Fluid-Structure Interaction Analysis on Membrane Behavior of a Microfluidic Passive Valve

Computational Fluid-Structure Interaction in Microfluidics

Micro elastofluidics is a transformative branch of microfluidics, leveraging the fluid-structure interaction (FSI) at the microscale to enhance the functionality and efficiency of various microdevices. This review paper elucidates the critical role of advanced computational FSI methods in the field of micro elastofluidics. By focusing on the interplay between fluid mechanics and structural responses, these computational methods facilitate the intricate design and optimisation of microdevices such as microvalves, micropumps, and micromixers, which rely on the precise control of fluidic and structural dynamics. In addition, these computational tools extend to the development of biomedical devices, enabling precise particle manipulation and enhancing therapeutic outcomes in cardiovascular applications. Furthermore, this paper addresses the current challenges in computational FSI and highlights the necessity for further development of tools to tackle complex, time-dependent models under microfluidic environments and varying conditions. Our review highlights the expanding potential of FSI in micro elastofluidics, offering a roadmap for future research and development in this promising area.

Numerical Approaches for Recovering the Deformable Membrane Profile of Electrostatic Microdevices for Biomedical Applications

Recently, a circular symmetrical nonlinear stationary 2D differential model for biomedical micropumps, where the amplitude of the electrostatic field is locally proportional to the curvature of the membrane, was studied in detail. Starting from this, in this work, we first introduce a positive and limited function to model the dielectric properties of the material constituting the membrane according to experimental evidence which highlights that electrostatic capacitance variation occurs when the membrane deforms. Therefore, we present and discuss algebraic conditions of existence, uniqueness, and stability, even with the fringing field formulated according to the Pelesko-Driskoll theory, which is known to take these effects into account with terms characterized by reduced computational loads. These conditions, using "gold standard" numerical approaches, allow the optimal numerical recovery of the membrane profile to be achieved under different load conditions and also provide an important criterion for choosing the intended use of the device starting from the choice of the material constituting the membrane and vice versa. Finally, important insights are discussed regarding the pull-in voltage and electrostatic pressure.

Flow Regulation Performance Analysis of Microfluidic Passive Valve for High Throughput Liquid Delivery

A microfluidic passive valve (MPV) is important for precise flow control, and it determines the reliability of the microfluidic system. In this paper, a novel MPV capable of delivering a constant flow rate independently of inlet pressure changes is proposed. The flow rate of the MPV is adjusted by the difference between the fluid force on the upper surface of the valve core and the spring force. The constant flow rate of the MPV is maintained by automatically changing the size of the gap channel formed by the groove on the valve core and the baffle on the valve body. The nearly constant flow rate of the MPV is 6.26 mL/min, with a variation of 6.5% under the inlet pressure varied from 1.25 kPa to 3.5 kPa. In addition, the flow characteristics of the MPV are analyzed by numerical simulation. With the increase in the inlet pressure, the maximum velocity gradually increases, while the increment of the maximum velocity decreases. In the movement process of the valve core, the region of pressure drop becomes larger. This work has a certain reference value for the design and research of the MPVs with high throughput liquid delivery.

A Semi-Linear Elliptic Model for a Circular Membrane MEMS Device Considering the Effect of the Fringing Field

In this study, an accurate analytic semi-linear elliptic differential model for a circular membrane MEMS device, which considers the effect of the fringing field on the membrane curvature recovering, is presented. A novel algebraic condition, related to the membrane electromechanical properties, able to govern the uniqueness of the solution, is also demonstrated. Numerical results for the membrane profile, obtained by using the Shooting techniques, the Keller-Box scheme, and the III/IV Stage Lobatto IIIa formulas, have been carried out, and their performances have been compared. The convergence conditions, and the possible presence of ghost solutions, have been evaluated and discussed. Finally, a practical criterion for choosing the membrane material as a function of the MEMS specific application is presented.

A Review of Passive Constant Flow Regulators for Microfluidic Applications

This review gives an overview of passive constant flow regulators dedicated to microfluidic applications. Without external control and energy consumption, these devices deliver a constant flow rate regardless of pressure variations, making them very attractive for various microfluidic applications, including drug delivery, flow chemistry, point-of-care tests, or microdialysis. This technical review examines progress over the last three decades in the development of these flow regulators and focuses on the working principle, fabrication methods, performance, and potential applications.