Abstract

Deploying Magnetic Fluids in Lab-on-a-Chip Devices

Raju Ramanujan, Professor, Nanyang Technological University

The controlled manipulation of droplets suspended in a suitable fluid is of high interest because of numerous novel applications in remote and wireless control of matter in a Lab-on-a-Chip environment. Applications in the field of microfluidics include micro to picoscale volume flow control, actuation, mixing, merging and drug delivery. Many studies have reported the use of a magnetic field gradient for such applications, however, there are very few reports of the use of uniform magnetic fields for droplet manipulation. Uniform magnetic fields are much more convenient and relevant to low cost practical LoC applications compared to non-uniform fields. Hence, we have studied, by experiments and modeling, the effect of a uniform magnetic field on the water-based ferrofluid based droplets in a nonmagnetic carrier fluid within microchannels. The actuation, merging and mixing of these droplets was controlled by tuning the magnetic field, carrier fluid viscosity, channel diameter and droplet volume. The droplet size, shape was also readily tuned by the external magnetic field and shape controlled multi-functional Janus structures could be fabricated by this method. The experimental observations are in excellent agreement with the results of multi-physics simulations. The authors are grateful to the SERC, Singapore for financial support for this work through ASTAR PSF 2012 Project: 1321202078.