Soft materials:
This research focuses on the properties of common soft materials. We study colloids, emulsions, drops, polymers and gels. Our focus is on understanding the structure of these materials and how this controls their dynamics and properties. We make extensive use of the experimental tools of a soft matter physics lab, including optical microscopy, light scattering and rheology. We also invent new tools and experimental techniques to explore all properties of the material. Much of our focus is on the mechanical properties of the materials and their relationship to the internal dynamics of the structures within the material. Our work is often motivated by technological applications of the materials, and we work with industrial partners to help them solve important problems. In addition, we search for new ways to create materials with interesting properties and high value. We also use soft materials, such as colloidal particles or microgels, as model systems to investigate the behavior of more complex matter.
Mechanical instabilities of armored droplets and colloidal capsules Fluid droplets are often 'armored' with colloidal particles on their surfaces; as a result, they can be very stable against coalescence. I have been studying the mechanical instabilities of these armored droplets, with a view towards seeing how well they can be understood within the framework of the mechanics of thin continuum shells. In parallel, I have been studying the mechanical instabilities of colloidal capsules with thin polymeric shells. Sujit Datta
Elasticity of Emulsions: We use emulsions as a model system to study the onset of elasticity of amorphous packings. By carefully choosing and tuning the properties of the fluids we are able to use conventional mechanical rheology, light scattering, microscopy, and tomography to look at elasticity over a wide range of loads. Rodrigo Guerra 
Exploring deformation in amorphous materials using colloidal glasses as experimental model materials: Colloidal glass provides a unique experimental system with which to study the structure, defects, and dynamics of a generic amorphous material. We probe the elastic, anelastic, and plastic response of the system, with particular focus on identifying specific mechanisms of deformation. Kate Jensen 
Synthesis and characterization of colloids: I’ve been working on the synthesis and characterization of colloids whose refractive index and density can be simultaneously matched in mixtures of polar and non-volatile solvents. Tom Kodger 
Colloidal Gel Failure: When colloidal have a sufficient strong attractive potential they can become trapped in a kinetically arrest state called a gel which behaves as an elastic solid. The mechanical failure of this network is relevant to many industries, ranging from the food industry (yogurt) to paint and cosmetics. I’m studying exactly how the network’s structural integrity degrades at the individual colloid level under a controlled shear in 3D using a confocal microscope. Tom Kodger 
Multiple anticancer drugs oral delivery from o/w nanoemulsion: The nanoemulsion is a lipid based delivery system demonstrating absorption enhancement, so this system is considered an ideal alternative for oral delivery of hydrophobic anticancer drugs. The major advantages of this system include thermodynamic stability, high solubilization potential, dissolution rate improvement and surfactant-induced permeability enhancement. Mingtan Hai 
Charge effects in nonpolar solvent: We investigate the behavior of charged particles in nonpolar solvents in response to an applied electric field. We design and fabricate a cell which allows us to apply an electric field across a particle suspension and directly visualize the particle dynamics. Thus, we study the underlying mechanisms for pattern formation, assembly of structures, electrohydryodynamic instabilities, and nonlinear transport behavior. Understanding of such behaviors is vital for the advancement of technologies, such as electrophoretic displays, in which the ability to manipulate charged particle suspensions with an electric field is essential. Tina Lin 
Soot Dispersion and Electrosteric Stabilization in Nonpolar Solvents: Soot accumulation in automotive engine oils is an important problem, both scientifically and economically. Soot, consisting primarily of agglomerates of particulate carbon, forms heterogeneous, space-filling, weakly attractive gels in oil. Common dispersants used to stabilize soot typically have utilize both electrostatic and steric repulsion mechanisms. In my research, we seek to better understand and differentiate between these stabilization mechanisms in nonpolar solvents by examining concentrated dispersions of fractal carbon black particles in synthetic isoparrafin oils. Joe McDermott 
Gelation and phase separation: We study the aggregation, gelation and phase separation of micron-scale colloidal particles made attractive with the addition of non-adsorbing polymer depletant. We observe morphology changes as a result of the range and strength of the depletion attraction, and that the kinetic arrest in gelation is driven by the process of phase separation. Peter Lu
Drying of complex suspensions: Mixtures of immiscible fluids with colloids can be very complex but they are technologically important for industries such as paints and protective coatings, especially when such materials undergo drying. Emulsions containing colloidal particles are particularly interesting as controllable test cases of such systems, but they are difficult to image because these mixtures typically scatter light strongly. We use confocal microscopy to understand full 3D picture of what happens when these emulsions dry out. Peter Lu, with Lei Xu
Phase Separation in Microgravity: When a liquid separates from a gas of the same material on earth, the denser liquid invariably sinks. In the microgravity environment of the International Space Station, however, this effect is reduced by six orders of magnitude. As a result, we can observe the spatial patterns that form in near-critical liquid-gas phase-separating mixtures for weeks, orders of magnitude longer than what can be done on earth. We work in collaboration with a number of astronauts onboard the ISS. Peter Lu
Dynamics and structure of microgel suspensions: This research focuses on the study of colloidal suspension of soft spherical particles, specifically p(NIPAm-co-AAc) microgels of diameter 1.0 – 1.5 μm. Confocal microscopy, light scattering, and particle tracking techniques are used to characterize the particles and to understand the close-packing dynamics and structure of the suspensions. Melaku Muluneh 
The role of charge interactions in colloidal gelation: Colloidal particles on the order of a micron in size make good model systems: they are small enough to behave thermally and explore phase space, yet large enough to visualize directly in a microscope, so that local as well as bulk properties can be studied. Colloids have been used in the past to model gels, but such models have typically neglected the role of electrostatic attractions in gel formation. Emily Russell 
Bulk Melting of Colloidal Wigner Crystals: Electrically charged particles in a nonpolar solvent experience long-range repulsion, leading them to form crystalline ordering at low volume fractions: colloidal Wigner crystals. I am starting a new project to investigate this system, and in particular the coexistence between the crystal phase and the fluid phase. Emily Russell 
Soft matter physics of food: Most edible materials can be viewed from a soft matter physics perspective. In the fall of 2010 I was the Head Teaching Fellow for the Science and Cooking course, and since then I have explored several different collaborations between chefs, scientists, and students. Some of these examples include chocolate, baking, and cocktails. Naveen Sinha 
Nanoformulations: Most pharmaceutical compounds which have been developed over past decade are poorly soluble in water and therefore dissolve slowly in water. This is problematic because many of these drugs are delivered orally; their slow dissolution rates lead to slow adsorption in the gastrointestinal tract and poor bioavailabilities. We are developing new technologies for enhancing the dissolution rates of poorly water-soluble drugs. Jim Wilking 
Filamentous DOX-loaded micelles: For cancer therapy, optimization of the carrier features is necessary to effectively deliver the targeting agents to tumor site. The results of in vivo antitumor activity demonstrate that the filamentous DOX-loaded micelles possess the highest safety to body and the best therapeutic effect to artificial solid tumor. Shaobing Zhou 
Shape memory polymers: Shape memory polymers (SMPs), as an emerging class of active materials, have been drawing more and more attention due to their potential applications in medicine. Among these applications, the SMPs as intelligent implants were extensively investigated to replace shape-memory alloys. Herein, the nanocomposite composed of crosslinked poly(ε-caprolactone) (c-PCL) and Fe3O4 nanoparticles represented excellent shape memory effect, triggered by an alternating magnetic field. Shaobing Zhou