Research | Mysite

Overview

Current research activities at our laboratory revolve around understanding the collective dynamics of self powered micro/nanomotors and also realizing their application potential towards sensing, delivery and useful energy harvesting. We study and characterize the behaviors of active materials under different experimental conditions and simultaneously develop theoretical models and simulations to gain deeper insights into the observed phenomena.

Specifically, we seek to address the following questions: Which are the most efficient mechanisms through which micro/nanomotors can uptake energy from the environment? How can motion control be established for these motors, both at the single particle and collective level, to achieve specific applications pertaining to transport and delivery? How does interparticle communication in an active assembly influence their emergent dynamics and to what degree can these behaviors be tuned on demand? What are the ranges and magnitudes of reaction induced force fields? How optimal navigation of swimmers can be achieved under noisy environments? Are there generic principles based on which active swimmers interact with their surroundings, independent of their sizes and propulsion mechanisms? And most importantly, how can these active motors be interfaced with biological systems without causing toxicities and other adverse effects?

Focus Areas

Chemically Active Systems and Transducers

We focus on the development of efficient sensing and energy harvesting platforms utilizing self-propulsion and collective behaviors of both synthetic and biological active systems. Autonomous propulsion of particles has been realized using polymer beads coated with catalytic nanoparticles that actuated in dilute hydrogen peroxide solutions. The behaviors of these self-propelled particles were found to be dependent on the properties and compositions of their surrounding media, which offered opportunities to use them for on-the-fly sensing and harvesting of useful energy in simple electrochemical chambers. Generation of electrical energy based on bacterial enzyme-mediated redox reactions has also been demonstrated, which opens avenues for the development of microbial activity controlled small-scale power generators. Our results and observations offer key insights into the foundations necessary to fabricate multifunctional sensors and energy harvesting devices based on self-powered chemically active systems.

Behavior of Enzymes and Enzyme Functionalized Motors Under Crowded and Cytoplasmic Environments

Over the years, although the co-operativity between diffusing enzymes in various intracellular signaling pathways has been well studied, the degree to which their activity plays a role in cellular mechanics has not yet been investigated. Moreover, although it has been hypothesized that localized energy transduction by enzymes was capable of generating long-ranged dynamic interactions with their surroundings, even in crowded conditions, to date, there has been no experimental studies validating such propositions. We have conducted experiments in this regard and have demonstrated that the forces generated by active enzyme molecules are strong enough to influence the dynamics of their surroundings under artificial crowded environments. In the presence of enzymatic activity not only the diffusion of the suspended particles at shorter time-scale regime enhanced, the system also showed a transition from sub-diffusive to diffusive dynamics at longer time-scale limits. Similar observations were also recorded with enzyme functionalized microparticles.

Dynamics of Bioactive Microbubbles

Self-propelled micro-/nanomotors, although offer promising platforms for biomedical applications, the fabrication of biocompatible motor designs that are capable of operating under physiological environments without causing toxic effects and damages has been a major challenge. With an aim to address this limitation, we have shown the fabrication and autonomous propulsion of catalytic microbubbles, which constitute a new class of active matter and are completely devoid of synthetic components. The catalase coated BSA shelled microbubbles demonstrate motility by harnessing energy from enzymatic reactions in substrate rich media. Being entirely made up of biological components, the motors offer a greater degree of biocompatibility with minimum retention and other adverse effects during operations. The catalytic reactions have been found to generate forces that are significant enough to induce propulsions to these bubbles, which has been measured in terms of their enhanced diffusion in solutions. This is an important contribution towards the development of smart biocompatible payload carriers in complex physiological environments. In addition, we have also shown that the bubbles prepared with native proteins are more stable than those prepared with their denatured counterparts. This is an interesting observation which has also been probed in depth to understand how changes in the protein secondary structures affect their shell formation abilities and ultimately, the lifetimes of the microbubbles.