Accurate powder dispensing for chemistry and materials science applications

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Hi @benjimaruyama, we own one solid dispensing solution and have tried several others. Here are my experiences:

Freeslate / Unchained (currently own)

Pros:

  • Good for small masses (as low as 0.5 mg), high precision (as good as +/-0.1 mg, easily <+/-0.5 mg).
  • SV system uses small disposable vials (4 ml) so you don’t need a lot of powder
  • Plastic SV caps are relatively cheap and don’t have artificial dispense number limits
  • Powdernium Classic can be used for larger masses
  • Near the top in terms of range of powders dispensed (50-70% of powders)
  • Can dispense into microplates or individual vials

Cons:

  • Slow. ~1 min/vial, or even slower when learning a new powder.
  • Not practical for large masses (>100 mg). Really optimized for the 1-10 mg scale.
  • Disposable plastic SV caps can break. If your robot has a service contract, sometimes Unchained will give you free replacements.
  • Hoppers have to be stored on the robot deck, which can take up a lot of space (esp. the large mass Classic hoppers).
  • Unchained robots are expensive, even at the low end (Junior)

Mettler Toledo Quantos (demo’d)

Pros:

  • Accurate dispensing. One of the best powder dispensers, but maybe not as accurate at the low end as Unchained. Precision varies a lot with powders, about +/- 0.3-1 mg, sometimes even 2-3 mg.
  • Generally very impressive hardware (hoppers) and powder range (near the top)
  • Can dispense larger masses than Unchained
  • Hoppers have RFID tags for identification and for remembering trainings

Cons:

  • Powder hoppers are expensive, larger than Unchained SV vials. Price per dispense is pretty high (see below)
  • Initially, powder hoppers were artificially limited to a set # of dispenses. Apparently things are better now and there are workarounds.
  • Cannot dispense into microplates. Mettler only offers a carousel multi vial changer.
  • (in Mettler form), have to manually change out hopper
  • You can contract with LabMan to integrate a Quantos with a multi-axis robot arm that can automatically change out powder hoppers and sample containers from a hotel (see A-Lab by Prof. Gerd. Ceder). Pricey.
  • Quantos price w/ autosampler is also quite high.

Chemspeed (demo’d and input from current users)

Pros:

  • Price can get significantly lower than Unchained, although still high
  • Negative gravimetric dispenser can move to vials/wells, saving time
  • Can dispense quite large volumes decently (100 mg - grams)
  • No dispense limits. Hopper heads are not disposable.

Cons:

  • Has trouble with a lot of powders – range of powders much lower than Unchained / Mettler
  • Cannot dispense low masses (mg), precision is worse than competitors
  • Hopper volumes are large (requiring lots of sample).
  • Dispense mechanism (screw or whisk) is not as advanced as Unchained/Mettler, prone to jamming, and can leak powder unintentionally.
  • If the gravimetric overhead dispenser misses the vial, recorded masses are inaccurate.
  • Software is pretty bad.
  • Generally, you have to optimize the dispense head and workflow for each powder, which is time consuming.
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