OT-One Accuracy and Precision

One of our goals at OpenTrons is to demonstrate that our OT-One robot can transfer a volume of liquid from one location to another with levels of accuracy comparable to a person using a manual micropipette. And because we want to provide scientists with robots to do work they'd otherwise be doing by hand, this is the baseline we aimed to hit first (spoiler: we did it!).

To test our ability to do this, we gathered data from both a human and an OT-One doing the same liquid-handling process. Given that 1 mL of water is equivalent to 1 gram of water, the simplest way to test the resulting volumes for accuracy was to weigh each transfer. We used this simple scale for these tests, and the results are catalogued below.

Over the course of several days (July 3 – 7, 2015), the OT-One completed 80 trials transferring 10 uL, and 120 trials transferring 200 uL. In parallel, our human subject manually completed 70 trials transferring 10 uL, and 60 trials transferring 200 uL. Both sets of data were analyzed to see how closely the results approached the desired weights. The table below shows the means and standard deviations of each data set.

We used a two-sided t-test to determine whether there was a significant difference between the data sets. The null hypothesis was that there was no significant difference, so therefore a p-value of over 0.05 would indicate that there was no difference between the manual and robotic samples (we would not reject the null hypothesis).

At both volumes, the t-test showed that there was no significant difference between the results from the OpenTrons robot and from the manual pipetting. The graphs below visually compare the data to once again show how similar in accuracy the OpenTrons' and the manual pipetting methods are, as well as show how close the means are to the expected value (10 uL = 0.01 g).

These data show that the OT-One can be accurately calibrated to repeatedly dispense a desired volume of liquid, and that it is as accurate and precise as a human using the same micropipette. What's more, the OT-One was able to generate the entire data set without taking a bathroom break 😉.

While the human hand will always be able to more rapidly and dexterously move a micropipette than a simple, affordable robot like OpenTrons' OT-One can, we are excited that the OT-One is able to satisfactorily substitute for a human doing certain mundane and repetitive tasks. And our robot’s performance continues to improve!