Powder dispenser - 24-well array

thingiverse

**Work in progress - hoping to increase the reproducibility; if anyone happens to print this with a resin printer, please let me know how it works out. I'm working on making tighter tolerances with more sanding or having an additional reservoir sitting on top as I'm unsure what is mostly responsible for the variations, especially within same positions. Also open to suggestions for improving the design.** Device designed to dispense powders (mainly inorganic bases) into 24-well multiwell plate arrays containing glass shell vials (8 mm diameter, 9 mm spacings). Bases are crushed with mortar and pestle and passed through a sieve if necessary, loaded onto the slide plate, scraped into the holes and equalized with the scraper; a little tap is usually needed so that the bases drop through the holes into the vials. The general idea is that the slide plate is interchangeable to provide various dispense volumes for dispensing inorganic bases in coupling reactions. This specific one was designed at 3 mm height and 3 mm diameter; when using NaHCO3, average dispense weight was of 19.17 mg (SD = 0.57, RSD% = 2.98, N = 16). Printed in PLA at a resolution of 0.06 mm (0.25 mm nozzle); no supports required, holes were cleaned with a deburring tool or torx screwdriver and interfacing parts were progressively sanded for a smooth motion and to limit powder getting in between the parts. Top and bottom part assembled using cyanoacrylate glue; M2 nuts and screw are added to the knobs and slide plate and an appropriate length of compression spring is added - spring and screw should be selected so holes align perfectly when compressed.