Single-cell biophysical characterization has been widely employed for demonstrating the physiological activity and status of individual cells, or revealing the heterogeneity among various populations. It also plays an important role in the studies on cellular differentiation and pathology, as well as early clinical diagnosis and treatment. Compared to conventional biochemical schemes, the feature of scale compatibility between cell and microchannel makes microfluidics more suitable for precise microenvironment control, high-throughput manipulation, and multi-parameter label-free detection of individual cells. Therefore, microfluidics has become an important platform for single-cell characterization and analysis. This review covers the recent advances in microfluidics for characterizing the single-cell biophysical properties, and then focuses on the discussion of specific advantages, such as single-cell resolution level and high-throughput feature, offered by microfluidics. Finally, the challenges and future directions concerning the application of this scheme in clinical practices are also discussed, and a novel single-cell microdevice for multi-parameter characterization is proposed.

Contents
1 Introduction
2 Density(Mass) characterization
3 Electrical characterization
3.1 Microfluidic Coulter counter
3.2 Microfluidic impedance cytometer
4 Mechanical characterization
4.1 Optical stretcher
4.2 Electroporation-induced deformation
4.3 Structure-induced deformation
4.4 Fluid-induced deformation
5 Multi-parameter biophysical characterization
6 Conclusion and outlook