Research On Fabrication And Detection Application Of Graphene Sensors Based On Dielectrophoresis

Charge carriers of graphene are restricted in the plane which only possesses a carbon atom thickness by its unique two-dimensional structure, and the conductance of graphene is extremely sensitive to changes in the surrounding analyte because of its ultralarge specific surface area, which makes graphene a kind of ideal detection material. Dielectrophoresis technique can be utilized to deposite graphene at gold electrode pairs, which is applied to fabricate graphene sensors. The performances of three kinds of graphene sensors which detect Cu2+ in aqueous solution are compared, and the detection mechanism is also analyzed. The main content of this paper includes:(1) The structure, preparation methods, performances and application research of graphene is introduced.(2) Principle of dielectrophoresis is introduced, and dielectrophoresis force formula of graphene in alternating electric field is induced according to induced dipole moment of a typical spherical particle. It is analyzed that the magnitude of dielectrophoresis force is proportional to the gradient of square of electric field strength.(3) Distribution of potential, electric field and gradient of square of electric field is simulated based on finite element method, the result that isosceles triangle and square electrodes are contribute to deposite graphene in dielectrophoresis experiments is obtained. According to the analysis result, square and sharp corner electrode arrays are designed and fabricated using the photolithography technique.(4) The effects that electrode gap, geometric size, voltage and frequency on depositing graphene are researched in which the square and sharp corner electrode are targets of finite element simulation. The results are as follows:comparatively smaller sharp corner electrode and larger square electrode which are exerted a sinusoidal signal of 3V and 3MHz can acquire a larger dielectrophoretic force when electrode gap is equal to 2μm.(5) Three types of graphene sensors are fabricated and applied on detection of copper ions in aqueous solution using dielectrophoresis technology and mechanical exfoliation. Reduced graphene oxide-based sensor possesses fast response time and large relatively conductance change, thereby which has the best detection performance. The detection mechanism can be explained by the charge transfer between the graphene and Cu2+ solution in which water molecules and charged Cu2+ play the roles in acting as electron donors or acceptors, respectively.