Proceedings of SerbiaTrib '13

films. Carraro et al. [10] examined formation ofOTS SAMs under different ambient temperatures.They discovered when the ambient temperaturefalls below 16°C, OTS first form islands or cloudsand then films. When the ambient temperature risesabove 40°C, the films grow evenly instead offorming islands. In addition, films form morequickly at lower temperatures. The formation ofOTS monolayer on a material surface is highlysensitive to several factors, which include thedensity of surface hydroxyl groups, reactiontemperature, reaction environment, reaction time,solvent used to deposit OTS water content of thesolvent concentration of OTS, solution age,roughness of the underlying substrate andcleaning procedures after SAM deposition [11].Therefore, how to improve the adhesion and antibacterialperformance of SAMs film becomes anattractive task in order to enhance deviceapplication and reliability.2. EXPERIMENTALThe optical lenses were ultrasonicated in acetoneand then rinsed with solvent tetrahydrofuran anddeionized water and immediately dipped in the OTSsolution containing approximately 40 ml. For thepreparation of SAMs film, OTS was dissolved inalcohol and prepared to a molar concentration of10 mM, and then mix in different proportions ofantibacterial agent (10%, 50%). The test pieces wereplaced in the solution at different bath temperaturesand duration times and a drying time of 10 min. Thetest pieces were then removed and set aside for 12 hrbefore being ultrasonicated in acetone for 5 min toremove loosely bound material and rinsed indeionized water and blown dry with nitrogen gas.The molecular structure of OTS is shown in Table 1.It’s hydrophobic properties comes from terminalgroup (CH 3 ). Main composition of biocompatibilityantibacterial agent is bioflavonoid and citric acid.For the experimental investigation ofhydrophobic properties for the different surface filmson the lens, FTA contact angle equipment was usedto measure contact angle, as shown in Figure 1.Larger contact angle indicates better hydrophobicand anti-fouling properties of surfaces. Contactangles were measured on both sides of the waterdrop. Droplet profiles were captured using a videocomprising of digital frames over a period of 12seconds and transferred to a computer for anglemeasurement. The adhesion force between surfacefilms and substrates were measured using atomicforce microscopy (AFM) by scratch mode. AFMalso was used to examine topography of samplesbefore and after SAM deposition by non-contactmode.Table 1. The molecular structure of OTSSAMs Molecular formula Head group Terminal groupOTS CH 3 (CH 2 ) 17 SiCl 3 -SiCl 3 -CH 3Figure 1. Contact angle equipment3. RESULTS AND DISCUSSIONIn the contact angle analysis of variousoperation conditions, the measurement data of eachtest piece was obtained from the mean of fivemeasurements. Figure 2(a) is a photo of the contactangle for OTS material. Figure 2(b) show thecontact angle changes with various reaction timesand bathe temperatures.Contact Angle (deg)120906030(a)020 40 60 80Temperature ( o C)(b)Figure 2. Contact angles (a) experimental photo (b)comparison chart for different reaction times andtemperatures.It shows that the higher the bathe temperature,the higher the contact angle. The higher the reactiontime, the higher is the contact angle. However, thevariation of contact angles of OTS+50%antibacterial agent films under various operation13 th International Conference on Tribology – Serbiatrib’13 103