Hybrid Electrokinetic Research Of Nanoparticle Capture Based On Spiral Electrode

With the rapid development of micro-nano fabrication technology,microfluidic devices have been extensively used to achieve precise transport and placement of a variety of particles for numerous applications.So far,hydrodynamic,acoustic tweezers,optical tweezers and other techniques have proven to be an effective way to control particle motion in microchannels.Among them,electric field-driven particle manipulation may be the most popular and versatile technique because of its general applicability and adaptability as well as the ease of operation and integration into lab-on-a-chip systems.Among various electric field manipulation methods,Induced Charge Electroosmosis(ICEO)has received extensive attention due to its micro-scale flow characteristics and excellent handling properties,but less attention has been paid to ICEO-based nanoparticle operation.Based on,we propose herein a unique concept of hybrid Electrodynamics(HED)in terms of bi-phase ICEO(BICEO)actuated in a fourterminal spiral electrode array,for effective electrokinetic enrichment of fluorescent polystyrene nanoparticles on ideally polarizable metal strips.Firstly,through the double-layer charging dynamics analysis,the flow mechanism of AC electroosmosis(ACEO)and ICEO is expounded.The linear asymptotic analysis under the Debye-Hückel limit and the quasi-stationary simplification of the electric double layer will be used under the strong coupling model.The trans-scale transient problem is transformed into the steady-state problem under the weakly coupled model.The Helmholtz-Smoluchowski slip velocity formula is used to derive the formula for calculating the time-average slip velocity under the model.In addition,the stress of the nano-particles on the surface solution and the electrode surface was analyzed,and the convectiondiffusion equation of the particle group motion was determined.Secondly,the microfluidic chip is designed and the influence of key parameters of the chip on the time-average slip velocity is simulated.The chip electrode adopts a four-terminal spiral array,which can be used to achieve largescale particle aggregation.The influence of key parameters such as electrode width,gap and channel height on the average slip velocity of the electrode surface were simulated,based on the laboratory processing conditions,the chip structure parameters were established and the chip was fabricated.Then the experimental platform was builted according to the requirements of the project.At last,by alternately applying an alternating current signal between different spiral electrode terminals,AC electroosmosis and induced charge electroosmosis exist at the same time,and the position at which the electric signal is applied is changed,and the position at which the particles gather is also changed.,namely BICEO.And then,we innovatively introduce the idea of ac field-effect flow control on BICEO;by altering the combination of gating voltage sequence,not only the number of circulative particle trapping lines is doubled,but the collecting locations can be flexibly reconfigured as well.The combination of numerical simulation and experimental verification was used to study the mechanism of particle capture and the influence of the frequency and amplitude of the applied electrical signal on particle capture.