Opentrons Magnetic Block

Opentrons Magnetic Block

Overview

The Opentrons Magnetic Block is an unpowered, 96-well magnetic separator exclusively for Opentrons Flex. It uses high-strength neodymium magnets to pull magnetic beads to the side of wells, enabling supernatant removal for DNA/RNA purification, protein cleanup, immunoprecipitation, and other bead-based separation protocols.

Core value: Automate magnetic bead-based purification workflows without manual plate transfers. Combine gripper-based plate movement with magnetic separation for fully automated DNA extraction, PCR cleanup, and bead-based assays.

Platform: Opentrons Flex only (not compatible with OT-2)

When to Use

Use the Magnetic Block skill when:

• Performing DNA/RNA extraction with magnetic beads
• PCR product cleanup (AMPure, SPRIselect beads)
• Magnetic bead-based library preparation (NGS)
• Protein purification or immunoprecipitation with magnetic beads
• Cell sorting or enrichment with magnetic particles
• Any protocol requiring magnetic bead separation

Don't use when:

• Working with OT-2 robot (Magnetic Block is Flex-only)
• Need vertical bead movement within solution (block only pulls to side)
• Require heated magnetic separation
• Working without Opentrons Flex gripper

Quick Reference

Platform Requirements

Opentrons Flex only

• API version: 2.15 or later (Magnetic Block introduced)
• Gripper required: All plate movement uses gripper
• Robot type: Must specify "robotType": "Flex"

Key Characteristics

Unpowered Design

Important: The Magnetic Block is completely unpowered:

• No electronic control
• No on/off switching
• Always magnetic when plate is present
• Robot and Opentrons App are not aware of magnetic state

Implication: All control is manual through:

• Physical plate positioning (gripper movement)
• Timed delays for bead separation
• Pipetting operations

Loading the Module

from opentrons import protocol_api

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

def run(protocol: protocol_api.ProtocolContext):
    # Load Magnetic Block
    mag_block = protocol.load_module(
        module_name="magneticBlockV1",
        location="D1"
    )

    # Load compatible labware
    mag_plate = mag_block.load_labware(
        name="biorad_96_wellplate_200ul_pcr"
    )

Compatible deck slots: Any Flex slot (A1-D3) Recommended: D1, D2, or D3 (bottom row for workflow efficiency)

Compatible Labware

The Magnetic Block works with 96-well plates that fit the magnetic footprint:

Common compatible labware:

• biorad_96_wellplate_200ul_pcr
• nest_96_wellplate_100ul_pcr_full_skirt
• opentrons_96_wellplate_200ul_pcr_full_skirt
• Other 96-well PCR plates with standard footprint

Important:

• Labware must be grippable (compatible with Flex gripper)
• Wells must align with magnet positions
• Standard 96-well footprint required

Basic Magnetic Separation Workflow

Step 1: Load Sample Plate

# Start with sample plate on deck (not on magnetic block yet)
sample_plate = protocol.load_labware("biorad_96_wellplate_200ul_pcr", "C1")

# Add magnetic beads and binding buffer
pipette.transfer(10, bead_stock, sample_plate.wells())
pipette.transfer(100, binding_buffer, sample_plate.wells(), mix_after=(5, 80))

Step 2: Incubate for Binding

# Incubate to allow beads to bind target (DNA/RNA/protein)
protocol.delay(minutes=5)

# Optional: Mix during incubation (use Heater-Shaker)

Step 3: Move to Magnetic Block

# Move plate to magnetic block using gripper
protocol.move_labware(
    labware=sample_plate,
    new_location=mag_block,
    use_gripper=True
)

Step 4: Wait for Bead Separation

# Allow beads to collect at side of wells
protocol.delay(minutes=3)

# Beads are now held at well edges by magnets

Step 5: Remove Supernatant

# Pipette supernatant while beads are held by magnets
pipette.transfer(
    volume=110,
    source=sample_plate.wells(),
    dest=waste.wells(),
    new_tip="always"
)

# Beads remain in wells, held by magnetic field

Step 6: Move Off Magnetic Block

# Move plate off magnets for bead resuspension
protocol.move_labware(
    labware=sample_plate,
    new_location="C2",
    use_gripper=True
)

