Quantitative generation of microfluidic flow by using optically driven microspheres

Microfluidic flow generation plays a fundamental role in microfluidic systems and shows potential for applications in basic biology and clinical medicine. In this study, an enabling technology is proposed to quantitatively generate microfluid flow through the automatic movement of a microsphere in liquid by using optical tweezers. A closed-loop control strategy with visual servoing feedback is introduced to achieve high precision and robustness. The theoretical solution of the generated microfluid is obtained on the basis of Stokes equations. An experimental method is proposed, and experiments are performed to verify the effectiveness of our approach. This method does not impose any dedicated fabrication of microtool, and the microfluidic flow can be dexterously adjusted by controlling the direction, speed, and distance of the microsphere from a target location. To the best of our knowledge, this is the first demonstration of optically actuating liquids through the translational movement of microspheres with closed-loop control. The proposed method will be useful in various biomedical applications needing quantitative, precise and controllable localized microfluid.