Microvalves for Applications in Centrifugal Microfluidics

Abstract

Centrifugal microfluidic platforms (CDs) have opened new possibilities for inexpensive point-of-care (POC) diagnostics. They are now widely used in applications requiring polymerase chain reaction steps, blood plasma separation, serial dilutions, and many other diagnostic processes. CD microfluidic devices allow a variety of complex processes to transfer onto the small disc platform that previously were carried out by individual expensive laboratory equipment requiring trained personnel. The portability, ease of operation, integration, and robustness of the CD fluidic platforms requires simple, reliable, and scalable designs to control the flow of fluids. Valves play a vital role in opening/closing of microfluidic channels to enable a precise control of the flow of fluids on a centrifugal platform. Valving systems are also critical in isolating chambers from the rest of a fluidic network at required times, in effectively directing the reagents to the target location, in serial dilutions, and in integration of multiple other processes on a single CD. In this paper, we review the various available fluidic valving systems, discuss their working principles, and evaluate their compatibility with CD fluidic platforms. We categorize the presented valving systems into either “active”, “passive”, or “hybrid”—based on their actuation mechanism that can be mechanical, thermal, hydrophobic/hydrophilic, solubility-based, phase-change, and others. Important topics such as their actuation mechanism, governing physics, variability of performance, necessary disc spin rate for valve actuation, valve response time, and other parameters are discussed. The applicability of some types of valves for specialized functions such as reagent storage, flow control, and other applications is summarized.

Development of a New Lab-on-Paper Microfluidics Platform Using Bi-Material Cantilever Actuators for ELISA on Paper

“…Additionally, the valves had long response times and required large volumes of actuation fluids. Various other valving systems for paper-based microfluidic devices have also been developed [ 24 , 25 ]. Some of them are simple [ 26 , 27 ] and self-contained [ 28 , 29 ], requiring little to no user intervention [ 23 , 30 ], whereas some user or electrical power source input is needed for other valve systems to function [ 31 , 32 , 33 ].…”

Structural Optimization Design of Microfluidic Chips Based on Fast Sequence Pair Algorithm

“…Once the position of the arrangement is incorrect, it will lead to malfunctions in the control layer. Therefore, it is necessary to reduce the number of microvalves and place them in appropriate positions [ 11 , 12 , 13 ]. Meanwhile, when the microchannel length is too long, the strong output of an external mechanical pump will affect the execution efficiency and time accuracy of biochemical experiments [ 14 , 15 , 16 ].…”

Flipping: A Valve-Free Strategy to Control Fluid Flow in Centrifugal Microfluidic Systems

“…Hydrophobic patches or localized surface coating may be involved in the design of capillary valves (19), although their implementation may significantly complicate the manufacturing process. Capillary valves may also either prematurely burst or remain closed longer than expected, e.g., due to manufacturing imperfections at the channel corners (20). Kinahan et al (21) proposed a microfluidic strategy in which flow control is ensured through dissolvable films that are necessarily single-used.…”

“…Although effective, the incorporation of such active components in a chip increases the manufacturing complexity of the centrifugal device. It stands in contrast to biomedical diagnostic applications, where the development of low-cost devices with simple microfluidics is encouraged by both end-users and manufacturers (20), (25).…”