Liquid‑handling robotics are the powerhouse behind high‑throughput labs, and behind every system are the engineers who design them. This article outlines the engineers’ basic approach to robotics design and the considerations involved in designing a liquid‑handling robot.
Understanding customer needs
Design starts with understanding the customer’s needs. Engineers typically aim to understand the workflow, the throughput, and the budget during customer consultation. A workflow is the sequence of all steps required to process a batch of samples. A workflow also defines the resources needed to process the batch. Throughput is the total number of samples that can be processed per run, and the time required to process a run. Higher throughput demands bigger robots to accommodate more resources. A larger budget allows for a bigger robot and more device options for workflow optimization.
Determining robotic size and overall layout
Once the workflow, throughput, and budget are understood, engineers can form a rough picture of the robot’s size and the layout of the worktable. A common layout places reagents and a pipetting arm on one end of a worktable, samples and trash stations in the center, and tips and a robotic gripper arm on the opposite end. This layout is mainly due to the constraints of the robotic arms. Robotic arms are mounted sequentially on a rail above the worktable. Because of this placement, a robotic arm at one end cannot access the other end of the table. Reagents and the pipetting arm are placed at one end because they do not need to be moved by the gripper arm at the other end of the worktable. Sample plates and trash stations sit in the middle because all arms need to access them frequently. Tips and the robotic gripper arm then occupy the remaining end. Although the pipetting arm cannot access the tip box at the far end of the worktable, the robotic arm can reposition it into an accessible location.
Throughput estimation
To estimate maximum throughput, engineers calculate the number of each resource required to process a batch of samples. These resources include sample plate positions, reagent volumes and reservoirs, devices, tips, and more. Engineers then consider the additional resources needed to process more batches. Each resource scales differently with sample number, but tips usually scale the fastest. Maximum throughput is determined once the worktable becomes fully occupied by resources. At this point, optimization begins to squeeze in as much throughput as possible. Optimization is where an engineer’s skill shines.
Worktable optimization
Tip space is usually the limiting factor for throughput, so various strategies are used to reduce tip footprint. One of the most effective approaches is to use stacked tip boxes. A standard tip box holds 96 tips per footprint, but stackable tip boxes allow multiple layers of 96 tips to occupy the same footprint, significantly reducing space usage. The limitation is that large‑volume tips cannot be stacked because their size requires a bulkier, non‑stackable design. Another approach to free up tip space is to use external tip‑box towers positioned beside the robot, feeding tip boxes from outside the worktable.
The choice of robotic grippers also affects accessible workspace and thus impacts throughput. Standard grippers point straight downward toward the plate from the gripper mount. Their movement paths are easier to design due to their simpler vertical clearance, but the space they can reach is somewhat limited. An offset gripper has a gripping position offset from the arm’s gripper mount. This allows the robot arm to reach sideways or move horizontally into tight, vertically stacked spaces that standard grippers cannot reach, increasing the accessible workspace. However, the L‑shaped finger design of the offset gripper can collide with nearby items, so engineers must design movement paths carefully.
There are many other clever ways to optimize space usage and pack more functions within a limited space, but I will stick to these examples for now.
Summary
Liquid‑handling robotic design starts with understanding the customer’s workflow, desired throughput, and budget. Once these factors are understood, engineers decide on the robot’s overall size and the rough layout of the arms and the worktable. They then determine the maximum throughput the worktable can support. Finally, they refine the layout to fully utilize the available space. These are the basic steps of liquid‑handling robot design.
