Numerical simulation of a tuneable reversible flow design for practical ACET devices

Abstract

Alternating Current Electrothermal (ACET) micropumps are a well-documented flow induction and mixing method. This phenomenon has significant promise as a reliable microfluidic pumping method for high conductivity biofluids, such as cerebrospinal fluid, urine, or blood. Practical implementations so far have been limited by complex designs focused on maximized flow rates, typically in only one direction at a time. This paper describes a device geometry demonstrating, and quantifying for the first time, fully reversible flow, that is, going from 100% flow in one direction to fully symmetrical 100% flow in the opposite direction. This design incorporates multiple features targeted at practical fabrication and applications. The design enables fine-tuning of flow speeds via adjustable signal strengths in a unique manner compared to traditional ACET devices. A full numerical simulation of this device has been performed within this work. Additionally, this paper reports several methods for increasing usability of ACET devices, including proposing coatings to prevent electrolysis and increase flow rates without the risk of fluid reactions, manufacturing methods for ease of handling, and specific device parameters for implementation in microdevices. The development of an ACET device that can precisely and efficiently pump and extract fluids allows for new applications in integrated biological systems and monitoring devices.

Multiphase Actuation of AC Electrothermal Micropump

“…The geometry of the channel is modeled in 2D with dimensions shown in Figure 1. In these simulations, the electrode geometry is as follows: G1 = 150 µm, W = 120 µm, G2 = 20 µm and N = 20 µm, which is in accordance with previous electrode optimization work [26]. Another optimized geometry is also shown to verify the model, with dimensions G1 = 30 µm, W = 15 µm, G2 = 5 µm and N = 1.5 µm [26].…”

“…In these simulations, the electrode geometry is as follows: G1 = 150 µm, W = 120 µm, G2 = 20 µm and N = 20 µm, which is in accordance with previous electrode optimization work [26]. Another optimized geometry is also shown to verify the model, with dimensions G1 = 30 µm, W = 15 µm, G2 = 5 µm and N = 1.5 µm [26]. The top of the channel is modeled as polydimethylsiloxane (PDMS) and the bottom of the channel is glass to reflect the fabrication process for current ACET arrays [27].…”

“…Simulations were then performed for 1-, 2-, 3-and 4-phase configurations of electrodes to compare the performance of multiphase configurations when applied to ACET flow. Results are listed for 5 V peak as a benchmark, since above this fluid can begin to react with the electrodes and damage the device [26]. However, in Figure 2, flow rates are listed up to 10 V peak to provide an idea of flow rates that may be attainable in the future with ACET [31].…”

Optimization of Planar Interdigitated Microelectrode Array for Enhanced Sensor Responses

“…The AC electrothermal effect is induced when a non-uniform alternating current (AC) passes through an electrolyte [19] and induces temperature gradients in the bulk of the fluid that causes variations in permittivity and conductivity in the process. The interaction between the non-uniform AC electric fields and the gradients in conductivity and permittivity leads to ACET microflow [20]. The temperature of the fluid during steady state can be expressed by the following equation [8].…”