one such example is contact lenses. In an industry sponsored project, I have developed an experimental set-up to measure the adhesion behavior of contact lenses and other hydrogels using a contact mechanics approach. Our set-up is also equipped with a liquid cell and in an ongoing study we are measuring low adhesion forces typically experienced in a liquid environment. We are also investigating the effect of pattern surfaces (on both hydrogels and elastomers) on the adhesion behavior at various environmental conditions ^{5, 6}. The patterned surfaces are created using novel fabrication techniques such as, wrinkling, micro-molding, lithography, etc.

In my Ph.D. research I have studied the flow and three dimensional microstructure of a liquid crystalline carbonaceous material (mesophase pitch) for different flow conditions, such as steady shear flow, dynamic flow, and processing flow using polarizing optical microscopy and X-ray diffraction^7-11. The evolution of microstructure in different flow conditions was uniquely studied in three orthogonal planes. The systematic understanding of flow and its effect on microstructure helped us to predict/model the complex flow behavior and microstructural evolution of this material, which in turn will help to design carbon materials, such as carbon fibers, carbon-carbon composites, and fuel cell separators in more efficient ways. My dissertation, ?Investigation of flow and microstructure in rheometric and processing flow conditions for liquid crystalline pitch', has been awarded the Best Dissertation in Carbon Science, 2007 for ?outstanding scientific achievement' by the Elsevier-Carbon Journal.

The research program that I plan to develop will largely build on my postdoctoral and doctoral research and specifically, I would like to develop a research program in the following areas:

? Flow and microstructure of anisotropic particle systems,

? Adhesion behavior of hydrogels at various environmental conditions,

? Large scale development of graphitic thin films from carbonaceous precursors and their transfer on elastic materials for flexible electronics applications,

? Development of porous and graphitic carbon materials with hierarchical structure for energy storage applications, such as, supercapacitors and hydrogen storage.

In addition to research, I am passionate about teaching and am inspired to educate and to mentor future scientists and engineers to meet the challenges of today's ever-changing technologies. My teaching philosophy has been developed through my experience as a lab and teaching assistant during my graduate school days, and as a supervisor during my industrial tenure. I can teach traditional undergraduate and graduate level chemical engineering courses. In addition, I intend to offer advanced graduate level courses in polymer adhesion, fabrication and characterization of nanostructured materials, viscoelasticity of polymers and biopolymers: theory and simulation.

References:

1. Ladet S, Laurent David L and Alain Domard A. Multi-membrane hydrogels. Nature 452, 76-79 (2008).

2. Dzenis Y. Structural Nanocomposites. Science 319, 419-420 (2008).

3. Kundu S, Zimberlin JA, Crosby AJ. Cavitation rheology and fracture mechanics of polyacrylamide hydrogels. American Physical Society -March meeting, New Orleans, USA, 2008.

4. Kundu S, Zimberlin JA, Crosby AJ. Cavitation rheology and fracture behavior of polyacrylamide gels, in preparation.

5. Kundu S, Crosby AJ, Sharma R. Adhesion behavior of a model hydrogel in various environmental conditions, in preparation

6. Kundu S, Crosby AJ. Adhesion of patterned surfaces under water, in preparation.

7. Kundu S, Grecov D, Rey AD, Ogale AA. Shear flow induced microstructure of a synthetic mesophase pitch, submitted.

8. Kundu S, Ogale AA. Rheostructural studies on a synthetic mesophase pitch during transient shear flow, Carbon 44(11): 2224-2235 (2006).

9. Kundu S, Ogale AA. Microstructural effects on the dynamic rheology of a discotic mesophase pitch, Rheologica Acta 46(9):1211-1222 (2007).

10. Kundu S, Naskar AK, Ogale AA, Anderson D, Arnold JR. Observations on a low-angle x-ray diffraction peak for AR-HP mesophase pitch, In press, Carbon, doi:10.1016/j.carbon.2008.03.014.

11. Kundu S, Ogale AA. Microstructure development of a synthetic mesophase pitch during processing flow, in preparation.