This laboratory is supported by:

The National Science Foundation, Directorate for Engineering Chemical, Bioengineering, Environmental, & Transport Systems Division (CBET) under the Particulate and Multiphase Processes Program (CBET-2002797):

Collaborative Research: Experimental and Computational Studies of Flow and Clogging of Deformable Particles under Confinements.
Squishy, deformable particles play an important role in many fields of science and engineering, from the biological cells to droplets of fatty oils in water that make up emulsions like mayonnaise, peanut butter, and milk. Microfluidic devices with tiny channels of varying widths are used to process mixtures of deformable particles and fluids and to manipulate DNA molecules. However, microfluidic devices frequently clog near constrictions, which is expensive since the device must be replaced when this occurs. Clogging has been studied extensively for rigid particles, like grains flowing out of a silo, but clogging of deformable particles is less well understood. In particular, it is unclear how particle deformability and stickiness or cohesion affects clogging. For example, will deformable and cohesive particles change shape and flow past each other at constrictions, or will they form arches and clog the system? This project combines experiments of emulsion droplets flowed through microfluidic devices with novel computer simulations of deformable particles to understand how they clog. This work will aid in future designs of critical microfluidic devices involved in industrial processing, filtration, and analysis of biological samples of cell-fluid mixtures.

The National Science Foundation, Directorate for Engineering Division of Civil, Mechanical, and Manufacturing Innovation (CMMI) under the Mechanics of Materials and Stuctures (CMMI-1463455):

Collaborative Research: Mechanics of Granular Acoustic Meta-materials with Engineered Particles and Packings.
Acoustic meta-materials are engineered materials enabling the control of sound waves. Granular acoustic meta-materials are constructs of particles in periodic and disordered arrangements. This project seeks a fundamental understanding of the acoustic and mechanical response of granular packings where the particles possess specific engineered properties. These materials exhibit a key acoustical property, that is acoustic band gaps. Band gaps prevent sound of certain frequencies to propagate. Meta-materials exhibiting acoustic band gaps have applications for vibration isolation, sound wave communication, acoustic super-lenses, acoustic diodes, and acoustic cloaking devices. This project will combine engineered particle shapes and materials with specially designed spatial arrangements of the particles to allow detailed control over the acoustic properties of the material. This project will involve several undergraduates in research each year through partnerships between the collaborating institutions, one of which is minority-serving. Outreach initiatives include an annual lecture series on granular media. Teaching modules for use by the International Centre for Theoretical Physics will be developed for teaching basic computational research skills to graduate students from developing countries.

The National Science Foundation, Directorate for Engineering Chemical, Bioengineering, Environmental, & Transport Systems Division (CBET) under the Particulate and Multiphase Processes Program (CBET-0968013):

Collaborative Research: Experiment, simulation, and theory of slowly driven granular materials --- from micro-state statistics to macroscopic properties.
We are carring out a set of coordinated experiments, numerical simulations, and theoretical studies to provide predictive and quantitative descriptions of the structural and mechanical properties of static and slowly driven granular materials. Dense granular media are ubiquitous in nature and occur in many industrial applications. However, there is currently no fundamental understanding of how to uniquely characterize the state of a dense granular system using macroscopic descriptors. In our proposed research, we seek such a description using a systematic, bottom-up approach in which we first characterize microstate probabilities of mechanically stable granular packings and then utilize them to predict macroscopic behavior. In our studies of static particle packings, we will measure the probabilities of distinct microscopic states (cataloged by the particle positions) for different packing preparation protocols and particle properties such as shape, friction, and size polydispersity. We will also determine the number of microscopic states corresponding to macroscopic observables, such as the volume fraction, elastic constants and mechanical strength. By combining our results for microstate probabilities and the density of macro-states, we will determine the microstates that contribute significantly to ensembleaveraged quantities. We will also study the evolution of slowly driven systems, in which transitions from one microstate to another occur. In particular, we will measure the transition probabilities in experiments and numerical simulations of tapping excitations and quasi static shear. We will then develop master equation approaches to predict the steady state microstate distributions and corresponding macroscopic variables as a function of the intensity of the driving mechanism.

The National Science Foundation, Math, Physical Sciences Department of Materials Research under the Partnerships for Research and Education in Materials (PREM) Program (DMR-0934206):

PREM: City College-Chicago MRSEC Partnership on the Dynamics of Heterogeneous and Particulate Materials .
The Partnership in Research and Education in Materials (PREM) at the City College of New York (CCNY) involves a collaboration with the Materials Research Science and Engineering Center (MRSEC) at the University of Chicago. The PREM has two broad goals: to provide the highest quality research and education opportunities in material dynamics; and to use CCNY's diverse and high-quality student body and research university status to drive permanent added participation of under-represented groups in materials science. The overarching goal of the research is to develop methodology for description of material dynamics. This work has potential for major impact in many fields.

The National Science Foundation, Math, Physical Sciences Department of Materials Research under the Faculty Early Career Development (CAREER) Program (DMR-0134837):

CAREER: Granular Media: Experimental Kinetic Theory.
Experimental determination of the region of applicability of dense gas kinetic theory and other standard statistical methods applied to granular materials for both idealized and industrially relevant forcing and to incorporate research experience into the undergraduate and graduate science curriculum.

The City University of New York, Office of Academic Affairs Equipment Grant:

High speed/high resolution microparticle visualization system and diffusing-wave spectrometer.
Non-equilibrium systems near jamming and glass transitions. Acquisition of Microscope and Laser for experimental studies of particulate systems.

The Professional Staff Congress of The City University of New York, under the Research Award Program: PSC-CUNY 65500-00-34.

Three-dimensional Force Chains in Granular Media..
Continued development of novel tomographic technique for determining the three dimensional density and stress distribution in compress granular media using the photoelastic effect of the particles.

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