The separation of particles with respect to their intrinsic properties is an ongoing task in various fields such as biotechnology and recycling of electronic waste.Especially for small particles in the lower micrometer or nanometer range, separation techniques are a field of current research since many existing approaches lack either throughput or selectivity. Dielectrophoresis (DEP) is a technique that can address multiple particle properties, making it a potential candidate to solve challenging separation tasks. Currently, DEP is mostly used in microfluidic separators and thus limited in throughput. Additionally, DEP setups often require expensive components, such as electrode arrays fabricated in the clean room.Here, we present and characterize a separator based on two inexpensive customdesigned printed circuit boards (80 × 120 mm board size). The boards consist of interdigitated electrode arrays with 250 μm electrode width and spacing. We demonstrate the separation capabilities using polystyrene particles ranging from 500 nm to 6 μm in monodisperse experiments. Further, we demonstrate selective trapping at flow rates up to 240 ml∕h in the presented device for a binary mixture. Our experiments demonstrate an affordable way to increase throughput in electrode-based DEP separators.
The separation of microparticles with respect to different properties such as size and material is a research field of great interest. Dielectrophoresis, a phenomenon that is capable of addressing multiple particle properties at once, can be used to perform a chromatographic separation. However, the selectivity of current dielectrophoretic particle chromatography (DPC) techniques is limited. Here, we show a new approach for DPC based on differences in the dielectrophoretic mobilities and the crossover frequencies of polystyrene particles. Both differences are addressed by modulating the frequency of the electric field to generate positive and negative dielectrophoretic movement to achieve multiple trap-and-release cycles of the particles. A chromatographic separation of different particle sizes revealed the voltage dependency of this method. Additionally, we showed the frequency bandwidth influence on separation using one example. The DPC method developed was tested with model particles, but offers possibilities to separate a broad range of plastic and metal microparticles or cells and to overcome currently existing limitations in selectivity.
Separation of (biological) particles ($$\ll {10}~{\upmu }\text {m}$$ ≪ 10 μ m ) according to size or other properties is an ongoing challenge in a variety of technical relevant fields. Dielectrophoresis is one method to separate particles according to a diversity of properties, and within the last decades a pool of dielectrophoretic separation techniques has been developed. However, many of them either suffer selectivity or throughput. We use simulation and experiments to investigate retention mechanisms in a novel DEP scheme, namely, frequency-modulated DEP. Results from experiments and simulation show a good agreement for the separation of binary PS particles mixtures with respect to size and more importantly, for the challenging task of separating equally sized microparticles according to surface functionalization alone. The separation with respect to size was performed using 2 $${\upmu }$$ μ m and 3 $${\upmu }$$ μ m sized particles, whereas separation with respect to surface functionalization was performed with 2 $${\upmu }$$ μ m particles. The results from this study can be used to solve challenging separation tasks, for example to separate particles with distributed properties.
Lithium-ion batteries (LIBs) are common in everyday life and the demand for their raw materials is increasing. Additionally, spent LIBs should be recycled to achieve a circular economy and supply resources for new LIBs or other products. Especially the recycling of the active material of the electrodes is the focus of current research. Existing approaches for recycling (e.g., pyro-, hydrometallurgy, or flotation) still have their drawbacks, such as the loss of materials, generation of waste, or lack of selectivity. In this study, we test the behavior of commercially available LiFePO4 and two types of graphite microparticles in a dielectrophoretic high-throughput filter. Dielectrophoresis is a volume-dependent electrokinetic force that is commonly used in microfluidics but recently also for applications that focus on enhanced throughput. In our study, graphite particles show significantly higher trapping than LiFePO4 particles. The results indicate that nearly pure fractions of LiFePO4 can be obtained with this technique from a mixture with graphite.
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