This paper presents the design and development of a piezo-driven cell injection system with the fusion of force and position control. By integrating a polyvinylidene fluoride force sensor for detecting the penetration force of biological cells and a strain-gage sensor for measuring the micropipette relative position in real time, the entire cell micromanipulation system features low cost, convenient installation, and easy maintenance. The challenge of transition jerk between the force and position controller switching is reduced by introducing a weight coefficient method. An adaptive sliding mode control with parameter estimation scheme is implemented to compensate for the hysteresis nonlinearity and disturbance of the piezoelectric actuator. The injection force is controlled by realizing an incremental proportional-integral-derivative controller. The effectiveness of the developed cell injection system is experimentally verified by penetrating zebrafish embryos. The experimental results lay a foundation for the further biological manipulation research, such as the automatic batch injection of zebrafish embryos.

This paper presents the design and testing of a novel flexure-based compliant compound constant-force mechanism (CCFM). One uniqueness of the proposed mechanism lies in that it achieves both constant-force input and constant-force output, which is enabled by integrating two types of sub-mechanisms termed active and passive constant-force structures, respectively. Unlike conventional structures, the active constant-force structure allows the reduction on input force requirement and thus the enlargement of motion stroke provided that the maximum stress of the material is within allowable value. While the passive one offers a safe environmental interaction during the contact process. Analytical model of the proposed CCFM is derived which is verified by simulation study with finite element analysis (FEA). A prototype mechanism is fabricated by a 3D printer to demonstrate the performance of the proposed CCFM design. Experimental results reveal the effectiveness of the reported CCFM.

Graphical Abstract Abstract This paper presents the design and development of a novel piezo-driven cell injection system with force feedback, which overcomes the unsatisfied force interaction between the pipette needle and embryos in conventional position control. By integrating semiconductor strain-gage sensors for detecting the cell penetration force and the micropipette relative position in real time, the developed cell microinjection system features high operation speed, confident success rate, and high survival rate. The effectiveness of the developed cell injection system is experimentally verified by penetrating zebrafish embryos. The injection of 100 embryos are conducted with separate position control and force control. Results indicate that the force control enables a survival rate of 86%, which is higher than the survival rate of 82% produced by the position control in the same control environment. The experimental results quantitatively demonstrate the superiority of force control over conventional position control for the first time.

This paper presents an automatic optimization method for compliant constant force mechanisms, which eliminates the need for time-consuming parameter tuning and complex model design in the conventional design process. The proposed optimization framework is based on the finite-element analysis (FEA) and multi-objective genetic algorithm (MOGA) methods and is designed in two steps: First, the preliminary mechanism design is carried out to roughly encompass the specified constant force objective; then, the preliminary model is optimized by applying a MOGA based on FEA results. The optimized model can achieve the desired performance automatically while achieving a larger constant force stroke, which is verified by performing FEA simulations and experimental studies. The experimental results demonstrate that the designed CFMs increase the constant force stroke by 16.3% while achieving the specified design accuracy compared to the preliminary prototype.