Centrifugal microfluidic platforms: advanced unit operations and applications

Abstract

Centrifugal microfluidics has evolved into a mature technology. Several major diagnostic companies either have products on the market or are currently evaluating centrifugal microfluidics for product development. The fields of application are widespread and include clinical chemistry, immunodiagnostics and protein analysis, cell handling, molecular diagnostics, as well as food, water, and soil analysis. Nevertheless, new fluidic functions and applications that expand the possibilities of centrifugal microfluidics are being introduced at a high pace. In this review, we first present an up-to-date comprehensive overview of centrifugal microfluidic unit operations. Then, we introduce the term "process chain" to review how these unit operations can be combined for the automation of laboratory workflows. Such aggregation of basic functionalities enables efficient fluidic design at a higher level of integration. Furthermore, we analyze how novel, ground-breaking unit operations may foster the integration of more complex applications. Among these are the storage of pneumatic energy to realize complex switching sequences or to pump liquids radially inward, as well as the complete pre-storage and release of reagents. In this context, centrifugal microfluidics provides major advantages over other microfluidic actuation principles: the pulse-free inertial liquid propulsion provided by centrifugal microfluidics allows for closed fluidic systems that are free of any interfaces to external pumps. Processed volumes are easily scalable from nanoliters to milliliters. Volume forces can be adjusted by rotation and thus, even for very small volumes, surface forces may easily be overcome in the centrifugal gravity field which enables the efficient separation of nanoliter volumes from channels, chambers or sensor matrixes as well as the removal of any disturbing bubbles. In summary, centrifugal microfluidics takes advantage of a comprehensive set of fluidic unit operations such as liquid transport, metering, mixing and valving. The available unit operations cover the entire range of automated liquid handling requirements and enable efficient miniaturization, parallelization, and integration of assays.

Materials for Microfluidic Immunoassays: A Review

“…[48] Centrifugal microfluidic platforms can integrate many operation units by using the centrifugal force, Coriolis force, Euler force and extrinsic forces as their power. [27] Even though not yet industrialized, we believed that centrifugal microfluidics might eventually realize POC immunoassay.…”

Centrifugal Microfluidic Integrated Optical System for Sensing Pesticide Residues

“…Therefore, the development of low cost, point-of-need sensors become more eager for improving exposure assessment [2]. The microfluidic analysis platform could integrate multiple analysis procedures into a unit operation of microfluidic such as liquid transport, metering, mixing and valving [3]. This concept of micro total analysis (μTAS) has been proposed for several decades [4].…”

Optothermally actuated capillary burst valve

“…10 Conveniently, the optothermal platform is based on an external laser so that the actuation of the capillary burst valve does not complicate the microfluidic system itself. Optical actuation can easily be integrated in a centrifugal microfluidics platform, and others have used the phase change induced by optothermal actuation as a valving mechanism (see the review by Strohmeier et al 3 ). Here no phase change is involved but the bursting pressure is changed by changing the properties of the liquid.…”

“…Such valves are extensively used in centrifugal microfluidics where no external pressure source is used so that many active and passive valves have been implemented. 2,3 In this context, capillary burst valves (CBV) are attractive since the bursting pressure depends solely on the device geometry and the liquid properties. 4 In a capillary burst valve, the air-liquid meniscus is pinned by an abrupt change of geometry in a microfluidic channel.…”