Opentrons Python API v2

Overview

The Opentrons Python API v2 enables laboratory automation through Python protocols that control liquid handling robots (OT-2 and Flex). Write protocols that automate pipetting, temperature control, magnetic separation, plate reading, and complex multi-step workflows with reproducible precision.

Core value: Transform manual, error-prone pipetting workflows into automated, reproducible protocols. A 100-line protocol can replace hours of manual work with precise, documented liquid handling.

When to Use

Use the Opentrons skill when:

• Writing automated liquid handling protocols
• Setting up serial dilutions, plate replication, or reagent distribution
• Integrating temperature control, magnetic separation, or plate reading into workflows
• Adapting OT-2 protocols for Opentrons Flex
• Troubleshooting protocol execution or hardware integration
• Optimizing pipetting parameters (flow rates, tip positions, mixing)

Specialized subskills available:

• heater-shaker - Temperature control with orbital mixing
• absorbance-reader - Microplate spectrophotometry
• gripper - Automated labware movement (Flex only)
• thermocycler - PCR thermal cycling
• temperature-module - Precise heating/cooling (4-95°C)
• magnetic-block - Magnetic bead separation (Flex only)

Don't use when:

• Working with non-Opentrons liquid handlers
• Writing general Python code unrelated to lab automation
• You need detailed module-specific guidance (use the specialized subskills)

Robot Platforms

Opentrons Flex

Modern platform with advanced capabilities:

• Gripper for automated labware movement
• 96-channel pipetting
• Coordinate-based deck slots (A1-D3)
• Larger working volume and deck space
• Trash bin requires explicit loading (API 2.16+)
• Staging area slots in column 4

OT-2

Established platform:

• Numeric deck slots (1-12)
• Fixed trash in slot 12
• 1-channel and 8-channel pipettes
• Proven reliability for standard protocols

Both platforms use identical API syntax with platform-specific parameters.

Protocol Structure

Every Opentrons protocol follows this framework:

from opentrons import protocol_api

# 1. Metadata - Protocol identification
metadata = {
    'protocolName': 'My Protocol',
    'author': 'Name <email@example.com>',
    'description': 'Brief description of what this protocol does',
    'apiLevel': '2.19'
}

# 2. Requirements - Robot specification (Flex)
requirements = {"robotType": "Flex", "apiLevel": "2.19"}

# 3. Main function - Setup and commands
def run(protocol: protocol_api.ProtocolContext):
    # Setup: Load labware, pipettes, modules
    tips = protocol.load_labware("opentrons_flex_96_tiprack_1000ul", "A1")
    plate = protocol.load_labware("corning_96_wellplate_360ul_flat", "B1")
    pipette = protocol.load_instrument("flex_1channel_1000", "left", tip_racks=[tips])

    # Commands: Sequential robot instructions
    pipette.pick_up_tip()
    pipette.aspirate(100, plate["A1"])
    pipette.dispense(100, plate["B1"])
    pipette.drop_tip()

Key principles:

• Protocols execute completely linearly - follow line-by-line to understand robot actions
• Use descriptive variable names that mirror lab terminology
• Add comments to document workflow steps
• Group related operations logically

Core API Components

1. Loading Equipment

Labware - Plates, tubes, reservoirs:

# Load standard labware from registry
plate = protocol.load_labware("corning_96_wellplate_360ul_flat", "B1")
tips = protocol.load_labware("opentrons_flex_96_tiprack_1000ul", "A1")

# Load custom labware (JSON definition required)
custom = protocol.load_labware("custom_24_tuberack_1500ul", "C1")

Pipettes - Single, 8-channel, or 96-channel:

# Flex pipettes
left_pip = protocol.load_instrument("flex_1channel_1000", "left", tip_racks=[tips])
right_pip = protocol.load_instrument("flex_8channel_1000", "right", tip_racks=[tips])

# OT-2 pipettes
p300 = protocol.load_instrument("p300_single_gen2", "left", tip_racks=[tips])

Modules - Temperature, magnetic, thermocycler:

# Load module in specific deck slot
temp_mod = protocol.load_module("temperature module gen2", "D1")
# Load labware on module
temp_plate = temp_mod.load_labware("opentrons_96_aluminumblock_generic_pcr_strip_200ul")

Trash bin (Flex, API 2.16+):

trash = protocol.load_trash_bin("A3")

2. Accessing Wells

Individual wells:

plate["A1"]           # Single well by name
plate.wells()[0]      # First well by index
plate.wells_by_name()["A1"]  # Dictionary access

Well ranges and groups:

plate.wells()[:8]     # First row (A1-H1)
plate.rows()[0]       # All wells in row A
plate.columns()[0]    # All wells in column 1
plate.wells("A1", "H12")  # Range from A1 to H12

8-channel pipetting patterns:

