Mechanical manipulation and characterization of biological cells have wide applications in genetics, reproductive biology, and cell mechanics. This research focuses on (1) the development of enabling microrobotic systems and techniques for automated cell microinjection and in situ mechanical characterization;​ and (2) the demonstration of molecule efficacy testing and cell quality assessment with the new technologies.

Targeting high-speed cell injection for molecule screening, a first-of-its-kind automated microrobotic cell injection system is developed for injecting foreign materials (e.g., DNA, morpholinos, and proteins) into zebrafish embryos (∼1.2 mm) and mouse oocytes/embryos (∼100 µm), which overcomes the problems inherent in manual operation, such as long learning curves, human fatigue, and large variations in success rates due to poor reproducibility. Novel cell holding devices are developed for immobilizing a large number of embryos into a regular pattern, greatly facilitating sample preparation and increasing the sample preparation speed. Leveraging motion control and computer vision techniques, the microrobotic system is capable of performing robust cell injection at a high speed with high survival, success, and phenotypic rates. The mouse embryo injection system is applied to molecule testing of recombinant mitochondrial proteins. The efficacy of an anti-apoptotic Bcl-xL (∆TM) protein is, for the first time, quantitatively evaluated for enhancing the development competence of mouse embryos.

For cell quality assessment, this research develops a vision-based technique for real-time cellular force measurement and in situ mechanical characterization of individual cells during microinjection. A microfabricated elastic device and a sub-pixel computer vision tracking algorithm together resolve cellular forces at the nanonewton level. Experimental results on young and old mouse oocytes demonstrate that the in situ obtained force-deformation data can be used for mechanically distinguishing healthy mouse oocytes from those with cellular dysfunctions. This work represents the first study that quantified the mechanical difference between young and old mouse oocytes, promising a practical way for oocyte quality assessment during microinjection.