Investigation Of Biological Detection Based On Micro-Patterned Silicon Wafer

Biochips and microarrays are the development trend of biologicaldetection. For biochip fabrication, some topics are important such as theselection of suitable substrate and microarray arrangement, the reduction ofsignal interference between microarray and background. In this work, wedesigned and fabricated two kinds of silicon wafer: micro-patterned SiO₂/Siwafer and micro-patterned Au/SiO₂wafer, used as the supports of biochips.Their surface treatment, biodetection feasibility and their applications inoptical detection were explored. The research achievement as followings:1. The surface treatment and modification of the micro-patterned SiO₂/Sisilicon wafer. Concentrated H₂SO₄/H₂O₂solution, concentratedHCL/H₂O₂/H₂O solution, NH₄OH/H₂O₂/H₂O solution were used tohydrophiling the SiO₂/Si wafer. The results showed that the best treatmentsolution was H₂SO₄/H₂O₂solution, and the optimal treatment time was30minutes. For the modification of micro-patterned SiO₂/Si wafer, the covalentmethod and hydrophobization method were compared. It suggested that theformmer is superior to the latter in protein immobilization.Mercaptoundecanoic acid （MUA） was used in the modification of themicro-patterned Au/SiO₂wafer. The results of the contact angles confirmedthat MUA had connected onto the surface of the micro-patterned Au/SiO₂wafer, which could conjugate with biomolecules furthermore.2. The micro-patterned SiO₂/Si wafer and micro-patterned Au/SiO₂waferwere used in the detection of protein. For these two kinds of micro-patternedsilicon wafers, it indicated that the optimal concentration for theimmobilization of human IgG was100mg/L. In addition, a very strongfluorescence signal was found in the patterned area and a very lowfluorescence signal was found in the non-patterneded area, which illustratedthat the two kinds of micro-patterned silicon wafer could be used as thesubstrates of protein biochips. Surface elements in two kinds ofmicro-patterned silicon wafer were analysed by X-ray photoelectronspectroscopy （XPS）. The results proved that the proteins had been connectedonto the patterned area. For the detection of protein, the results indicated thatthe detection limit of these two kinds of micro-patterned wafers was10μg/L. 3. The micro-patterned SiO₂/Si wafer and micro-patterned Au/SiO₂waferwere used in the DNA detection. For both of two kinds of micro-patternedsilicon wafers, a very strong fluorescence signal was found in the patternedarea and a very low fluorescence signal was found in the non-patterneded area.This demonstrated that two kinds of micro-patterned wafers could be used inDNA detection, and the background signals could be negligible. Therefore, thetwo kinds of micro-patterned silicon wafers could be used as the substrates inDNA biochips.The detection limits of DNA for two kinds of micro-patternedsilicon wafers was investigated respectively. It showed that the DNA detectionlimit of in micro-patterned SiO₂/Si wafer was10pM, and that ofmicro-patterned Au/SiO₂wafer was100pM.4. The protein layer thicknesses on the surface of the micro-patternedSiO₂/Si wafer was analysed by ellipsometer and double-beam interferenceoptical detection system. The results of elllipsometer detection showed theaverage thickness of the protein layer on the surface of the micro-patternedSiO₂/Si wafer was4.3nm. The signals of different concentrations of rabbitanti-human IgG were detected by double-beam interference optical system.The results illustrated the increase of protein thickness on the surface of themicro-patterned SiO₂/Si wafer was about4.27nm, which was consistent withthe results of ellipsometric detection. The results indicated that themicro-patterned silicon wafer could be used in label-free optical detection.