Continuous Separation of Multiple Size Microparticles using Alternating Current Dielectrophoresis in Microfluidic Device with Acupuncture Needle Electrodes

The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.

A novel three-step approach to separate cathode components for lithium-ion battery recycling

Lithium-ion batteries(LIBs)represent efficient energy storage technology that can help to alleviate fossil fuel-based CO_(2) emissions.Presently,LIBs are being applied extensively in consumer electronics and electric vehicles,but because of limited resources,there is an urgent need for spent LIB recycling technologies.The complexity of LIBs,especially the electrode part,makes it difficult to achieve precision separations for each single component from the used electrode with low emissions.Herein,we propose a three-step treatment for the separation of cathode components.In detail,detaching of the current collector from the cathode is accomplished by the solvent method,which was found to be an ideal strategy compared with previous reports.Then,a thermal treatment is used to remove the polymer binder in the second step because we demonstrated that it is challenging to separate polyvinylidene fluoride(PVDF)from other cathode components by dissolution with N-methylpyrrolidone.The separation efficiency between the active material and conductive carbon by the polymer solution in the third step showed reasonably good results.We anticipate this work will serve as an important reference for the separation of each single electrode component in both laboratory-and industrialscale applications.Separation of binder and development of novel binders,which can be easily recycled for sustainable LIBs,are fruitful areas for further research.