# Beads are now free to resuspend

Step 7: Wash and Repeat

# Add wash buffer
pipette.transfer(150, wash_buffer, sample_plate.wells())

# Mix to resuspend beads
pipette.mix(repetitions=5, volume=100, location=sample_plate.wells())

# Return to magnetic block
protocol.move_labware(sample_plate, mag_block, use_gripper=True)

# Wait for separation
protocol.delay(minutes=2)

# Remove supernatant
pipette.transfer(150, sample_plate.wells(), waste.wells(), new_tip="always")

Step 8: Elute

# Move off magnets
protocol.move_labware(sample_plate, "C2", use_gripper=True)

# Add elution buffer
pipette.transfer(50, elution_buffer, sample_plate.wells(), mix_after=(5, 30))

# Incubate
protocol.delay(minutes=2)

# Final magnetic separation
protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)

# Transfer eluate (purified product)
pipette.transfer(45, sample_plate.wells(), elution_plate.wells(), new_tip="always")

Complete DNA Extraction Protocol

# Complete automated DNA extraction workflow
def run(protocol: protocol_api.ProtocolContext):
    # Modules and labware
    mag_block = protocol.load_module("magneticBlockV1", "D1")
    sample_plate = mag_block.load_labware("biorad_96_wellplate_200ul_pcr")

    # Additional labware
    tips = protocol.load_labware("opentrons_flex_96_tiprack_1000ul", "A1")
    waste = protocol.load_trash_bin("A3")
    reagents = protocol.load_labware("nest_12_reservoir_15ml", "C2")

    # Pipette
    pipette = protocol.load_instrument("flex_8channel_1000", "left", tip_racks=[tips])

    # Reagent locations
    lysis_beads = reagents["A1"]
    wash_buffer = reagents["A2"]
    elution_buffer = reagents["A3"]

    # Samples already in plate (loaded manually or via earlier steps)

    # 1. Add lysis beads and bind DNA
    pipette.transfer(100, lysis_beads, sample_plate.columns()[0], mix_after=(5, 80))
    protocol.delay(minutes=5)

    # 2. Magnetic separation - remove lysate
    protocol.move_labware(sample_plate, mag_block, use_gripper=True)
    protocol.delay(minutes=3)
    pipette.transfer(200, sample_plate.columns()[0], waste, new_tip="always")

    # 3. First wash
    protocol.move_labware(sample_plate, "C1", use_gripper=True)
    pipette.transfer(150, wash_buffer, sample_plate.columns()[0], mix_after=(5, 100))
    protocol.move_labware(sample_plate, mag_block, use_gripper=True)
    protocol.delay(minutes=2)
    pipette.transfer(150, sample_plate.columns()[0], waste, new_tip="always")

    # 4. Second wash
    protocol.move_labware(sample_plate, "C1", use_gripper=True)
    pipette.transfer(150, wash_buffer, sample_plate.columns()[0], mix_after=(5, 100))
    protocol.move_labware(sample_plate, mag_block, use_gripper=True)
    protocol.delay(minutes=2)
    pipette.transfer(150, sample_plate.columns()[0], waste, new_tip="always")

    # 5. Dry beads
    protocol.delay(minutes=5)

    # 6. Elute DNA
    protocol.move_labware(sample_plate, "C1", use_gripper=True)
    pipette.transfer(50, elution_buffer, sample_plate.columns()[0], mix_after=(5, 30))
    protocol.delay(minutes=2)

    # 7. Final magnetic separation
    protocol.move_labware(sample_plate, mag_block, use_gripper=True)
    protocol.delay(minutes=2)

    # 8. Collect purified DNA
    elution_plate = protocol.load_labware("biorad_96_wellplate_200ul_pcr", "C3")
    pipette.transfer(45, sample_plate.columns()[0], elution_plate.columns()[0], new_tip="always")

Common Patterns

PCR Cleanup (AMPure Beads)

# Clean PCR product with AMPure beads
mag_block = protocol.load_module("magneticBlockV1", "D1")
pcr_plate = protocol.load_labware("biorad_96_wellplate_200ul_pcr", "C1")