# Pipette to entire column with 8-channel
pipette.transfer(100, reservoir["A1"], plate.columns()[0])

3. Liquid Handling Commands

Basic operations:

pipette.pick_up_tip()
pipette.aspirate(volume=100, location=plate["A1"], rate=1.0)
pipette.dispense(volume=100, location=plate["B1"], rate=1.0)
pipette.blow_out(location=plate["B1"])
pipette.mix(repetitions=3, volume=50, location=plate["B1"])
pipette.drop_tip()  # or pipette.return_tip()

Complex transfers:

# Single source to multiple destinations
pipette.distribute(
    volume=50,
    source=reservoir["A1"],
    dest=[plate.wells()[i] for i in range(8)],
    new_tip="once"
)

# Multiple sources to single destination (pooling)
pipette.consolidate(
    volume=20,
    source=plate.rows()[0],
    dest=reservoir["A2"],
    new_tip="always"
)

# One-to-one transfer with mixing
pipette.transfer(
    volume=100,
    source=plate.columns()[0],
    dest=plate.columns()[1],
    mix_after=(3, 50),
    new_tip="always"
)

4. Position Control

Well positions:

# Top of well (default: 1mm below top)
location = plate["A1"].top()
location = plate["A1"].top(z=-2)  # 2mm below top

# Bottom of well (default: 1mm above bottom)
location = plate["A1"].bottom()
location = plate["A1"].bottom(z=2)  # 2mm above bottom

# Center of well
location = plate["A1"].center()

Movement:

# Move to location without liquid operations
pipette.move_to(plate["A1"].top())

# Delay at current position
protocol.delay(seconds=5)
protocol.delay(minutes=2)

5. Tip Management

Flexible pickup strategies:

# Pick up from specific tip rack location
pipette.pick_up_tip(tips["A1"])

# Automatic tip tracking
pipette.pick_up_tip()  # Uses next available tip

# Reset tip tracking
tips.reset()  # Mark all tips as available again

6. Liquid Tracking

Define liquids for better protocol documentation:

# Define reagents
water = protocol.define_liquid(
    name="Water",
    description="Molecular biology grade H2O",
    display_color="#0000FF"
)

buffer = protocol.define_liquid(
    name="Lysis Buffer",
    description="10mM Tris-HCl pH 8.0",
    display_color="#00FF00"
)

# Assign liquids to wells with volumes
reservoir["A1"].load_liquid(liquid=water, volume=50000)  # 50mL
plate["A1"].load_liquid(liquid=buffer, volume=200)

7. Runtime Parameters

User-configurable variables:

def add_parameters(parameters):
    parameters.add_int(
        variable_name="sample_count",
        display_name="Number of Samples",
        description="How many samples to process",
        default=24,
        minimum=1,
        maximum=96,
        unit="samples"
    )

    parameters.add_float(
        variable_name="transfer_volume",
        display_name="Transfer Volume",
        default=50.0,
        minimum=10.0,
        maximum=200.0,
        unit="µL"
    )

def run(protocol: protocol_api.ProtocolContext):
    # Access parameters
    num_samples = protocol.params.sample_count
    vol = protocol.params.transfer_volume

Hardware Modules

Opentrons supports multiple hardware modules for specialized workflows. Each module has dedicated API methods:

Temperature Module

Precise heating/cooling (4-95°C):

temp_mod = protocol.load_module("temperature module gen2", "D1")
plate = temp_mod.load_labware("opentrons_96_aluminumblock_generic_pcr_strip_200ul")

temp_mod.set_temperature(celsius=4)  # Blocks until reached
temp_mod.deactivate()

Use the temperature-module subskill for detailed guidance.

Heater-Shaker Module

Temperature control with orbital mixing:

hs_mod = protocol.load_module("heaterShakerModuleV1", "D1")
adapter = hs_mod.load_adapter("opentrons_96_flat_bottom_adapter")
plate = adapter.load_labware("nest_96_wellplate_200ul_flat")

hs_mod.close_labware_latch()
hs_mod.set_and_wait_for_temperature(37)
hs_mod.set_and_wait_for_shake_speed(500)  # rpm
protocol.delay(minutes=5)
hs_mod.deactivate_shaker()
hs_mod.deactivate_heater()
hs_mod.open_labware_latch()

Use the heater-shaker subskill for detailed guidance including non-blocking temperature control, speed ranges, and OT-2 deck restrictions.

