Using office inkjet printer to develop paper-based electrowetting-on-dielectric micromixer based on capillary wave-induced droplet vibration mixing for the reproducibility improvement of chemiluminescence assays

Background We use inkjet printing and film adhesion methods to economically develop paper-based electrowetting-on-dielectric (EWOD) mixing device. Because the periodic shrinking and stretching of droplet contact line induces surface capillary wave, the coalesced droplet on EWOD device vibrates to accelerate solute mixing on the merged spot. Methods An office inkjet printer fabricates pads of conducting silver nanoparticles to compose EWOD activation electrodes on a piece of glossy label paper, covered with one oil-coated dielectric film. Using the triggering relays of each pad, two droplets of thirty microliter individually loaded on the electrode ends are driven to coalesce. Alloy nanorod-catalyzed chemiluminescence assay can be performed on this mixing device. Findings When ac voltage of 100 Hz is applied on the electrode flakes, compared with solute transport efficiency in static condition, solute diffusivity is enhanced by 4 times using this mixing device. Linear relation (R2 = 0.99) between luminescence intensity acquired with smartphone camera and luminol concentration of aforementioned chemiluminescence assay is obtained, demonstrating reproducibility improvement for accurate determination.