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

Operation	Method	Key Parameters
Load module	`protocol.load_module()`	`"magneticBlockV1"`, location
Move plate to block	`protocol.move_labware()`	labware, mag_block, use_gripper=True
Wait for separation	`protocol.delay()`	minutes (typically 2-5)
Pipette supernatant	`pipette.transfer()`	source, dest
Move plate off block	`protocol.move_labware()`	labware, new_location, use_gripper=True

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

python

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

python

# 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

python

# 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

python

# 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

python

# 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

python

# 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

python

# 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

python

# 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

python

# 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

python

# 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)

python

# 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

python

# 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

python

# 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)

python

# 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)

python

# 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)

python

# 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

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

python

# 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:

python

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

❌ Insufficient separation time:

python

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:

python

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:

python

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

✅ Correct:

python

# 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:

python

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

✅ Correct:

python

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:

python

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

✅ Correct:

python

# 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

python

# 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

python

# 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