10 μm thick ultrathin glass sheet to realize a highly sensitive cantilever for precise cell stiffness measurement.

The micro-cantilever-based sensor platform has become a promising technique in the sensing area for physical, chemical and biological detection due to its portability, small size, label-free characteristics and good compatibility with "lab-on-a-chip" devices. However, traditional micro-cantilever methods are limited by their complicated fabrication, manipulation and detection, and low sensitivity. In this research, we proposed a 10 μm thick ultrathin, highly sensitive, and flexible glass cantilever integrated with a strain gauge sensor and presented its application for the measurement of single-cell mechanical properties. Compared to conventional methods, the proposed ultrathin glass sheet (UTGS)-based cantilever is easier to fabricate, has better physical and chemical properties, and shows a high linear relationship between resistance change and applied small force or displacement. The sensitivity of the cantilever is 15 μN μm and the minimum detectable displacement at the current development stage is 500 nm, which is sufficient for cell stiffness measurement. The cantilever also possesses excellent optical transparency that supports real-time observation during measurement. We first calibrated the cantilever by measuring the Young's modulus of PDMS with known specific stiffness, and then we demonstrated the measurement of oocytes and fertilized eggs in different statuses. By further optimizing the UTGS-based cantilever, we can extend its applicability to various measurements of different cells.