Study On Adhesion Behavior And Ultrasonic Treatment Of E.coli On PMMA Surface

With the increase of human ocean activities,the influence of marine biofouling on marine equipments becomes more and more significant.Once being placed into the seawater,bacterial biofilm would be inevitably formed on the surface of marine facilities and eventually form macro-biofouling.For the underwater window of marine optical sensor,even the early microfouling caused by bacterial biofilm will reduce its light transmittance and affect its normal use.Anti-fouling coatings widely used in marine equipments will not only have the risk of polluting the marine environment,but also result in the shelter of optical window of sensors and then affect the measurement accuracy.Therefore,it is very necessary to investigate environmentally friendly anti-fouling measures aiming to marine optical materials.In this study,both the adhesion behavior of Escherichia coli(E.coli)onto the surface of polymethyl methacrylate(PMMA),an optical material used as the underwater window of marine sensors,and the ultrasonic removal of E.coli biofilm from PMMA surface were investigated by means of laser scanning confocal microscope(LSCM),nano-scratch instrument,and a self-made ultrasonic anti-fouling test device on the basis of orthogonal test and statistical analysis,focusing on the adhesion characteristics of E.coli bioflim and the optimal ultrasonic treatment condition.Main conclusions are as follows:(1)An ultrasonic test device was designed and made to study the adhesion characteristics and ultrasonic desorption behavior of biofilm on material surface.This device consists of a one-way flow cell device,an ultrasonic power supply,an ultrasonic piezoelectric transducer,an oscilloscope and a micro-peristaltic pump.Samples with various sizes can be installed in the one-way flow cell equipment with good water tightness.Both ultrasonic frequency and ultrasonic power can be adjustable.The resonant frequency of the ultrasonic transducer can be measured with the oscilloscope.The flow rate of liquids can be adjusted by a peristaltic pump.(2)The adhesion behavior of E.coli biofilm on the surface of PMMA is of timedependence,including three stages: weak adhesion of scattered bacteria,strong adhesion by bacteria agglomeration,and bioflim formation due to bacteria reproduction.The adsorption amount of E.coli,the binding strength of E.coli biofilm,and the transmittance of PMMA were all non-linearly positively related to the biofouling time.The removal of E.coli biofouling on the surface of PMMA should be performed within 2 days of adhesion occurrence.(3)The ultrasonic frequency plays an important role in the ultrasonic removal of E.coli biofouling from PMMA surface,as compared with ultrasonic power and ultrasonic time.Under the given conditions in this study,the optimal ultrasonic anti-biofouling treatment parameters are as follows: the ultrasonic treat time of 7 min,the ultrasonic frequency of 20 kHz,and the ultrasonic power of 40 W.