Metastasis is responsible for the vast majority of cancer deaths. As the first step of metastasis, migration of tumor cells through the extracellular matrix (ECM) to the surrounding tissue is regulated by a variety of biochemical and biophysical signals in the ECM, which may even couple with each other to impose a combined effect. For example, interstitial flow—the slow convection of fluid occurring in the interstitial space of ECM—not only conjoins matrix permeability (or specific hydraulic conductivity) to provide direct mechanical cues to the resident cells through shear and normal stress, but also couples with biomolecular diffusion to induce chemotactic signals (e.g. CCR7-mediated autologous chemotaxis). Therefore, a mechanistic and quantitative understanding of the dependence of cancer cell migration on interstitial flow would require an ability to manipulate interstitial flow, matrix permeability, and bioactive molecules in the ECM without affecting other contributing factors such as stiffness and physical confinement.
The transport of soft units, such as droplets and gel particles, through porous media occurs throughout the oil industry. Understanding the mechanisms of soft-unit transport and the impact on two-phase flow structure in porous media would significantly benefit the petroleum industry and overcome knowledge gaps in the petroleum research field. In practical operations, we are limited to controlling or measuring only microscopic properties (e.g., unit size, gel stiffness, drop viscosity, pore throat size, and pore water velocity), while the quantification of macroscopic properties (e.g., the change of permeability) that influence oil recovery efficacy is challenging. Therefore, it is necessary to determine the quantitative correlation between variables at these two factors of scale. We establish this correlation by conducting multi-scale experiments and analysis.
Foams and emulsions appear in many edible food products, such as salad dressing and ice cream, as well as consumer and personal care products, such as shaving creams, cosmetics, and detergents. In addition, they are central to many technologies and industries like distillation, oil recovery, and removal of pollutants from environmental media. In many of these products and processes, microstructure and stabilization of foams and emulsions play critical roles in determining their properties and performance. However, some fundamental questions such as what the most efficient structure is in “very dry” foams and emulsions has been a longstanding problem for over a century. Moreover, as eco-friendly colloids emerge as an alternative stabilizing agent to replace traditional surfactants, how these particles can be optimally designed to stabilize foams and emulsions remains unclear. We are working on filling these knowledge gaps by conducting experiments in the microgravity environment of the ISS National Laboratory.
We apply microfluidic technology to develop a variety of functional materials at the micrometer-scale, which are useful for targeted delivery of drugs and active materials, optical display, sensing, enhanced oil recovery, and environmental bioremediation. For example, we developed uniform-sized giant unilamellar vesicles (GUVs) encapsulating a combination of drugs and nutrients for treating mitochondrial dysfunction, which correlates with chronic fatigue syndrome; we fabricated photo-responsive liquid crystal micro-shells and drops for lasing, display and sensing; we created hydrogel microparticles with various 3D shapes, from hexagonal disks and prisms to Kelvin and Weaire-Phelan structures; we developed temperature-switchable nanoparticle colloidosomes for targeted drug delivery; we developed smart, deformable microcapsules that can release surfactant in the reservoir condition for enhanced oil recovery.