Thermocycler Module

PCR thermal cycling:

tc_mod = protocol.load_module("thermocyclerModuleV2")
plate = tc_mod.load_labware("opentrons_96_wellplate_200ul_pcr_full_skirt")

tc_mod.close_lid()
tc_mod.set_lid_temperature(105)
tc_mod.set_block_temperature(95, hold_time_seconds=180, block_max_volume=50)

# PCR profile
profile = [
    {"temperature": 95, "hold_time_seconds": 30},
    {"temperature": 57, "hold_time_seconds": 30},
    {"temperature": 72, "hold_time_seconds": 60}
]
tc_mod.execute_profile(steps=profile, repetitions=30, block_max_volume=50)
tc_mod.set_block_temperature(72, hold_time_minutes=5)

tc_mod.deactivate_lid()
tc_mod.deactivate_block()
tc_mod.open_lid()

Use the thermocycler subskill for detailed guidance including auto-sealing lids and advanced profiling.

Absorbance Plate Reader (Flex only)

Microplate spectrophotometry:

reader = protocol.load_module("absorbanceReaderV1", "D3")

reader.close_lid()
reader.initialize("single", [450])  # Single wavelength
reader.open_lid()

# Move plate to reader with gripper
protocol.move_labware(plate, reader, use_gripper=True)

reader.close_lid()
data = reader.read(export_filename="my_plate_data")
reader.open_lid()

# Access results
absorbance_a1 = data[450]["A1"]  # OD at 450nm for well A1

Use the absorbance-reader subskill for detailed guidance including multi-wavelength reading and data formats.

Magnetic Block (Flex only)

Magnetic bead separation:

mag_block = protocol.load_module("magneticBlockV1", "D1")
mag_plate = mag_block.load_labware("biorad_96_wellplate_200ul_pcr")

# Move plate to magnetic block with gripper
protocol.move_labware(mag_plate, mag_block, use_gripper=True)

# Wait for bead separation
protocol.delay(minutes=3)

# Pipette supernatant (beads held by magnets)
pipette.transfer(100, mag_plate["A1"], waste["A1"])

# Move plate away from magnets
protocol.move_labware(mag_plate, "C1", use_gripper=True)

Use the magnetic-block subskill for detailed guidance.

Flex-Specific Features

Gripper

Automated labware movement:

# Move labware between locations
protocol.move_labware(
    labware=plate,
    new_location="C2",
    use_gripper=True
)

# Move to module
protocol.move_labware(plate, temp_mod, use_gripper=True)

# Dispose in waste chute
protocol.move_labware(plate, protocol.load_waste_chute(), use_gripper=True)

# Move with offset adjustments
protocol.move_labware(
    plate,
    "D2",
    use_gripper=True,
    pick_up_offset={"x": 0, "y": 0, "z": 2},
    drop_offset={"x": 0, "y": 0, "z": 1}
)

Important: Open module lids/latches before gripper movement (e.g., tc_mod.open_lid(), hs_mod.open_labware_latch()).

Use the gripper subskill for detailed guidance.

96-Channel Pipetting

Full-plate transfers in single operations:

pipette_96 = protocol.load_instrument("flex_96channel_1000", "left")

# Pick up entire tip rack
pipette_96.pick_up_tip()

# Transfer entire plate
pipette_96.transfer(100, source_plate.wells(), dest_plate.wells())

pipette_96.drop_tip()

Staging Area Slots

Column 4 slots (A4, B4, C4, D4) serve as staging areas for:

• Absorbance reader lid storage
• Temporary labware placement
• Gripper operations

Note: Cannot load labware in column 4 when absorbance reader is present.

Adapting OT-2 Protocols for Flex

Key changes required:

1. Update requirements:

requirements = {"robotType": "Flex", "apiLevel": "2.19"}

2. Update pipette models:

# OT-2
p300 = protocol.load_instrument("p300_single_gen2", "left")

# Flex
p1000 = protocol.load_instrument("flex_1channel_1000", "left")

3. Update tip racks:

# OT-2
tips = protocol.load_labware("opentrons_96_tiprack_300ul", "1")

# Flex
tips = protocol.load_labware("opentrons_flex_96_tiprack_1000ul", "A1")

4. Load trash bin (API 2.16+):

trash = protocol.load_trash_bin("A3")

5. Update deck slots (optional - both formats work):

# Numeric (OT-2 style, works on both)
plate = protocol.load_labware("corning_96_wellplate_360ul_flat", "1")

# Coordinate (Flex style, works on both)
plate = protocol.load_labware("corning_96_wellplate_360ul_flat", "D1")

Common Patterns

Serial Dilution

def serial_dilution(pipette, source, destinations, dilution_factor, volume):
    """Perform serial dilution across wells."""
    # Transfer from source to first destination
    pipette.transfer(volume, source, destinations[0])

    # Serial transfers with mixing
    for i in range(len(destinations) - 1):
        pipette.transfer(
            volume / dilution_factor,
            destinations[i],
            destinations[i + 1],
            mix_after=(3, volume / 2)
        )

# Use pattern
serial_dilution(
    pipette=p1000,
    source=reservoir["A1"],
    destinations=plate.rows()[0],  # Row A
    dilution_factor=2,
    volume=100
)

