Multiwalled carbon nanotube (MWCNT) has excellent properties in thermal and electrical conductivities, high tensile strength and surface area and low mass over volume. However, the usage is still limited due to its inert characteristic. MWCNT surface is hydrophobic and not miscible in most solvents. This work emphasize on simple and practical method of functionalization by sonication in mild acid condition. 6M of Nitric acid and Sulfuric acid mixture (Method I) and 6M of Nitric acid (Method II) were demonstrated as an oxidizing agent to introduce carboxyl functional group on MWCNTs surface. Both type of functionalization has demonstrated carboxyl formation but functionalization in acid mixture was chosen to be used for further study for aptamer immobilization. FTIR and SEM have been used to investigate the binding properties and surface morphology respectively. The functionalization time has also been studied by using dispersability test which resulted in good dispersion after 1 hour of functionalization.

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A simple technique for the fabrication of interdigitated electrode (IDEs) using conventional lithography was presented. A top-down simple lithography approach was used to fabricate a set of Interdigitated electrodes were patterned with aluminum metal. Silicon dioxide serves to isolate the electrode from the substrate. A chrome mask was proposed to complete this work. In this work, the proposed method was experimentally demonstrated by fabricating the IDEs structure 4-5μm, approximately. The dimensions of structure were determined by using scanning electron microscopy (SEM). It is a simple, easy-to-use and cost effective method and does not require complicated micro-lithography process for fabricating desired microelectrode in reproducible approach.

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MWCNT has always been implemented in biosensor device due to its excellent conductivity and large surface area. In this work, we have investigated the MWCNT deposition on glass substrate by using the spray technique instead of drop casting. The functionalized MWCNT has been dispersed in IPA and three different volume of the solution has been selected and the electrical conductance has been measured. It has been observed that with increase of solution volume, the thickness of MWCNT layer increased and the conductance increase five times with two folds of increase in solution volume. The height of the spray to the glass substrate has also been studied and the reduction in height resulted in increase of conductance due to the higher amount of solution that reached the substrate surface.