Controlled Single-Cell Compression With a High-Throughput MEMS Actuator

The electromagnetically actuated MEMS $\mu $ Hammer was used to evaluate the effects of mechanical impact on the membrane permeability, apoptotic induction, and proliferation of human neural progenitor cells. The $\mu $ Hammer enabled application of two strain magnitudes ( $\varepsilon = 42{\%}$ and 69%) for two strain durations ( $10~\mu \text{s}$ and $100~\mu \text{s}$ ) to individual cells at unprecedented high strain rates ( $\dot {\varepsilon }\mathrm { } \boldsymbol {\sim } {200\times }10^{3}\,\,\text{s}^{-1}$ ) and high throughput (up to 36,000 cells/min). This enables large numbers of cells to be analyzed and the effects of strain magnitude and duration to be decoupled. The magnitude of applied strain significantly affected cell membrane permeability shortly after compression, whereas the duration of strain significantly increased early apoptosis in cells 24 hours after compression. Strain magnitude also significantly affected cell quantity over a 70-hour period, despite no significant difference in the cell doubling times. Understanding the relationship between mechanical strain and cellular response will ultimately lead to improved diagnostics and treatment of high strain rate mechanical injury conditions such as Traumatic Brain Injury. [2020-0171]