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The Shankar Research Group

Research

Multifunctional Nanograined Materials

Refined nano-scale grain structures can demonstrate novel functional properties that accompany their enhanced mechanical properties. We are examining scalable approaches for creating such microstructures at surfaces and in bulk-forms in Al, Mg and Ti alloys and their technological implications for structural and biomedical applications.  Ongoing research in our group has also focused on identifying the underlying physical phenomena that leads to the creation of nanograined materials with specific microstructural attributes from severe shear deformation. This effort has coalesced around the delineation of Rate-Strain-Microstructure (RSM) maps that project the quantitative aspects of nanostructures on a space that is parameterized as functions of the thermomechanics of deformation that spawned their refinement.

Supported by NSF grants: 0826010, 0927410, 1233909 and 1404641

Mechanics of Deformations at the Micro-Scale

Understanding the implications of the stochasticity, size-effects and constitutive properties of deformation of metals at the micrometer and sub-micrometer length-scales is critical for controlling process and product outcomes in mechanical microforming and micromachining methodologies. We are working on new experimental paradigms for exploring the mechanics of deformation in microdeformation configurations. For this, we have a developed a micromanufacturing platform that can perform multiaxial manipulation within the sample-chamber of a scanning electron microscope. By utilizing secondary electron, backscattered electron and electron backscattered diffraction analysis, we are examining in situ the mechanics and microstructural consequences of mechanical forming and material removal at small length-scales. 

Supported by NSF grants: 0856626 and 1030265

Hierarchical Nanostructured Surfaces

Surfaces with hierarchies composed of nano-scale structures on micro-scale features endow novel functionalities in several instructive illustrations from the natural world. A common example is the self-cleaning, superhydrophobicity of the lotus-leaf that is characterized by a fine micro-scale texture that is superimposed with dense fibrillar nanostructures. In the animal world, hierarchical structures lead to low drag in textured, self-cleaning skin of the shark, the antireflective eye of the housefly and manifest the phenomenon of structural color in birds, fishes and quite brilliantly in iridescent butterfly wings. We are working on new direct-write approaches for the scalable manufacture of such complex hierarchies in polymeric materials to offer novel biomimetic engineering opportunities, while potentially advancing emerging paradigms in soft-lithography.

Direct Transduction of Photonic Energy into Mechanical Work

Azobenzene-functionalized polymers can transduce light directly into mechanical work either via trans-cis isomerization or via the trans-cis-trans reorientation of the azo groups. We are examining approaches centered on design of novel compositions and mechanical designs for enhancing the efficiency of this transduction and maximizing the achievable power densities. Novel microsystem and biomedical system opportunities are anticipated by integrating these ideas in photomechanically-actuated mechanisms. 

Supported by NSF grants: 1435489 and Air Force Office of Scientiic Research

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