Fluid actuation and buoyancy driven oscillation by enzyme-immobilized microfluidic microcapsules.

Mimicking microorganism's locomotion and actuation under fluid is difficult to realize. To better comprehend the motility in non-living matter, self-propelled synthetic systems are being developed as a fast-growing area of research. Inspired by the self-powered enzyme micropumps where the enzyme catalysis was harnessed to create motion, herein, enzyme-immobilized microfluidic microcapsules (MCs) were used as a microscale engine to maneuver the fluid flow. The fluid actuation was tuned by various parameters such as substrate concentration, reaction rate, diameter of MCs and the population of the MCs inside the flow chamber. The same MCs, when suspended in a solution, showed buoyancy driven motility by creating oxygen bubbles via an enzymatic reaction and the velocity of the MCs was directly dependent on the number of nucleated oxygen bubbles generated on the MC surface.