Developing Inexpensive, Open-Source Solutions to Automated Dispensing

Abstract: The addition of liquid reagents into microplates is an essential task in the modern laboratory. Micro-Pipettes can be ideal liquid dispensers for low density microtiter plates, but when approaching the density of 1536-well plates, the use of a micro-pipette to add reagents becomes less ideal. This is where the need for automated liquid handling comes into play. There are a wide variety of automated reagent dispensers on the market, but they are often prohibitively large, costly, or can require expensive consumables. Our goal was to develop an inexpensive, open-source dispenser with a small footprint that could be modified to as needed to meet specific needs within the lab. Our initial use case for this dispenser was to support automated PDL (Poly-D-Lysine) treatment of micro-titer plates, a process which benefits from having the dispenser located inside of a biosafety cabinet.

The dispenser prototype was created by modifying an existing open-source project called midTbot. This device uses a system of belts and stepper motors to control a pen plotter, capable of make pre-programmed drawings on paper. We have leveraged this motion control system and replaced the pen with a custom Arduino Uno shield connected to a Lee Valve spike and hold circuit to control commercial Lee Co. dispenser valves attached to a pressurized bottle. Instead of drawing, the automated dispenser now can make pre-programmed moves above a microtiter plate and dispense a user-specified quantity of reagent in each well. Our dispenser is controlled via G-code that can be uploaded via a simple web interface on a Wi-Fi connected computer. The 3D printed design is compact enough to fit in a laminar flow hood. With the fundamentals of the dispenser in place, our future goals are to optimize the precision of the dispenser, simplify the software and user interface, and make this open-source dispenser freely available to anyone. We are also looking into other features such as simultaneous multi-plate dispensing and automated dispenser valve QC functionality via an integrated open-source scale.