Electrophoretic Separation And Detection Of Algae In Ballast Water In PEG Modified Microchannel

After the ballast water convention enters into force,the accurate deteetion of the activity of microorganisms in ballast water after treatment has become a focus of the industry.Existing detection methods of microorganisms’ activity are complicated to operate and not conducive to rapid detection.Electrophoretic separation technology can distinguish different surface characteristics of microorganisms,and provides a new idea for detection and separation of microorganisms in different living conditions.This paper proposes the use of electrophoresis technology in microfluidic chip for the separation and detection of algae in ship’s ballast water after treatment.The specific research contents of this paper are as follows:(1)In order to suppress the channel electroosmotic flow,the zeta potential of PDMS in different solutions(pure water,PBS,10%PEG)after modification with different concentrations of PEG was studied.In this paper,the surface morphology of PDMS before and after PEG modification was measured by AFM.Then,the inductive measurement system was used to obtain the zeta potential of PDMS in different solutions after modification with different concentrations of PEG.The experimental results show that PEG can modify and control the zeta potential of PDMS surface by simple physical adsorption.For the same solution,the zeta potential gradually decreased with the increase of PEG concentration and the chemost potential of PDMS surface was the largest(34mV)after 2.5%PEG modification,and the zeta potential was the smallest(8.9mV)after 10%PEG modification.The above experimental results provide a basis for selecting the appropriate PEG solution eoncentration to inhibit channel electroosmotic flow,and also lay a foundation for analyzing the electrophoretic motion behavior of algae in different survival states.(2)Sodium hypochlorite was used to simulate the actual electrolytic treatment of ballast water.The electrophoretic velocity of chaefoceros(2.8 μm),chlorella(3.3μm),dicrateria inonata(6 μm),pyramimonassp(17 μm),and platymonassp(18μm)was measured before and after sodium hypochlorite treatment.The survival status of algae after sodium hypochlorite treatment was verified by fluorescein acetate(FDA).The experimental results show that the electrophoretic velocity of algae is significantly reduced after inactivation,and the velocity of large-sized surviving microalgae is faster with 4-5 μm/s at least than that of small-sized dead microalgae.Based on the above difference in velocity,electrophoretic separation and detection of chlorella treated with sodium hypochlorite was achieved..(3)Ultraviolet light was used to simulate the UV treatment of ballast water.The electrophoretic velocity of the above five algae before and after UV treatment was measured.The survival state of algae was also verified by fluorescein acetate(FDA).The experimental results show that the small-sized algae(2.8-6μm)is inactivated at a dose of 50mJ/cm2,and the large-sized algae(17-18μm)is inactivated at a dose of 100mJ/cm2.The difference in the velocity of algae in different survival states after UV treatment is similar to that of sodium hypochlorite treatment.Based on this difference,electrophoretic separation of pyramimonassp before and after UV inactivation was achieved.It is proved that algae after UV treatment is also suitable for electrophoretic separation and detection based on microfluidic chip.(4)The relationship between algae size,algae species,velocity and survival status was studied.By fitting the relationship between the product of different size of viable algae with velocity and the velocity,the results show that there is a linear relationship between the product of the size of the living algae with the velocity and the velocity of the algae.A method for judging the survival state of algae with similar velocity and different sizes is provided.The zeta potential values of PEG-modified PDMS in different solutions in this study are helpful for the research of electro-micro and nanofluids in PEG-modified PDMS microchannels;the experimental results of algae with different size before and after inactivation is helpful to develop a technology for the portable detection of viable microorganisms in ballast water.