A laboratory blood test is vital for assessing a patient’s health and disease status. Advances in microfluidic technology have opened the door for on-chip blood analysis. Currently, microfluidic devices can reproduce myriad routine laboratory blood tests. Considerable progress has been made in microfluidic cytometry, blood cell separation, and characterization. Along with the usual clinical parameters, microfluidics makes it possible to determine the physical properties of blood and blood cells. We review recent advances in microfluidic systems for measuring the physical properties and biophysical characteristics of blood and blood cells. Added emphasis is placed on multifunctional platforms that combine several microfluidic technologies for effective cell characterization. The combination of hydrodynamic, optical, electromagnetic, and/or acoustic methods in a microfluidic device facilitates the precise determination of various physical properties of blood and blood cells. We analyzed the physical quantities that are measured by microfluidic devices and the parameters that are determined through these measurements. We discuss unexplored problems and present our perspectives on the long-term challenges and trends associated with the application of microfluidics in clinical laboratories. We expect the characterization of the physical properties of blood and blood cells in a microfluidic environment to be considered a standard blood test in the future.

Microfluidic-based cell handling techniques have become promising tools for biochemical applications, and many such techniques have been developed with the advancement of microfabrication technologies. A microfluidic-based platform used for biochemical analysis offers numerous benefits, including small sample consumption, massive parallelization, rapid analysis, and the capability for single-cell analysis, which are difficult to achieve in conventional cell handling methods on a large scale. It also exhibits precise spatial and temporal control of the local cellular microenvironments based on microfluidic networks in accordance to the unique fluidic phenomena of microfluidics. This review focuses on various cell handling methods that take advantage of microfluidics by classifying them in accordance to specific functions required for biochemical analyses, including (i) cell transfer, (ii) cell separation and sorting, (iii) cell immobilization, (iv) cell isolation and encapsulation, and (v) cell retrieval.

We propose a microarray-based microfluidic platform that uses a continuous single-phase flow-assisted isolation (CSFI) method to conduct multiplex analysis of reactions between co-located heteroparticles in a single-phase aqueous solution. The CSFI method is performed by consistently and continuously introducing an aqueous-phase fluid through microchannels. Hence, the unit elements of a particle pair array can be isolated without interelement cross-contamination, as they exist in independent air curtains. The formation of particle pairs with different sizes is accomplished by sequentially loading microparticles without changing the flow directions, which achieves a particle pairing efficiency up to 91%. The immunoreaction between the receptor-coated beads and the fluorescence-labeled analytes encapsulated within the hydrogels was used as a proof of concept. The analytes were diffused from the hydrogels and only treated the paired receptor-coated beads under continuous single-phase flow. Parallel monitoring of reactions on the receptor-coated beads was conducted using the CSFI method. By characterizing the operation flow rate of the CSFI method, we demonstrated the prevention of interelement cross-contamination and the enhancement of binding efficiency on receptor-coated beads. [2019-0114]