I. Introduction
The nucleus is the largest and most important organelle in eukaryotic cells, and it is also the regulatory center of cytogenetics and metabolism. It has been demonstrated that mechanical properties of the cell’s membrane and nucleus are closely related to some basic biological processes [1]. Thus, by testing and analyzing variations in the cell nucleus mechanics, some physiological and pathological processes of cells can be well inferred or evaluated [2]. Past studies have shown that the mechanical properties of the nucleus vary regularly with the cell’s physiological states [3], [4], such as development [5], differentiation [6] or transcription [2]. Moreover, the mechanics of the cell nucleus is strongly affected by some external factors such as adhesion, migration or tissue stiffness [7]. Therefore, quantitative characterization of nuclear mechanical properties is of great significance in understanding the physiological state of cells.