Plate Replication

# Replicate entire plate
pipette.transfer(
    volume=50,
    source=source_plate.wells(),
    dest=dest_plate.wells(),
    new_tip="always"
)

Cherry Picking

# Transfer specific wells
source_wells = [source_plate["A1"], source_plate["C3"], source_plate["E5"]]
dest_wells = [dest_plate["B2"], dest_plate["D4"], dest_plate["F6"]]

pipette.transfer(100, source_wells, dest_wells, new_tip="always")

Reagent Distribution

# Distribute from reservoir to plate
pipette.distribute(
    volume=50,
    source=reservoir["A1"],
    dest=plate.wells(),
    disposal_volume=10,  # Extra volume for blowout
    new_tip="once"
)

Best Practices

1. Use liquid tracking - Define and load liquids for better protocol documentation
2. Add runtime parameters - Make protocols configurable without editing code
3. Optimize tip usage - Use distribute/consolidate to minimize tip consumption
4. Set flow rates appropriately - Adjust for viscous or volatile liquids
5. Include delays - Allow time for mixing, settling, or temperature equilibration
6. Deactivate modules - Turn off heaters/shakers/coolers at protocol end
7. Test with simulation - Validate protocols before running on hardware
8. Document thoroughly - Use comments, metadata, and liquid definitions
9. Handle errors gracefully - Add pauses for user intervention when needed
10. Calibrate labware offsets - Ensure accurate positioning for your specific labware

Advanced Features

Conditional Logic

# Dynamic protocol behavior based on parameters
if protocol.params.include_control:
    pipette.transfer(100, control_buffer, plate["A1"])

# Process only occupied wells
for well in plate.wells():
    if well.has_liquid():
        pipette.mix(3, 100, well)

Air Gaps

Prevent dripping between wells:

pipette.aspirate(100, source_well)
pipette.air_gap(10)  # 10µL air gap
pipette.dispense(110, dest_well)

Touch Tip

Remove droplets from pipette exterior:

pipette.aspirate(100, source_well)
pipette.touch_tip(location=source_well, radius=0.8, v_offset=-2)
pipette.dispense(100, dest_well)

Blow Out

Ensure complete dispense:

pipette.aspirate(100, source_well)
pipette.dispense(100, dest_well)
pipette.blow_out(dest_well.top())

Common Mistakes

❌ Forgetting to pick up tips:

pipette.aspirate(100, plate["A1"])  # Error: no tip attached

✅ Correct:

pipette.pick_up_tip()
pipette.aspirate(100, plate["A1"])

❌ Not deactivating modules:

temp_mod.set_temperature(4)
# Protocol ends - module stays at 4°C!

✅ Correct:

temp_mod.set_temperature(4)
# ... operations ...
temp_mod.deactivate()

❌ Gripper movement with closed latch:

protocol.move_labware(plate, hs_mod, use_gripper=True)  # Error: latch closed

✅ Correct:

hs_mod.open_labware_latch()
protocol.move_labware(plate, hs_mod, use_gripper=True)
hs_mod.close_labware_latch()

❌ Wrong deck slot format for Flex: Using numeric slots without quotes may cause confusion; both work, but coordinate format is clearer:

plate = protocol.load_labware("corning_96_wellplate_360ul_flat", 1)  # Works but unclear

✅ Correct:

plate = protocol.load_labware("corning_96_wellplate_360ul_flat", "D1")  # Clear

Troubleshooting

Protocol won't load:

• Check API version in requirements matches your robot firmware
• Verify labware names are correct (check Opentrons labware library)
• Ensure module loading specifies valid deck slots for your robot

Pipetting errors:

• Verify tip rack is correctly loaded and has available tips
• Check volume is within pipette range
• Ensure source/destination wells have sufficient volume/space

Module errors:

• Open lids/latches before gripper movement
• Allow modules to reach target temperature before proceeding
• Verify module is loaded in compatible deck slot

Gripper errors:

• Ensure labware is grippable (has compatible geometry)
• Check destination is accessible and not occupied
• Verify use_gripper=True is set

Installation

Protocols run on Opentrons robots via the Opentrons App. For protocol development and simulation:

pip install opentrons

Simulation:

opentrons_simulate protocol.py

Additional Resources

• Official Documentation: https://docs.opentrons.com/v2/
• Protocol Library: https://protocols.opentrons.com/
• Python API Reference: https://docs.opentrons.com/v2/new_protocol_api.html
• Labware Library: https://labware.opentrons.com/
• Support Forum: https://support.opentrons.com/
• GitHub: https://github.com/Opentrons/opentrons

Related Subskills

For detailed module-specific guidance:

• heater-shaker - Heater-Shaker Module
• absorbance-reader - Absorbance Plate Reader
• gripper - Flex Gripper
• thermocycler - Thermocycler Module
• temperature-module - Temperature Module
• magnetic-block - Magnetic Block