(6fm) Self-Assembly, Elasticity, and Rheology of Soft Materials

Amorphous materials – including emulsions, foams, gels, pastes, glasses, etc. – have been, and may well remain, some of the most technologically and industrially relevant soft materials. The somewhat fuzzy boundary between fluid- and solid-like behaviors of these materials is largely what makes them so practically useful, but their intrinsic structural complexity has severely limited our ability to understand and prescribe how macroscopic behavior arises from microscopic properties. During my Ph.D. studies in Prof. David Weitz's lab at Harvard University I focused primarily on understanding the elasticity and solidification of amorphous materials. There I discovered that the liquid and solid regimes of quiescent, compressed emulsions are separated by a thermally induced "unjamming" instability of the solid: the solid falls apart when the thermal agitation of the droplets that compose it are strong enough to locally and continually yield it. The properties of emulsions that make this instability possible are also shared by foams and many pastes, and understanding how material failure via unjaming may affect the properties of these and other materials will require developing new, non-invasive experimental and analytical tools to study them. Thus far I have worked on integrating light scattering, MRI, microscopy, rheology, and computational tools to better understand this transition in emulsions, microgel suspensions, and colloidal glasses. More broadly, understanding and controlling the elasticity and flow behavior of soft materials is a long-standing fundamental problem with a myriad practical applications, and I am excited to continue my work in this area.

Introducing various kinds of microscopic order into soft materials is another, very powerful way to control the mechanical, rheological, electrical, and optical properties of these materials; however, despite an incredible diversity of bottom-up and top-down approaches that accomplish this in a laboratory environment, there is still a need for scalable methods that can organize colloids composed of inexpensive ingredients. Most recently, as a postdoctoral associate in Prof. Paul Chaikin's lab at New York University, I have focused on the self-assembly and frustrated crystallization of particles adsorbed on curved surfaces. However, I have also begun work on a new technology that will enable scalable colloidal self-assembly by in situ capacitive deionization of colloidal suspensions, and which I expect will become a major focus of my upcoming research. The process depends only on surface charging – a nearly universal property of colloidal particles – to induce ordering, using supercapacitive electrodes immersed in the fluid to modulate the ionic strength of the suspension: a process that can be combined with ordered templates for epitaxial assembly. Thorough deionization can dramatically affect the optical properties of colloidal suspensions, and precisely modulating the salinity of a suspension of oppositely charged particles can induce ordering and crystallization. While I am still working to catch up with state-of-the-art electrode fabrication techniques, these processes are mature and reliable enough to make it possible to print large-scale, locally-addressable electrodes. Combining them with large-scale, perfectly ordered templates, will make it possible to fabricate large-scale structured colloids.

Teaching Interests:

A person's ability to work well as part of a team is often a crucial part of a successful career. As a TA for graduate and undergraduate classes, as well as a student myself, I have found that encouraging students to work in groups helps the class cover more advanced material and helps students sharpen the basic social skills required to work well with others. I look forward to working with students to incorporate more collaborative and peer learning approaches to the classroom, and to help them become successful scientists and engineers.

I am also interested in helping more people understand how amazing science and engineering can be. I have found that explaining what makes the soft materials that surround us – foods, toiletries, plastics, digital displays, etc. – interesting and special is a concrete and appealing way to introduce people to physical and chemical concepts that they might otherwise have found to be alien or abstract. I would welcome the opportunity to develop a cross-disciplinary class aimed at reaching out to people who might not have though science or engineering was for them, and would be especially willing to work with high-school science teachers to help them broaden and enrich their lesson plans: I believe helping students see science and engineering as an integral part of their lives early on will spark their curiosity and make them more likely to become scientists and engineers themselves.