Integrating a Pipette Into a Robot Manipulator With Uncalibrated Vision and TCP for Liquid Handling

This paper presents a system integration approach for a 6-DoF (Degree of Freedom) collaborative robot to operate a pipette for liquid dispensing. Its technical development is three-fold. First, we designed an end-effector for holding and triggering manual pipettes. Second, we took advantage of direct teaching to specify global labware poses and planned robotic motion based on them. Third, we leveraged hand-mounted cameras and visual classifiers to predict and correct positioning errors, which allowed precisely attaching pipettes and tips without calibration. Through experiments and analysis, we confirmed that the developed system, especially the planning and visual recognition methods, could help secure high-precision and flexible liquid dispensing. The developed system is suitable for low-frequency, high-repetition biochemical liquid dispensing tasks. We expect it to promote the deployment of collaborative robots for laboratory automation and thus improve the experimental efficiency without significantly customizing a laboratory environment.
Note to Practitioners
—The proposed system helps to automate low-frequency, high-repetition biochemical experiments using a vertical articulated robot with uncalibrated hand-mounted cameras and TCP (Tool Center Point). It can be quickly deployed in tight lab spaces or beside existing automation instruments for experiments. Implementing the system does not require high-quality cameras or precise manufacturing. The system relies on software, particularly vision compensation, and the flexibility provided by unfixed racks to successfully perform pipetting tasks. We particularly recommend using collaborative robots to implement the proposed system. Collaborative robots typically meet safety requirements and do not need to be enclosed in a cage. This allows them to be deployed in the same workspace as human researchers, enabling efficient lab experiments. Human researchers can prepare tips and microwell plates and place them in front of the robot with a certain degree of freedom, which is less burdensome than traditional automatic devices that require precise placement of tips and plates in specified positions. Practitioners can view an example of the robot working with a plant phenotyping system for screening chemicals in the supplementary video.