Research Of Hydrophilic Coating Preparation On Polymer Microfluidic Chip Surface Based On Sol-gel Method

Polymer microfluidic chip is widely used in biological,chemical and medical field.The surface hydrophilic modification is needed on polymer microfluidic chip surface,because of the wettability on polymer surface can't meet the liquid drive demand in the microfluidic chip.Traditional surface modification methods,like plasma surface modification,have many defects,such as complicated modify process,high energy consumption,highly difference between chips,and may damage the chip surface during the modification,and so on.Therefore,the traditional surface modification methods don't apply for the surface modification of polymer microfluidic chip.The sol-gel method is used to prepare nano-coating on the surface of polymer microfluidic chip to complete the hydrophilic modification in this text,the experiment has shown that this method can solve the problems faced by the traditional modification methods effectively,and can meet the demands of polymer microfluidic chip surface modification.The concrete research content is listed as follows:?1?The solid surface wettability theory and the relational expression of contact angle on solid surface in different models were studied based on wettability models.The liquid drive principle in micro channel of microfluidic chip was studied through capillary theory,and the relationship between the liquid flow speed and the channel wettability in the rectangle microchannel was studied in detail,the conclusion that the liquid flow speed was inversely proportional to the inner contact angle of microchannel when the given liquid was flowing in the given rectangle microchannel was gotten finally.The formation mechanism of the sol and the reaction equation were studied through the hydrolysis and polycondensation processes of precursor.?2?The TiO₂ and Si O₂ sol were prepared through the sol-gel method,and two different hydrophilic coatings in different nature were manufactured by use of the dip-coating method.Firstly,the TBOT was used as the precursor,ethanol was used as solvent,and nitric acid was used as catalyst in the preparation of TiO₂ hydrophilic coating,and the contact angle of 15²0 ° and 40⁵0 ° were gotten respectively through the double complexing agent method and the none complexing agent method,the DEA and AcAc were added in the former method,and the PEG was added in the latter method.Then,the TEOS was used as the precursor,ethanol was used as solvent,and nitric acid was used as catalyst in the preparation of Si O₂ hydrophilic coating,and the contact angle of 50°⁶0° was gotten in through this method.The hydroxide radical was found on the surface of both hydrophilic coatings through experiment testing,and the more volume of the hydroxide radical existed,the better hydrophilicity the coating got,which show that the existence of hydroxide radical is the reason why the coating got hydrophilicity.?3?The hydrophilicity of the coatings was studied through the detection of the contact angle and liquidity on the surface of modified chips.Firstly,the contact angle difference between chips was studied by testing the contact angles on the surface of multiple sets of substrates,then the hydrophilicity lasting ability of the contact angle was studied through the discontinuous contact angle test,and finally the microchannel flow stability was studied by recording the time of deionized water flow through the microchannel.The experiment has shown that both hydrophilic coatings in this text had a good behavior in the index of the contact angle difference between chips and the hydrophilicity lasting ability,and had a good microchannel flow stability.Through the comparison of the data in different coatings,the conclusion can be gotten that the better index of the contact angle difference between chips,the better flow stability in microchannel,they have the positive correlation.?4?The coatings were characterized by the testing of film thickness and other features.The thickness of the coating was estimated by testing the height changes of step profiler probe moving on the partial modified chips surface,the surface profile was measured by Zygo,and the adhesion between coating and chip was measured by the grid-cutting test.The conclusion has shown that both hydrophilic coatings in this text had a nano sized thickness,the surface roughness didn't changed much before and after modified,and the adhesion level of the coatings was no less than level 2.