Temperature-controlled bioprinter for cheap
Printess Pro
WHAT?
The Printess Pro is an add-on to the Printess affordable bioprinter developed by Skylar-Scott Lab. The add-on uses an embedded thermocouple in the syringe to accurately control a Peltier module that heats/cools a coolant that gets circulated through a syringe-mounted heat exchanging sleeve via a pump and reservoir at a fixed rate. This setup was able to maintain bioink’s temperature at 4–40 °C operating range with ±1 °C steady-state precision while keeping total system cost <$200.
HOW?
The Printess Pro uses a thermocouple embedded within the syringe’s plunger to close a control loop implemented via the ESP32 and Simulink. The controller controls the Peltier modules that could either heat up or cool down the coolant within the fluid loop. What was implemented in Simulink is a dynamic PD/PI controller. The ESP 32 will use a PD controller for temperature changes more than 3 Degrees where the system behaves slowly and switch to a PI structure once the temperature measured at syringe is within 3 degrees of the desired temperature.
From a hardware perspective, the heat exchanger for the Printess-Pro was designed to flood the syringe with coolant and seals with o-rings to ensure efficient heat transfer between coolant and the biomaterials inside the syringe. The heat exchanger also replaces the original syringe holder designed by Skylar-Scott Lab while maintaining syringe placement which removes the need for any firmware modification. Additionally, the heat exchanger was designed to be FDM printer friendly which was a conscious design decision made to maintain the accessibility of the open-source printer.
