Simultaneous Separating And Counting Particles And Algae Under High Electric Field Gradient

There is an urgent need for size-based separation,detection and counting of objects in samples for the analysis of treated ballast water.In this paper,aiming at the shortages of traditional DC dielectrophoresis and resistive pulse sensor,such as serious joule heat caused by high voltage and limited range of particle size,simultaneous separation and counting of particles and microalgae under high electrical field gradient were carried out.The main research contents are as follows:(1)Firstly the micro fluidic chip with high electric field gradient particle separation and counting was designed,and the particle detection performance of high electric field gradient impedance pulse sensor and the particle separation performance of dielectrophoresis separation device were numerically studied.The results show that the high channel width ratio(The ratio of the width of cathode channel to that of a small orifice)increases the electric field intensity gradient,and the effect of dielectrophoresis separation and particle detection are decreased with the increase of the orifice size.Under the condition of applying 100V,when the width of the small orifice increases from 1?m to 5?m,the gradient of the electric field squared(?|E|2)decreases from 3.28× 1019 V2/m3 to 4.48×1017 V 2/m3.With a certain width,when the length of the small orifice increases from 5 ?m to 15 ?m,The maximum value of ?|E|2 is reduced by 59.1%.When the length of small orifice increases from 1?m to 5?m,the relative change of current(?I)decreases from 5.015%to 3.539%.When the height of the small orifice changes from 5 m to 10 m,The maximum value of ?|E|2 in the channel is reduced by 16%,and the?I decreases from 7.38%to 3.01%.This is because when length of the orifice is increased,the electric resistance of the orifice is increased and hence the electric potential drop inside the small orifice is increased.Thus,?|E|2 is reduced,and ?I of channel is decreased.When the width of small orifice is increased,The ratio of the width of the cathode channel to that of a small orifice is decreased,so ?|E|2 is reduced,The change of resistance caused by the particle passing through the orifice is decreased,Thus,?I of channel is decreased.(2)Experimental system was set up for the simultaneous separation and counting of particles and microalgae.The experimental results showed that the high electric field gradient can be used for separating and counting a variety of particles and microalgae of different sizes at the same time,and the accuracy of separation and detection can reach 1?m.The mixed particles with diameters of 2?m and 3?m were separated by reducing the height of the detection area.When the samples were focused to pass by the sensing orifice and no agglomeration of particles occurred,the separation efficiency exceeded 99%.This paper presents the continuous separation and counting of particles by high electric field gradient.This method has the advantages in simlpe structure,high separation precision and avoiding orifice clogging.It have some values for the fast analysis of mixed samples with complex components and have significant to develop portable instrument with microfluidic chip.