We present a simple microfluidic platform that uses biocompatible ferrofluids for the controlled manipulation and rapid separation of both microparticles and live cells. This low-cost platform exploits differences in particle size, shape, and elasticity to achieve rapid and efficient separation. Using microspheres, we demonstrate size-based separation with 99% separation efficiency and sub-10-m resolution in <45 s. We also show continuous manipulation and shape-based separation of live red blood cells from sickle cells and bacteria. These initial demonstrations reveal the potential of ferromicrofluidics in significantly reducing incubation times and increasing diagnostic sensitivity in cellular assays through rapid separation and delivery of target cells to sensor arrays.ferromicrofluidics ͉ magnetic hole ͉ cell separation

We present a low-cost, flow-through nanocytometer that utilizes a colloidal suspension of non-functionalized magnetic nanoparticles for label-free manipulation and separation of microparticles. Our size-based separation is mediated by angular momentum transfer from magnetically excited ferrofluid particles to microparticles. The nanocytometer is capable of rapidly sorting and focusing two or more species, with up to 99% separation efficiency and a throughput of 3 × 10(4) particles/s per mm(2) of channel cross-section. The device is readily scalable and applicable to live cell sorting with biocompatible ferrofluids, offering competitive cytometer performance in a simple and inexpensive package.

We present a rapid and completely label-free cellular manipulation and separation scheme that employs biocompatible, water-based ferrofluids within microfluidic devices. Application of localized magnetic fields through integrated electrodes exerts strong magnetic forces on any microparticle that forms a magnetic void within the ferrofluid medium in a channel. The magnetic force on each micro-particle depends sensitively on its size (tens of pN for 2 μm diameter) and is an order of magnitude larger than what can be achieved by traditional methods, such as optical tweezers and dielectrophoresis. As such, cellular manipulation and hundreds of microns of separation can easily be accomplished within ferromicrofluidic devices on a time scale of a few seconds, even under low and moderate current values.

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