# 1. Add beads (0.8x ratio for >300bp fragments)
pipette.transfer(40, ampure_beads, pcr_plate.wells(), mix_after=(5, 35))
protocol.delay(minutes=5)

# 2. Magnetic separation
protocol.move_labware(pcr_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)
pipette.transfer(90, pcr_plate.wells(), waste.wells())

# 3. Ethanol washes (2x)
for _ in range(2):
    pipette.transfer(150, ethanol_70, pcr_plate.wells())
    protocol.delay(seconds=30)
    pipette.transfer(150, pcr_plate.wells(), waste.wells())

# 4. Dry
protocol.delay(minutes=5)

# 5. Elute
protocol.move_labware(pcr_plate, "C2", use_gripper=True)
pipette.transfer(30, water, pcr_plate.wells(), mix_after=(5, 20))
protocol.delay(minutes=2)

# 6. Final separation and collection
protocol.move_labware(pcr_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)
pipette.transfer(25, pcr_plate.wells(), clean_plate.wells())

NGS Library Preparation

# Magnetic bead-based library prep
mag_block = protocol.load_module("magneticBlockV1", "D2")
lib_plate = mag_block.load_labware("biorad_96_wellplate_200ul_pcr")

# After adapter ligation...

# 1. Add SPRI beads for size selection (0.6x for >400bp)
pipette.transfer(30, spri_beads, lib_plate.wells(), mix_after=(5, 25))
protocol.delay(minutes=5)

# 2. Bind large fragments
protocol.move_labware(lib_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)

# 3. SAVE supernatant (contains fragments to remove)
protocol.move_labware(lib_plate, "C1", use_gripper=True)

# 4. Add more beads to supernatant (bring to 1.0x total)
pipette.transfer(20, spri_beads, lib_plate.wells(), mix_after=(5, 30))
protocol.delay(minutes=5)

# 5. Bind desired fragments
protocol.move_labware(lib_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)

# 6. Discard supernatant
pipette.transfer(100, lib_plate.wells(), waste.wells())

# 7. Wash and elute (standard protocol)

Protein Immunoprecipitation

# Magnetic bead IP
mag_block = protocol.load_module("magneticBlockV1", "D1")
ip_plate = mag_block.load_labware("biorad_96_wellplate_200ul_pcr")

# 1. Pre-coupled antibody-bead complex in wells

# 2. Add lysate
pipette.transfer(100, lysate_plate.wells(), ip_plate.wells(), mix_after=(3, 80))

# 3. Incubate (binding)
protocol.delay(minutes=30)

# 4. Wash unbound protein
for wash_num in range(3):
    protocol.move_labware(ip_plate, mag_block, use_gripper=True)
    protocol.delay(minutes=2)
    pipette.transfer(150, ip_plate.wells(), waste.wells())

    protocol.move_labware(ip_plate, "C1", use_gripper=True)
    pipette.transfer(150, wash_buffer, ip_plate.wells(), mix_after=(3, 100))

# 5. Elute bound protein
protocol.move_labware(ip_plate, "C1", use_gripper=True)
pipette.transfer(50, elution_buffer, ip_plate.wells(), mix_after=(5, 30))
protocol.delay(minutes=5)

# 6. Collect eluate
protocol.move_labware(ip_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)
pipette.transfer(45, ip_plate.wells(), analysis_plate.wells())

Integration with Other Modules

With Heater-Shaker (Heated Lysis)

# Combine heating with magnetic purification
hs_mod = protocol.load_module("heaterShakerModuleV1", "D1")
mag_block = protocol.load_module("magneticBlockV1", "D2")
sample_plate = protocol.load_labware("biorad_96_wellplate_200ul_pcr", "C1")

# 1. Heat lysis on heater-shaker
hs_mod.open_labware_latch()
protocol.move_labware(sample_plate, hs_mod, use_gripper=True)
hs_mod.close_labware_latch()
hs_mod.set_and_wait_for_temperature(56)
hs_mod.set_and_wait_for_shake_speed(1000)
protocol.delay(minutes=15)
hs_mod.deactivate_shaker()
hs_mod.deactivate_heater()
hs_mod.open_labware_latch()

# 2. Magnetic bead binding
protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)

# ... continue with washes and elution ...

With Temperature Module (Cold Elution)

