Automated Sperm Immobilization With Compensation for Sperm Intrinsic and Fluid Flow-Induced Movements

In automated sperm immobilization, motorized stages are conventional means for transporting sperm, while they are not typical devices in clinical setups. This study designs a new robotic sperm immobilization method by leveraging a micromanipulator to position a tooltip above sperm for immobilizing it without a motorized stage. The challenge arises when tooltip motion agitates the medium, leading to the passive displacement of sperm, and the sperm's intrinsic movement also complicates tooltip positioning. To address these concerns, first, a predictor is introduced to predict the sperm's intrinsic movement. Second, a model is established to describe the fluid flow and characterize the passive displacement of sperm as a function of tooltip velocity and medium parameters. Finally, an adaptive control algorithm that accounts for uncalibrated medium parameters is designed to compensate for the sperm's intrinsic movement and tooltip motion-induced sperm displacement. The stability of the control algorithm is analyzed, and the boundedness of the positioning error is proven. Experiments verified the effectiveness of the proposed method in both predicting and feedforwarding sperm's intrinsic movement and in compensating for tooltip motion-induced sperm displacement. The performance of the proposed method is comparable to existing robotic sperm immobilization methods that rely on motorized stages, while being easier to implement in clinics. With the proposed method, the system achieved a success rate of 90.9% in sperm immobilization, representing an improvement of 28.2% over the method not factoring in the sperm's intrinsic movement and 16.3% over the method not accounting for the tooltip motion-induced sperm displacement, respectively.