Research of reduced-graphene-oxide-based cardiac Troponin-I biosensor fabricated by spin-coated method

• Main Authors: Yu-Chi Chen, 陳俞齊
• Other Authors: 施文彬
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/18284354239180902416

碩士 === 國立臺灣大學 === 機械工程學研究所 === 104 === Based on the development of a heart disease detection chip, this dissertation proposed to adopt the spin-coating method to form a reduced graphene oxide thin film as the sensing material on the detection chip. The clinical diagnosis of acute coronary syndrome, ACS, is based on symptom assessment, signs of oxygen deprivation on the electrocardiogram (ECG), and increase in the myocardial enzyme concentration. Because the concentration of cardiac biomarkers is increased in the early stage of myocardial damage, the early detection and subsequent emergency treatment of patients is possible. This dissertation is a part of a larger project that is targeted at developing a biosensor chip using a two dimensional material, graphene, as the detector region in order to realize a final product that is convenient, rapid, stable, and cost-effective. Therefore, this study is emphasized on the graphene thin film preparation method as well as the uniformity control with the goal of developing and mass producing for an actual product. While several studies have already proposed to employ the graphene as the sensor region material, most teams used the method of chemical vapor deposition (CVD) followed by subsequent transferring via wet-printing to the sensor region of the chip. However, during the transfer process, defects may occur resulting from the mechanical residual stress in the graphene''s structure. Thus, this study employed the spin-coating method to prepare a graphene oxide (GO) thin film that was highly uniform. Briefly, GO was first dispersed in a solution containing water and methanol. On the side, a piranha solution and cysteamine solution were used to modify the SiO2 and Au electrode surface for the hydrophilicity. By increasing the hydrophilicity of the substrate, the coverage of the GO thin film increased from 36% to 100%. Then the spin-coating method was used to cover the GO onto the modified chips. As determined using the Optics-Type surface analyser, the thickness of the GO film was 14.4 nm, 10.2 nm, 7.2 nm, and 6.6 nm at spin rate of 2000 rpm, 3000 rpm, 4000rpm, and 5000rpm, respectively. After adopting Washo''s and Meyerhofer''s models to establish a relationship between film thickness and spin rate, a -0.905 power relationship was established. Lastly, the GO film was soaked in an L-Ascorbic acid solution for the reduction process. The reduction level was determined by Raman spectroscopy through calculating the change in the ratio of the D band and the G band. Wherein, ID/IG was 0.93 before reduction and 1.05 after reduction. The highest resistance stability was achieved by coating at 5000 rpm for three times. The resultant mean resistance value was 0.25Ω and the standard deviation/mean value was 4.3%.