# Cold elution for stability
temp_mod = protocol.load_module("temperature module gen2", "D3")
mag_block = protocol.load_module("magneticBlockV1", "D2")

# Pre-cool elution buffer
temp_mod.set_temperature(4)

# After magnetic washes...
protocol.move_labware(sample_plate, "C1", use_gripper=True)

# Add cold elution buffer
pipette.transfer(50, cold_elution, sample_plate.wells(), mix_after=(5, 30))

# Move to cold module for elution
protocol.move_labware(sample_plate, temp_mod, use_gripper=True)
protocol.delay(minutes=5)

# Final separation
protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)
pipette.transfer(45, sample_plate.wells(), storage_plate.wells())

temp_mod.deactivate()

With Thermocycler (Post-PCR Cleanup)

# PCR → Cleanup workflow
tc_mod = protocol.load_module("thermocyclerModuleV2")
mag_block = protocol.load_module("magneticBlockV1", "D2")

# Run PCR
tc_mod.close_lid()
# ... PCR cycling ...
tc_mod.set_block_temperature(4)
tc_mod.open_lid()

# Move to deck for bead addition
pcr_plate = tc_mod.labware
protocol.move_labware(pcr_plate, "C1", use_gripper=True)

# Add AMPure beads
pipette.transfer(40, ampure_beads, pcr_plate.wells(), mix_after=(5, 35))
protocol.delay(minutes=5)

# Cleanup on magnetic block
protocol.move_labware(pcr_plate, mag_block, use_gripper=True)
# ... cleanup steps ...

Best Practices

1. Allow sufficient separation time - Typically 2-5 minutes depending on bead type
2. Use gripper for all plate movements - Manual movement defeats automation purpose
3. Avoid disturbing beads when pipetting - Aspirate from opposite side of well
4. Mix thoroughly after moving off magnets - Ensure complete bead resuspension
5. Track bead volume in calculations - Account for beads when calculating total volume
6. Use consistent bead types - Different beads have different separation times
7. Plan deck layout - Position magnetic block near other modules for efficiency
8. Test separation time - Optimize delay for your specific beads and sample type
9. Don't over-dry beads - Can reduce elution efficiency
10. Validate elution volume - Leave some headroom to avoid transferring beads

Separation Time Guidelines

Typical separation times by bead type:

• AMPure/SPRIselect (DNA): 2-3 minutes
• RNAClean (RNA): 3-4 minutes
• Protein G/A beads: 2-3 minutes
• High-density beads: 1-2 minutes
• Large volume samples: 4-5 minutes

Factors affecting separation:

• Bead concentration
• Sample volume
• Viscosity
• Magnetic bead strength
• Well geometry

Recommendation: Start with 3 minutes, adjust based on visual inspection or protocol optimization.

Common Mistakes

❌ Moving plate without gripper:

# Manual movement not practical in automated protocol
protocol.move_labware(sample_plate, mag_block, use_gripper=False)
# User must manually move plate - defeats automation

✅ Correct:

protocol.move_labware(sample_plate, mag_block, use_gripper=True)

❌ Insufficient separation time:

protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(seconds=30)  # Too short - beads still in solution
pipette.transfer(100, sample_plate.wells(), waste.wells())  # Transfers beads!

✅ Correct:

protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)  # Adequate time for separation
pipette.transfer(100, sample_plate.wells(), waste.wells())

❌ Pipetting through bead pellet:

# Aspirating from center may disturb beads on side
pipette.aspirate(100, sample_plate.wells()[0])

✅ Correct:

# Aspirate from side opposite beads
pipette.aspirate(100, sample_plate.wells()[0].bottom(z=2))
# Or use touch_tip to ensure beads aren't transferred

❌ Incomplete bead resuspension:

protocol.move_labware(sample_plate, "C1", use_gripper=True)
pipette.transfer(150, wash_buffer, sample_plate.wells())  # Beads may not resuspend

✅ Correct:

protocol.move_labware(sample_plate, "C1", use_gripper=True)
pipette.transfer(150, wash_buffer, sample_plate.wells(), mix_after=(5, 100))  # Mix to resuspend

