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Advanced Volume Control for Pipetting
Improving volume control precision and robustness in automated pipetting remains a challenge, often limited by traditional indirect methods. This project explores direct volume control by leveraging internal air pressure measurements and the ideal gas law. Key obstacles include friction, pressure oscillations, varying liquid viscosities, evaporation, and liquid retention. Collaborating with Hamilton Robotics, the goal is to develop a robust control architecture for their precision pipette (MagPip) suitable for diverse liquids. The approach involves mathematical modeling based on sensor data, designing robust control strategies to handle nonlinearities and disturbances, and validating through simulation and real-world experiments.
Keywords: Modeling, nonlinear control, system identification, learning-based control, state estimation, fluid dynamics
Volume control is a long-standing research problem aimed at improving the precision and robustness of automated pipetting systems. Traditional pipetting methods rely on controlling liquid volumes indirectly through plunger displacement and predefined lookup tables specific to individual liquids. In contrast, this project explores an innovative approach where the volume of liquid in the pipette tip is controlled directly by considering internal air pressure according to the ideal gas law. However, there are several challenges that need to be addressed before deploying the controller in the real-world system including technical challenges, such as stick-slip friction, Helmholtz pressure oscillations, and other physical phenomena such as highly varying viscosities, which have thus far limited the robustness of the system. Additionally, factors such as liquid evaporation—causing unpredictable changes in the air dead-volume—and liquid retention effects, characterized by thin-film formation that leaves residual liquid in pipette tips after dispensing, further complicate precise volume control.
The project is offered in collaboration with our industry partner Hamilton Robotics. It is a division of Hamilton Company, specializes in developing and manufacturing precision measurement devices and automated liquid handling workstations for the scientific community. Their product portfolio includes platforms like Microlab® VANTAGE, Microlab® STAR, Microlab® NIMBUS, and Microlab® Prep, known for their reliability, performance, and flexibility. Founded in 1950 by Clark Hamilton, the inventor of the microliter syringe, the company has grown into a global leader in laboratory automation, employing approximately 3,000 individuals worldwide.
Volume control is a long-standing research problem aimed at improving the precision and robustness of automated pipetting systems. Traditional pipetting methods rely on controlling liquid volumes indirectly through plunger displacement and predefined lookup tables specific to individual liquids. In contrast, this project explores an innovative approach where the volume of liquid in the pipette tip is controlled directly by considering internal air pressure according to the ideal gas law. However, there are several challenges that need to be addressed before deploying the controller in the real-world system including technical challenges, such as stick-slip friction, Helmholtz pressure oscillations, and other physical phenomena such as highly varying viscosities, which have thus far limited the robustness of the system. Additionally, factors such as liquid evaporation—causing unpredictable changes in the air dead-volume—and liquid retention effects, characterized by thin-film formation that leaves residual liquid in pipette tips after dispensing, further complicate precise volume control.
The project is offered in collaboration with our industry partner Hamilton Robotics. It is a division of Hamilton Company, specializes in developing and manufacturing precision measurement devices and automated liquid handling workstations for the scientific community. Their product portfolio includes platforms like Microlab® VANTAGE, Microlab® STAR, Microlab® NIMBUS, and Microlab® Prep, known for their reliability, performance, and flexibility. Founded in 1950 by Clark Hamilton, the inventor of the microliter syringe, the company has grown into a global leader in laboratory automation, employing approximately 3,000 individuals worldwide.
Mathematical Modeling: Developing a comprehensive mathematical representation of the precision pipette hardware (MagPip). Data for system identification will be acquired through pressure sensors for accurate internal air pressure measurement.
Control Architecture Design: Designing a robust control system that utilizes the mathematical model for the precision volume control subject to nonlinearities and disturbances. Several methods will be explored and compared.
Simulation and Real-world Experimentation: Implementing the controller on a real-world prototype.
Mathematical Modeling: Developing a comprehensive mathematical representation of the precision pipette hardware (MagPip). Data for system identification will be acquired through pressure sensors for accurate internal air pressure measurement. Control Architecture Design: Designing a robust control system that utilizes the mathematical model for the precision volume control subject to nonlinearities and disturbances. Several methods will be explored and compared. Simulation and Real-world Experimentation: Implementing the controller on a real-world prototype.
Muhammad Zakwan (mzakwan@ethz.ch)
Efe C. Balta (efe.balta@inspire.ch)
Muhammad Zakwan (mzakwan@ethz.ch) Efe C. Balta (efe.balta@inspire.ch)
Semester_project__Hamilton.pdf
