AC Electric Field Based Rapid Detection Of Biomolecules And Experimental Studies

Biomolecules such as pathogens,and DNA are closely related to the health status of human and animals.Infectious diseases happen frequently worldwide,thus the rapid detection of variety biomolecules is a major issue all over the world.Conventional detection includes immunoassay,optical testing,mass spectrometry,Surface-enhance Raman Scattering(SRS)and so on.However,specific equipment are required in the detection process,and the operation and maintenance also are big concerns.Also,the sample pretreatment and complicated procedures are often required.Electrochemical Impedance Spectroscopy(EIS)detection meets the demands of high sensitivity,fast response,and no labeling treatment.EIS system is easy to integrate with other devices,showing great advantages for rapid detections of biomolecules.In the conventional biomolecule detections,the motion of biomolecule relies on the diffuse,making the detection a long process.Microfluidic technologies provide a new approach for rapid biomolecule detections with low power and little amount of agents consumption.Microfluidic chips can realize fluid pumping,and manipulation of cells,proteins,necleic acids or other biomolecules at microscale.By packaging the microelectrode array and microchannel,the microfluidic chips are widely used for cell analysis,rapid diagnosis,etc.Due to size effect,the diffusion distance of biomolecules is shortened,so the detection time is reduced comparing with traditional methods.However,the laminar flow limits the convection in the microchannel.Once the AC electric field is applied on the chip,there is votex and net flow,as well as particle preconcentration caused by AC electrokinetics.The AC signal enhanced the convection and mass transfer in the microchannel,leading to an enrichment of biomolecules at specific locations within the microchannel.Thus the local concentration of targets is increased,making the rapid detection possible.This paper presents the mechanism of rapid biomolecules detections based on electric field,and numerical simulation of serum immunoassay is provided.The electric field,flow field,temperature and concentration field are coupled considering the convection and conduction,convection and mass tranfer,convection and diffusion,in order to solve the target distributions in the microchannel.There are two kinds of flow induced by AC electrid field: AC electroosmosis(ACEO)and AC electrothermal(ACET)flow.ACEO referes to the flow of low conductive fluid at low frequency while ACET related to the high conductive fluid under high frequency or low conductive fluid with an external heating or light source.The movement of polariable biomolecules referes to the posituve or negative dielectrophoresis(DEP).If the particle is easier polarized than the surrounding medium,it will experience positive DEP and be trapped to the strongest electric field regions.Conversely,the particle moves to the weakest electric field regions.The target biomolecules in the channle are delived by the swirl and flow preconcentrated,leading to the changes of electrode/fluid interface capacitance.So the rapid EIS detection of biomolecules is achieved in few minutes rather than hours or long.Experimetal studies on rapid detection of bovine Mycobacterium tuberculosis(TB)of Johne's disease,human TB,bovine progesterones are presented.Serum immunoassay is done using symmetric and asymmetric interdigitated electrode arrays.Combining simulation and experimental results,the influences of AC frequency,electrode patterns,electrode thickness and surface characteristics are analyzed and optimized.In addition,the technology can be used to study the DEP properties of biomolecules.This paper gives a theoritical and experimental studies on DEP response of p UC18 and ?DNA,and the method is verified by fluorescence experiments.Based on the analysis of rapid detection mechanism,simulation and experimental studies,we conclude that the AC electric field enhanced rapid bioparticle detection can be finished in few minutes by measuring the electrode/fluid interfacial capacitance changes.