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The on-chip high-throughput mixing process is one of the main challenges in the preparation process in clinical diagnostics. Because of high laminar flow in micro-channel, the fluid should be disturbed by external force. This paper aims to study pulsed AC electrothermal flow and the multiphysic interaction between the fluid behavior, external electric field, temperature field and convection-diffusion field to generate perturbation effect inside the channel.

A set of numerical simulations were carried out by multiphysic interactions between the fluid behavior, external electric field, temperature field and convection-diffusion field to generate the pulsed AC electrothermal flow inside the channel. Behavior of electrode–electrolyte system is discussed using the electrical lumped circuit model.

Highly efficient temperature gradients are generated by applying pulsed electric potential over the electrodes; as a result, efficient secondary flows form inside the channel. The proposed method increases the interfacial contact area between the fluids and enhances the molecular diffusion transport phenomena. Maximum temperature rise of 4.1 K is observed in the gap between the electrodes for 0.08 S/m fluid medium, where the electric field is much stronger than elsewhere. Velocity field and concentration analysis reveal high performance perturbation effects for the mixing process. The periodic stretching and folding effects increase the interfacial contact area between the fluids by using pulsed AC electrothermal flow. Based on the results, 83 per cent mixing efficiency is achieved for 0.08 S/m fluid medium with a microchannel length of 400 µm. Both the mixing efficiency and generated temperature rise increase by increasing the fluid ionic strength.

The ability to generate low temperature rise is very important for AC electrothermally driven fluidic chips such as immunoassay chips. In the present research, a novel actuation mechanism has been proposed to generate AC electrothermal manipulation mechanism and enhance the mixing efficiency by using pulsed AC electrothermal flow.

Digital microfluidic devices have been demonstrated to have great potential for a wide range of applications. These devices need expensive photolithography process and clean room facilities, while printed circuit board (PCB) technology provides high configurability and at low cost. This study aims to investigate the mechanism of electrowetting-on-a-dielectric (EWOD) on PCB by solving the multiphysics interaction between fluid droplet and electric field. The performance of system will be improved by inducing an efficient electric field inside the droplet.

To induce an electric field inside the droplet on a PCB and change the initial contact angle, the mechanism of EWOD is studied based on energy minimization method and a set of simulations are carried out by considering multiphysics interaction between the fluid droplet and external electric field. The performance of EWOD on a PCB system is investigated using different electrode structures.

Surface tension plays an efficient role in smaller sizes and can be used to move and control a fluid droplet on a surface by changing the interfacial surface tension. EWOD on a PCB system is studied. and it revealed that any change in electric field affects the droplet contact angle and as a result droplet deformation and movement. The electrode pattern is an important parameter which could change the electric potential distribution inside the droplet. Array of electrodes with square, zigzag interdigitated and crescent shapes are studied to enhance the EWOD force on a PCB substrate. Based on the results, the radial shape of the crescent electrodes keeps almost the same actuated contact line, applies uniform force on the droplet periphery and prevents the droplet from large deformation. A droplet velocity of 0.6 mm/s is achieved by exciting the crescent electrodes at 315 V. Furthermore, the behavior of system is characterized for process parameters such as actuation voltage, dielectric constant of insulator layer, fluidic material properties and the resultant velocity and contact angle. The study of contact angle distribution and droplet motion revealed that it is helpful to generate EWOD mechanism on a PCB which does not need more complicated fabrication processes.

The ability to handle and manipulate the droplets is very important for chemistry on-chip analysis such as immunoassay chips. Furthermore, a PCB-based electrowetting-on-dielectric device is of high interest because it does not need cleanroom facilities and avoids additional high-cost fabrication processes. In the present research, the EWOD mechanism is studied on a PCB by using different electrode patterns.