8-Channel pipettes have the ability to use less than all eight channels during liquid handling steps. You can instruct the OT-2 to perform transfers and other liquid handling actions using anywhere from one to all eight channels.
An 8-Channel pipette using this method can remove the need to occupy one of the pipette mounts with a Single Channel pipette that may only be needed for a few actions.
This method is intended to be employed by advanced users with some precautions. Note: This method is not officially supported and to be used at your own risk
Due to the fact that the channels of the 8-Channel pipette are mechanically linked, we cannot control the aspiration and dispense actions of individual channels. When aspirating and dispensing, all channels will be performing the same action at the same time.
The 8-Channel P300 uses 0.1 Amps per channel, but the 8-Channel P20 would use 0.075.
This method makes use of accessing the hardware controller directly, which can prove to be unstable and may not continue to be supported with later robot software updates.
When arranging the labware on the deck with the intention of using this method, you'll need to make sure that there are no labware objects taller than the targeted tip rack in the slot behind the tip rack. For example, if you plan to have a multichannel act as a single channel and assign it to use a tip rack in slot 5, labware taller than the tip rack in slot 5 should not be placed above it in slot 8. This is because the 8-Channel pipette is physically wider than a single channel, and some overhang of the pipette body may impact tall labware on tip pickup.
Slots 1-3 cannot be used to house a tip rack intended for access by an 8-Channel pipette using this method: the pipette could crash into the front of the OT-2
A certain force is applied to the pipette in order to pick up tips. An 8-Channel pipette normally requires 8x the force of a Single-Channel to pick up all eight tips appropriately. In the case of using an 8-Channel to pick up fewer than eight tips, the force value will need to be modified accordingly by adjusting the number_of_tips = n value. Within the code this tip number value will be multiplied by the per_tip_pickup_current = .1 value to produce the correct tip pick up force
Example code for 8-Channel P300 (GEN2):
Change the per_tip_pickup_current from 0.1 to 0.075 if an 8-Channel P20 (GEN2) is being used
tipracks = [ctx.load_labware('opentrons_96_tiprack_300ul', '4')]
pip = ctx.load_instrument('p300_multi_gen2', 'right')
num_channels_per_pickup = 1
# (only pickup tips on front-most channel)
per_tip_pickup_current = .1
# (current required for picking up one tip, do not modify unless
# you are using a GEN2 P20 8-Channel in which case change it to
pick_up_current = num_channels_per_pickup*per_tip_pickup_current
tips_ordered = [
tip for rack in tipracks
for row in rack.rows()[
for tip in row]
tip_count = 0
tip_count += 1
for i in range(len(tips_ordered)):
# perform some step