Diamond Tip Induced Nanocrack Formation And Its Application For Microfluidic Detection

The microfluidic chip has been applied to the rapid detection of small doses in the fields of medicine,etc.It is an integrated system that integrates sampling,mixing,detection,and analysis.However,the rapid flow of micro-liquids in the micron-scale space depends on the applied centrifugal force and other power devices,and system integration is difficult.Therefore,the micro V-groove channels are processed on the chemically stable hard and brittle material substrate by using the diamond grinding wheel micro-tip,and the nano-crack channels are processed by the normal force imprint at the V-tip of the diamond abrasive particle tip.The micro V-groove channels induces the rapid flow of micro-liquids and realizes the self-discipline movement of micro-liquids in micro-channels.It is then used for rapid detection of pathogens without centrifuge.Based on the hard and brittle solid fracture mechanics,trough the combination of finite element simulation and experimental methods,the mechanism of nano-crack formation and nano-scale model of the micro-cutting of diamond abrasive tip micro-cutting was established,and the controllable model of nano-crack channels on the surface of hard and brittle chip was analyzed in this study.Firstly,the relationship between the length and depth of the nano-crack formation and the material properties,the shape of the abrasive tip and the normal compressive stress was derived.The analysis showed that increasing the normal force and reducing the Vickers hardness of the material can increase the length and depth of the nano-crack channels.Secondly,the results of finite element simulation analysis showed that the length and depth of nano-cracks are consistent with the theoretical model.The length and depth of nano-cracks are related to the loading normal force and the properties of hard and brittle materials.Therefore,the scale model of the nano-crack channel is controllable.Later on,the experiment of inducing nano-cracks between diamond tips was consistent with the length and depth models.Hard and brittle materials with large Vickers hardness and low fracture toughness can control the nano-channel size,and the normal force needs to be between1 and 5 N.The depth of the nano-crack channels is less than 50 nm,the width is less than 150nm,and the depth-to-width ratio of the channel is about 0.2?0.3.Then,the microfluidic chip containing nano-cracks in the micro V-groove flow channel and its bottom is designed and processed.The results showed that the flowing velocity of the location with nano-cracks was 30 to 71%higher than that without nano-cracks,and the mixing rate reached 18.2?36.2 mm~2/s.Finally,the microfluidic chips with nano-crack channels,combined with loop-mediated nucleic acid isothermal amplification technology,were adopted to perform loop-mediated nucleic acid isothermal amplification detection on bacterial pathogens.The detection of Omp5gene,Hippurate hydrolase gene and Gsp L gene had high specificity.The experimental results showed that the minimum detection accuracy of the Omp5 gene of Brucella can reach 100 ag/?L and below.