(5ba) Soft Materials for High Performance Structural Materials, Bio-Implants, and Energy Storage Materials

My research interest is investigating the processing/fabrication-structure-property relationships across multiple length scales for various technologically relevant soft materials. Common examples of soft materials include gels/hydrogels, polymer melts, biological tissues, etc [1, 2]. The motivation of my research will be applying these soft materials in various challenging applications ranging from energy storage to new generation smart materials.

Presently, I am a postdoctoral researcher working in the polymer characterization and measurement group at the National Institute of Standards and Technology (NIST), where I am developing microfluidics/lab-on-chip techniques to obtain polymeric materials from sustainable sources. Before joining NIST, I was a post-doctoral research associate at the Polymer Science and Engineering Department of University of Massachusetts-Amherst. I was involved in investigating surface, near surface and mechanical characterization of gel/hydrogel/elastomeric materials. The mechanical properties of gels present qualitatively contradictory behavior; they are commonly soft but also notoriously brittle. We investigated the elasticity and fracture behavior of swollen polymer networks using a simple experimental method to induce cavitation within polyacrylamide hydrogel, a common material used in many biological applications. A transition from reversible cavitation to irreversible fracture was observed with the increase of polymer volume fraction [3]. Adapting scaling theories, it is shown quantitatively that the transition from reversible cavitation to irreversible fracture depends on the polymer volume fraction and an initial defect length scale. The use of cavitation experiments permits characterization of network properties across length scales ranging from µm to mm. We anticipate that these results significantly enhance the understanding of mechanical properties of soft materials, both synthetic and biological.

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 investigated the adhesion and mechanical properties of commercially available contact lenses (hydrogels) by developing a custom built setup. The set-up is also equipped with a liquid cell, which enabled us to measure adhesion forces for various gels/hydrogels/elastomers in different environmental conditions. Adhesion properties of polymeric materials can be altered by incorporating topological patterns on the surfaces. However, conventional patterning methods, including photo- and imprint lithography, are difficult to apply to non- planar surfaces. During my postdoctoral research at Amherst, I developed a technology based on surface wrinkling technique to incorporate novel structures on the non-planar contact lens surfaces [4, 5]. Incorporation of such structure resulted in significant performance improvement (clinical trial will be performed).

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 [6-10]. 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:

? Mechanics of soft materials

? Hierarchical carbon materials for energy storage applications

? Large scale development of carbon thin films for electronics materials

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, as a mentor during my postdoctoral work, and as a supervisor during my industrial tenure. I can teach undergraduate and graduate level courses on transport phenomenon, engineering mechanics, engineering mathematics, chemical reaction engineering, polymer processing, and soft materials mechanics. I also intend to develop a new interdisciplinary course on fabrication and characterization of nanostructured materials for engineering applications, viscoelasticity of polymers and biopolymers: theory and simulation, Soft Materials Mechanics.

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, Crosby AJ. Cavitation rheology and fracture behavior of polyacrylamide gels, submitted; Kundu S, Crosby AJ. Cavitation rheology and fracture mechanics of polyacrylamide hydrogels. American Physical Society -March meeting, Pittsburgh, USA, 2009.

4. Kundu S, Crosby AJ, Sharma R. Adhesion Behavior of Non-planar Wrinkled Surfaces, in preparation; Kundu S, Crosby AJ, Sharma R. Adhesion Behavior of Non-planar Wrinkled Surfaces. American Physical Society -March meeting, Pittsburgh, USA, 2009.

5. Breid D, Kundu S, Denic V, Crosby AJ. Curvature effect on the wrinkle morphology, in preparation.

6. Kundu S, Grecov D, Rey AD, Ogale AA. Shear flow induced microstructure of a synthetic mesophase pitch, Journal of Rheology 53(1):85-113(2009).

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

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

9. Kundu S, Naskar AK, Ogale AA, Anderson D, Arnold JR. Observations on a low-angle x-ray diffraction peak for AR-HP mesophase pitch, Carbon 46(8):1166-1169 (2008).

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