Patterning with particles using three-dimensional interdigitated array electrodes with negative dielectrophoresis and its application to simple immunosensing

Abstract

Island organization of particles have been fabricated in a microfluidic device consisted of upper and lower conductive indium-tin-oxide (ITO) substrates with interdigitated microband array (IDA) electrode used as the template based on a dielectrophoresis (DEP). Grid formation of electrodes was fabricated by rotating the upper template ITO-IDA by 90° relative to the lower ITO-IDA. A suspension of polystyrene particles with a 3-μm diameter was introduced into the device. AC electric signal (typically 20V peak-to-peak, 1.0MHz) was then applied to the bands on the upper and lower IDA, resulting in the formation of island patterns at the intersections with low electric fields. When the AC voltage with same frequency and same phase was applied to the bands on upper and lower IDA, particles were accumulated at the intersections consisted of the bands applied voltage and bands connected to the ground because the relatively lower electric fields were produced at those intersections; on contrast, the application of the AC voltage with different frequencies to the bands allowed to the formation of second pattern due to the generation of the strong electric field at the intersections applied the AC voltage with different frequencies. Moreover, it is possible to convert the second patterns reversibly by choosing the band applying the different frequencies. The particles forming the patterns were immobilized in a photoreactive hydrogel polymer. The well-ordered particles embedded in the flexible hydrogel sheet firmly were obtained by ultraviolet irradiation to the entire device with patterns. The accumulated particles were fixed through the immunoreactions between the antibody immobilized on the particle surface and analytes in the solution. The presence of the specific antigens allowed to the fixed complexes of particles. It is noted that the time required for single sensing is as short as 5min and separation steps are eliminated in the presented procedure, while we decide only the presence of target analytes above the limit of detection. We demonstrated the rapid and simple immunosensing using the aggregation of particles accumulated with DEP.