(4ao) Mechanics of Bio-Inspired Soft Responsive Coatings

The mechanical properties of materials with spatial gradients in composition and structure, or graded materials, are of great importance in different fields such as biology, medical devices, biomechanics, sport physics, tribology, rheology, and fracture mechanics. Examples of man-made graded solids go back to the blade structure in Japanese swords. Recent advances in biomedical devices, biological interfaces, drug delivery, cosmetics, soft robotics and soft adhesion have all underlined the crucial importance of graded soft materials in different novel applications. Despite these emerging technologies, little is known about the important role of dynamic viscoelastic properties on the overall functionality of graded soft materials. My long-term research goal is to understand the mechanics of bio-inspired soft materials for sustainable applications in human life and health. Recognizing that viscoelastic coatings are a common feature in soft graded materials, in the short term my lab will focus on utilizing a series of recently developed experimental methods and chemical mechanisms to (1) find easy and reliable methods for developing soft viscoelastic coatings from polymer solutions based on simple principles of fluid dynamics in atomization and coating, (2) understand the role of soft viscoelastic coatings on overall dynamic properties of composite structures by a combination of well-thought experiments and inspiration from natural systems, and (3) study the nonlinear mechanics of soft coatings in fatigue and extreme mechanical conditions using novel experimental techniques. Each of these research goals is closely related to soft coatings in natural structures, which provides opportunities for biomimicry and extensive multidisciplinary research.

Research Experience:

I am currently a postdoctoral lecturer in the department of Mechanical Engineering at MIT. I have also been working with Professors Niels Holten-Andersen and Gareth McKinley as a postdoctoral researcher in the Laboratory of Bio-inspired Interfaces and the Non-Newtonian Fluids laboratory (DMSE & MechE departments at MIT), where I have used my knowledge of fluid dynamics and soft matter mechanics to develop and characterize bio-inspired functional coatings. I have used insights from the biochemistry of metal-coordination in marine creatures, such as mussel byssus, to develop simple functional coatings from hydrogels. These novel bio-inspired responsive coatings have many promising applications in human life and health. In collaborative research with L’Oréal, I have applied these coatings to human hair and shown that, through the shape-memory mechanism of the coating, we can style both fibers and bundles of coated human hair. Presently, our collaborators in L’Oréal are transforming our hydrogel coatings into a commercial product for hairstyle/cosmetic applications and together we have recently filed a relevant patent application. My knowledge and expertise of fluid dynamics for coating processes and mechanics of soft materials will propel my future research in the area of soft responsive coatings.

Postdoctoral Project

Developing Responsive Hydrogel Coatings for Human Hair

(MIT & L'Oréal, USA, advised by Prof. Gareth McKinley & Prof. Niels Holten-Andersen)

Origins of Glassy/Rubbery Behavior in Weak Colloidal Gels

(MIT & CEA France, collaboration with Prof. Gareth McKinley & Dr. Arnaud Poulesquen)

PhD Thesis

Nonlinear Dynamics of Complex Fluids in Fragmentation, and Fracture

(MIT, Mechanical Engineering Department, Advised by Prof. Gareth McKinley)

My teaching experience in MIT (Mechanical Engineering Department) :

Leading instructor for Advanced Fluid Mechanics (2.25), graduate level, Fall 2021.

Instructor for Advanced Fluid Mechanics (2.25x), MIT edX, graduate level, Fall 2020 and Spring 2021.

Instructor for Numerical Computation for Mechanical Engineers (2.086), undergraduate level, Spring 2021.

Instructor for Advanced Fluid Mechanics (2.25), graduate level, Fall 2020

Instructor for Thermal-Fluids Engineering (2.006), undergraduate level, Fall 2020

Instructor for Advanced Fluid Mechanics (2.25), graduate level, Fall 2019

Instructor for Advanced Fluid Mechanics (2.25), graduate level, Fall 2017

Teaching philosophy and interests:

My teaching experience goes back to high-school days when I acted as our Math Olympiad trainer after receiving a national medal in the competition myself. I have been a teaching assistant for different courses during my undergraduate, masters and PhD. During my post-doctoral years, I have been a lecturer in the MechE department at MIT for more than four semesters and delivered teaching for both graduate and undergraduate courses. It makes me very proud to receive positive feedback from students every year and compliments such as “Bavand is hands down the best teacher that I have ever had. His grasp of the material is unparalleled and his ability to explain to any and every level of understanding is amazing. He has a way of making the subject less intimidating and more fun.” or “In these unusual times, Bavand deftly maneuvered his way through the digital teaching world and provided us with a thorough learning experience that was funny, enthusiastic, and greatly informative. His solutions and open discussions helped a lot, and his demonstrations were very fun...he is a pedagogical hero in this COVID era.” are both humbling and inspiring. One of my great contributions has been teaching 2.25 (Advanced Fluid Mechanics for graduate level) and 2.25x (through the MIT-edX platform) with Professor Gareth McKinley. The historical legacy of this course and its contributions to engineering education are well documented. Through courses such as 2.25, Ascher Shapiro (MIT) exported some great scientific ideas such as control volume analysis (originally from Prandtl) to the engineering world. The omnipresent use of this concept in our engineering education underlines the importance of connecting bridges between fundamental sciences and engineering applications. Thus, I believe that teaching should be a transfer of principles of thinking that enables students to both use and create these connecting bridges in their future challenges. This forms the core of my teaching philosophy, which I rigorously follow. I will be excited to teach both undergraduate and graduate level courses in transport phenomena, fluid dynamics of Newtonian and non-Newtonian liquids, thermal sciences, experimental measurements, and soft-matter mechanics that are within the core curriculum of chemical engineering departments.