❌ Using incompatible labware:

# Deep well plates may not align with magnets properly
mag_plate = mag_block.load_labware("nest_96_wellplate_2ml_deep")

✅ Correct:

# Use standard 96-well PCR plates
mag_plate = mag_block.load_labware("biorad_96_wellplate_200ul_pcr")

Troubleshooting

Beads not separating:

• Increase separation time (try 4-5 minutes)
• Check bead type and concentration
• Verify plate is properly seated on magnetic block
• Ensure labware is compatible with magnet positions

Beads being transferred with supernatant:

• Extend separation time
• Pipette more carefully (avoid bead pellet)
• Reduce aspiration flow rate
• Leave more residual volume

Incomplete elution:

• Ensure beads are fully resuspended before elution incubation
• Mix more vigorously
• Extend elution incubation time
• Verify beads haven't dried excessively
• Use appropriate elution buffer volume

Bead clumping:

• Mix more thoroughly when resuspending
• Ensure beads are well-mixed before adding to samples
• Avoid drying beads too long
• Check bead storage conditions

Variable recovery across wells:

• Ensure consistent bead addition volumes
• Mix uniformly across all wells
• Use consistent separation times
• Check for plate positioning issues on magnetic block

Advanced Techniques

Dual-Size Selection

# Select DNA fragments within specific size range
# First selection: Remove large fragments
pipette.transfer(30, spri_beads, lib_plate.wells(), mix_after=(5, 25))  # 0.6x
protocol.delay(minutes=5)
protocol.move_labware(lib_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)

# Collect supernatant (has small + target fragments)
protocol.move_labware(lib_plate, "C1", use_gripper=True)
pipette.transfer(80, lib_plate.wells(), temp_plate.wells())

# Second selection: Bind target fragments
pipette.transfer(20, spri_beads, temp_plate.wells(), mix_after=(5, 30))  # Brings to 1.0x
protocol.delay(minutes=5)
protocol.move_labware(temp_plate, mag_block, use_gripper=True)
protocol.delay(minutes=3)

# Discard supernatant (small fragments removed)
pipette.transfer(100, temp_plate.wells(), waste.wells())

# Wash and elute target size range

Differential Elution

# Elute different targets sequentially
# After binding multiple targets to beads...

# First elution (low stringency)
pipette.transfer(50, elution_buffer_1, sample_plate.wells(), mix_after=(5, 30))
protocol.delay(minutes=2)
protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)
pipette.transfer(45, sample_plate.wells(), fraction_1_plate.wells())

# Second elution (high stringency)
protocol.move_labware(sample_plate, "C1", use_gripper=True)
pipette.transfer(50, elution_buffer_2, sample_plate.wells(), mix_after=(5, 30))
protocol.delay(minutes=2)
protocol.move_labware(sample_plate, mag_block, use_gripper=True)
protocol.delay(minutes=2)
pipette.transfer(45, sample_plate.wells(), fraction_2_plate.wells())

No Electronic Control

Remember: The Magnetic Block has no electronic interface.

This means:

• ❌ Cannot turn magnets on/off programmatically
• ❌ No status reporting to robot
• ❌ No automatic timing
• ✅ Full control through plate positioning
• ✅ Predictable, passive magnetic field
• ✅ No calibration or initialization required

Control strategy: Move plate TO block = magnets engaged, move plate OFF block = magnets disengaged

API Version Requirements

• Minimum API version: 2.15 (Magnetic Block introduced)
• Recommended: 2.19+ for full Flex feature support
• Robot type: Must be Opentrons Flex

Additional Resources

• Magnetic Block Documentation: https://docs.opentrons.com/v2/modules/magnetic_block.html
• Gripper Documentation: https://docs.opentrons.com/v2/new_protocol_api.html#opentrons.protocol_api.ProtocolContext.move_labware
• Protocol Library: https://protocols.opentrons.com/
• Opentrons Support: https://support.opentrons.com/

Related Skills

• opentrons - Main Opentrons Python API skill
• opentrons-gripper - Automated labware movement (required)
• opentrons-heater-shaker - Heated incubation with mixing
• opentrons-temperature-module - Temperature control
• opentrons-thermocycler - PCR for molecular workflows