An AC electrothermal self-circulating system with a minimalist process to construct a biomimetic liver lobule model for drug testing

Multiphase Actuation of AC Electrothermal Micropump

Electrothermal micropumps apply an AC electric field to a conductive fluid within the range of 10 kHz-1 MHz to generate fluid flow. In this frequency range, coulombic forces dominate fluid interactions over opposing dielectric forces, resulting in high flow rates (~50-100 μm/s). To date, the electrothermal effect-using asymmetrical electrodes-has been tested only with single-phase and 2-phase actuation, while dielectrophoretic micropumps have shown improved flow rates with 3- and 4-phase actuation. Simulating muti-phase signals in COMSOL Multiphysics requires additional modules and a more involved implementation to accurately represent the electrothermal effect in a micropump. Here, we report detailed simulations of the electrothermal effect under multi-phase conditions, including single-phase, 2-phase, 3-phase and 4-phase actuation patterns. These computational models indicate that 2-phase actuation leads to the highest flow rate, with 3-phase resulting in a 5% reduced flow rate and 4-phase resulting in an 11% reduced flow rate compared to 2-phase. With these modifications to the simulation, various actuation patterns can later be tested in COMSOL for a range of electrokinetic techniques.

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

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.

AC Electrothermal Effect in Microfluidics: A Review

The electrothermal effect has been investigated extensively in microfluidics since the 1990s and has been suggested as a promising technique for fluid manipulations in lab-on-a-chip devices. The purpose of this article is to provide a timely overview of the previous works conducted in the AC electrothermal field to provide a comprehensive reference for researchers new to this field. First, electrokinetic phenomena are briefly introduced to show where the electrothermal effect stands, comparatively, versus other mechanisms. Then, recent advances in the electrothermal field are reviewed from different aspects and categorized to provide a better insight into the current state of the literature. Results and achievements of different studies are compared, and recommendations are made to help researchers weigh their options and decide on proper configuration and parameters.