Selected Patents and Publications (chronological order):

1. Amin, S., Holten-Anderson, N., Keshavarz, B., McKinley, G.H., Muthukrishnan, S. and Zarket, B., LOreal SA and Massachusetts Institute of Technology, 2020. Responsive coatings for hair fibers. U.S. Patent Application 16/600,233.
2. Keshavarz, B., Rodrigues, D.G., Champenois, J.B., Frith, M.G., Ilavsky, J., Geri, M., Divoux, T., McKinley, G.H. and Poulesquen, A., 2021. Time–connectivity superposition and the gel/glass duality of weak colloidal gels. Proceedings of the National Academy of Sciences, 118(15).
3. Keshavarz, B., Zarket, B., Amin, S., Rughani, R., Muthukrishnan, S., Holten-Andersen, N. and McKinley, G.H., 2021. Characterizing viscoelastic properties of synthetic and natural fibers and their coatings with a torsional pendulum. Soft Matter, 17(17), pp.4578-4593.
4. Keshavarz, B., Houze, E.C., Moore, J.R., Koerner, M.R. and McKinley, G.H., 2020. Rotary atomization of Newtonian and viscoelastic liquids. Physical Review Fluids, 5(3), p.033601.
5. Geri, M., Keshavarz, B. (co-first author), Divoux, T., Clasen, C., Curtis, D.J. and McKinley, G.H., 2018. Time-resolved mechanical spectroscopy of soft materials via optimally windowed chirps. Physical Review X, 8(4), p.041042.
6. Lai, E., Keshavarz, B. and Holten-Andersen, N., 2019. Deciphering how the viscoelastic properties of mussel-inspired metal-coordinate transiently cross-linked gels dictate their tack behavior. Langmuir, 35(48), pp.15979-15984.
7. Bouzid, M., Keshavarz, B. (co-first author), Geri, M., Divoux, T., Del Gado, E. and McKinley, G.H., 2018. Computing the linear viscoelastic properties of soft gels using an optimally windowed chirp protocol. Journal of Rheology, 62(4), pp.1037-1050.
8. Sadman, K., Wang, Q., Chen, Y., Keshavarz, B., Jiang, Z. and Shull, K.R., 2017. Influence of hydrophobicity on polyelectrolyte complexation. Macromolecules, 50(23), pp.9417-9426.
9. Regitsky, A.U., Keshavarz, B., McKinley, G.H. and Holten-Andersen, N., 2017. Rheology as a mechanoscopic method to monitor mineralization in hydrogels. Biomacromolecules, 18(12), pp.4067-4074.
10. Geri, M., Keshavarz, B., McKinley, G.H. and Bush, J.W., 2017. Thermal delay of drop coalescence. Journal of Fluid Mechanics, 833.
11. Keshavarz, B., Divoux, T., Manneville, S. and McKinley, G.H., 2017. Nonlinear viscoelasticity and generalized failure criterion for polymer gels. ACS Macro Letters, 6(7), pp.663-667.
12. Keshavarz, B., Houze, E.C., Moore, J.R., Koerner, M.R. and McKinley, G.H., 2016. Ligament mediated fragmentation of viscoelastic liquids. Physical Review Letters, 117(15), p.154502.
13. Eral, H.B., Safai, E.R., Keshavarz, B. (co-first author), Kim, J.J., Lee, J. and Doyle, P.S., 2016. Governing principles of alginate microparticle synthesis with centrifugal forces. Langmuir, 32(28), pp.7198-7209.
14. Keshavarz, B., Sharma, V., Houze, E.C., Koerner, M.R., Moore, J.R., Cotts, P.M., Threlfall-Holmes, P. and McKinley, G.H., 2015. Studying the effects of elongational properties on atomization of weakly viscoelastic solutions using Rayleigh Ohnesorge Jetting Extensional Rheometry (ROJER). Journal of Non-Newtonian Fluid Mechanics, 222, pp.171-189.