Design of a PVDF-MFC Force Sensor for Robot-Assisted Single Cell Microinjection

Robot-assisted cell microinjection is an important approach to modern biological applications. Micro-force sensor is a crucial device to facilitate a precise injection of biological cells. Majority of existing film-based force sensors are designed as a cantilever structure for cell injection application. However, such kind of force sensor has inherent disadvantages in terms of unstable transmission of injection force, bigger puncturing wound, and operation inaccuracy. In this paper, a novel 1-D force sensor is designed by using polyvinylidene fluoride (PVDF) and macro fiber composite (MFC) films as fixed-guided beams to construct a multistage compound parallelogram flexure mechanism. It enables both capabilities of force sensing and stable cell holding. A prototype is fabricated, calibrated, and applied to crab egg embryo injection. The transverse strain effect of the fixed-guided sensing beams has been quantitatively measured by experiments. Comparison investigation reveals the great potential of MFC film over PVDF film for force sensing in cell microinjection application. The MFC force sensor offers the resolution, sensitivity, and measuring range of 0.80 mN, 1.23 mV/mN, and 100 mN, respectively. Microinjection experiments demonstrate that the developed force sensor faithfully reveals the process of cell injection and measures the puncturing force of 27 mN for crab eggs in real time.