Microbubbles as self-propelling motors

Self-powered active micro/nanomotors have gained significant research attention in the scientific community due to their unique dynamics and emergent behaviors in response to various external stimuli. In recent years, different prototypes of micro/nanomotors have been investigated extensively for various fundamental studies and useful applications. Enzyme powered motors have emerged as ideal platforms for realizing various biological applications due to their multifunctionality and specificity in operation under complex conditions. However, most enzyme powered motors developed so far suffer from issues pertaining to their integration with biological systems due to retention of their synthetic components. With an aim to design a micromotor completely devoid of non-biological components, the present study reports the fabrication of a catalase driven, bovine serum albumin shelled microbubble motor. In substrate-rich environments, these 'active' microbubbles have been found to undergo substrate concentration dependent enhanced diffusion, just like their single enzyme counterparts. Brownian dynamics simulations have also been carried out to estimate the average force generated per catalytic turnover over the motor surface. Interestingly, it was found that these active microbubbles also possess the ability to transfer energy to their surroundings. The experiments were carried out within a three-dimensional setup that offered an advantage over the commonly used quasi two-dimensional systems, as it could enable researchers to probe micro/nanomotor dynamics and associated energy transfer profiles in more in vivo like settings.