Research Projects

Localized internal forces that induce complex membrane deformations are ubiquitous in biological cells. These deformations arise from mechanical forces or cytoskeletal rearrangements; however, how such forces influence cell deformation across different length scales—and how this deformation, in turn, feeds back to affect the activity of force-generating units—remains poorly understood. To investigate this, we propose using giant unilamellar vesicles (GUVs) as a minimal cell model that encapsulates chemically active Janus colloids. These colloids generate self-propulsion via diffusiophoresis and serve as synthetic analogs to mimic the localized internal forces exerted by intracellular bacterial pathogens. Through this coupling between active particles and GUVs, we aim to unravel the modes of vesicle deformation induced by active particles, as well as the reciprocal effect of membrane deformation on the collective dynamics and organization of the active particles. This proposal aims to elucidate the roles of particle activity, density, and membrane rigidity in governing the coupling between active particles and vesicle deformation. Furthermore, we seek to investigate how heterogeneity in membrane rigidity influences both the collective behavior of active particles and the resulting deformation patterns of the vesicle. With a combined experimental and computational effort, this proposal aims to develop a comprehensive framework for understanding how active forces and membrane mechanics drive shape changes in biomimetic vesicle systems. The core–shell hematite active particles, synthesized via the sol–gel route, will possess tunable activity, enabling precise control over their propulsion behavior and trajectories. Giant unilamellar vesicles (GUVs) in the pure fluid phase, composed of a single lipid species (such as DOPC or POPC) or of mixed compositions (e.g., DOPC, DPPC, and cholesterol) exhibiting distinct ordered and disordered phases, will be prepared using the inverse emulsion method. This method enables the successful encapsulation of active particles inside the vesicle, providing a controlled environment to study their interactions with the membrane. The experimental observations will provide a rich state diagram of the different membrane profiles—such as tethering, bola-like shapes, prolates, and simple membrane fluctuations—as a function of particle strength/activity, loading, and type of trajectory. The computational approach will also form an integral part of this project, employing a mesoscale explicit solvent technique. This will allow us to gain deeper insights into the coupled dynamics of active particles and membranes. Importantly, it will enable the independent investigation of the effects of chemical activity and hydrodynamic interactions—an aspect that is challenging to isolate experimentally. Further, the effect of spatial heterogeneity of the membrane on deformation will be investigated using mixed lipid compositions, which has potential applications in targeted drug delivery and the interaction of active particles with unhealthy cells. By integrating tunable magnetic self-propelled particles, engineered membrane heterogeneity, precise force quantification, and coupled dynamics modeling, this project will deliver new design principles for programmable, shape-changing soft interfaces. Overall, it will push the frontier of biomimetic soft active matter by bridging microscale propulsion, realistic boundary conditions, and real-world translational applications.