Thermo MultiDrop

The Thermo Scientific Multidrop Combi family are cassette-based bulk reagent dispensers: a peristaltic pump pushes reagent through a swappable dispensing cassette into every well of a plate. There are two quite different instruments behind the name, and Revolution has a separate device for each — the microlitre-range Combi and the nanolitre-range Combi nL.

The dispensing protocol lives on the instrument, or is transferred to it from Thermo’s FILLit PC software. Revolution’s job is to name the protocol and the plate, and to run it at the right point in a schedule.

Thermo’s current line is the Multidrop Combi+, the Multidrop Combi SMART+ and the Multidrop Combi nL. The earlier generation is gone: of catalogue number 5840320, Thermo states plainly that “The product (5840320: Multidrop™ Combi Reagent Dispenser, Multidrop Combi with SMART 2 option) has been discontinued.” Revolution’s device is named for the older Combi, and installed units are still driven — the serial command interface is unchanged in principle — but a new instrument will be a Combi+ or a Combi SMART+.

At a glance

Current models	Multidrop Combi+, Multidrop Combi SMART+, Multidrop Combi nL
Dispensing technology	Peristaltic pump, 8 channels
Volume range	0.5 µL – 2500 µL (Combi+ / SMART+); 50 nL – 50 µL (Combi nL)
Plate formats	6-well to 1536-well (Combi+ / SMART+); 96-, 384- and 1536-well (Combi nL)
Interface	On-board software, and serial RS-232 or USB for PC control
Revolution control	Run a dispensing protocol, prime the hoses, shake; pressure on/off on the nL

Specifications

Multidrop Combi+ and Multidrop Combi SMART+

Dispensing volumes	Small tube cassette 0.5–50 µL in 0.5 µL increments; standard tube cassette 5–2500 µL in 5 µL increments
Dispensing accuracy	Small tube cassette 2 µL ±10%, 10 µL ±5%; standard tube cassette 20 µL ±2%, 100 µL ±1%
Dispensing precision	Small tube cassette 2 µL CV ≤5%, 10 µL CV ≤3%; standard tube cassette 20 µL CV ≤1.5%, 100 µL CV ≤1%
Dispensing speed	96-well: 10 µL in 5 s, 20 µL in 5 s, 100 µL in 10 s. 384-well: 1 µL in 6 s, 5 µL in 9 s, 10 µL in 13 s, 20 µL in 21 s. 1536-well: 1 µL in 15 s, 5 µL in 28 s
Plate heights	5–50 mm
Dead volume	<1 mL for the small tube cassette; <7 mL for the standard tube cassette. Reagent can be backflushed into the original reservoir
Dimensions (W × H × D)	35.6 × 21.8 × 32.8 cm (14.0 × 8.6 × 12.9 in)
Weight	9.1 kg (20.1 lb)
Electrical requirements	100–240 V, 50/60 Hz

The dispensing speed figures are the ones to plan a schedule around. A 20 µL fill of a 384-well plate is a 21-second occupancy; the same volume into a 96-well plate is five seconds. If the dispenser is a bottleneck in a cell, the plate format is usually why.

Dead volume is a scheduling concern too, not just a cost one. Priming and the volume held in the cassette have to be accounted for in the reagent you put out at the start of a run, or a long unattended run finishes dry.

The SMART+ differs from the Combi+ in traceability rather than performance: its RFID-enabled SMART+ dispensing cassettes are tracked automatically for usage. That tracking is on the instrument, not in Revolution.

Multidrop Combi nL

Dispensing increments	1 nL over 50–999 nL; 10 nL over 1.00–9.99 µL; 100 nL over 10.0–50.0 µL
Accuracy	<1 µL ±5%; >1 µL ±2%
Precision	CV ≤10% at 50 nL, to CV ≤2% above 10 µL
Dispensing speed	50 nL in 6 s and 1 µL in 8 s, into a 384-well plate
Dead volume	<1.2 mL
Dimensions (W × H × D)	35.5 × 22 × 37.5 cm
Weight	9.6 kg

Supported methods

The dispensing itself is defined by the protocol held on the instrument. Two Revolution devices cover the two instruments, and their operations differ — the nL identifies its plate by name, where the Combi identifies it by numeric plate type.

Multidrop Combi

• Dispense — run a named on-board protocol, given a plate type ID (numeric), a protocol name and a timeout
• Dispense with default parameters — the same call using the device’s three configured defaults, so a schedule step carries no parameters at all
• Prime dispense hoses — prime with a given volume, under a timeout
• Shake — shake for a shake time, at a shake distance and a frequency in Hz

Multidrop Combi nL

• Dispense — run a protocol by protocol name for a named plate name, under a timeout
• Prime dispense hoses — prime with a given volume, under a timeout
• Pressure on / Pressure off — bring the nL’s dispensing pressure up and down, each under a timeout
• Shake — shake for a shake time, at a shake distance and a frequency in Hz

Prime dispense hoses is not optional housekeeping in a schedule: a cassette that has been changed, or has stood since the last run, dispenses short on the first plate. Put the prime in the schedule rather than relying on someone remembering it at the instrument.

On the nL, pressure on and pressure off are separate operations because pressure is a state the instrument holds between dispenses. Leaving it on across a run avoids paying for pressurisation on every plate; a schedule that ends without turning it off leaves the instrument pressurised.

Integration

Revolution talks to both instruments over serial, using the Multidrop command protocol. Plate movement in and out is handled by the driver rather than by the schedule: before a mover picks from or places onto the device, the driver moves the plate carrier to its out position, so no explicit plate-out step is needed in the schedule.

When the device is uninitialised, the driver sends the instrument’s quit-remote-control command. That matters practically — until it is sent, the instrument’s own touchscreen panel stays locked out.

Prerequisites

• The dispensing protocols the schedule will call must already exist on the instrument, created on the front panel or transferred with FILLit.
• The instrument must be cabled to the Revolution host and its serial port known before the device is initialised.
• Cassettes and tubing must be fitted for the volume range the protocol expects, and primed.

Device configuration

Property	Purpose
COM Port Settings	Serial line settings for the port the instrument is on
Default Dispense Plate Type	Plate type ID used by dispense with default parameters
Default Dispense Protocol Name	Protocol name used by dispense with default parameters
Default Dispense Operation Timeout	Timeout used by dispense with default parameters

The three defaults exist so that a cell which always runs the same fill can call a parameterless step. Where a schedule dispenses more than one reagent or more than one plate format, set them per call on dispense instead and treat the defaults as a fallback — a stale default protocol name is a silent way to dispense the wrong volume.

The Combi nL device has no properties of its own beyond its serial settings; its plate and protocol are named on each call.

If you need more of this instrument driven from a schedule, get in touch — the driver is extended on demand.