Syringe dispenser for accurately placing nanoliter scale liquid droplets on surfaces.
The XYZ motion platform hardware is the OpenBuilds C-Beam Machine:
Identical NEMA-23 stepper motors with peak current of 2.8 A are used for the X, Y, and Z axes.
Motion is transmitted through 8 mm diameter lead screws with 8 mm lead.
Moving parts are connected to the lead screws using anti-backlash nuts.
Stepper motors have 200 full steps per revolution. The motors are operated with 1/16 microstepping, giving 2.5 microns of linear motion per microstep.
A 24 V Meanwell power supply is used to provide a maximum of 14.6 A current.
The SKR mini E3 V3 is used for controlling stepper motors. The board uses TMC2209 stepper drivers that are capable of driving motors up to 2.8 A. This control board has four identical stepper drivers because it is designed for use in 3D printers. Three of the stepper drivers are used to control X, Y, and Z motion. The fourth is used to control a stepper motor on a syringe pump used for liquid deposition.
The syringe pump hardware is taken from a model NE-300 pump. The syringe plunger motion is through a platform connected to a lead screw using an anti-backlash nut. The lead screw has a lead of 1.27 mm per revolution. The lead screw is turned using a stepper motor connected with a belt and pulley system giving a motor:screw revolution ratio of 28:15. The NE-300 stepper motor is a high precision NEMA-17 with 400 full steps per revolution. Using 1/16 microstepping results in linear movement of the syringe plunger of 0.1 microns per microstep.
Marlin firmware is used for motion control. The motion commands are written in G-code format and sent to the microcontroller on the control board via serial communication with an attached computer.