Certus Flex

The CERTUS FLEX is a contactless drop-on-demand dispenser built around Fritz Gyger’s own SMLD 300GC solenoid micro valves. Each channel is controlled independently, which is what makes it useful in a schedule: one instrument can lay down several different reagents at different volumes into the same plate in a single pass. Revolution drives it over SiLA, the interface the instrument itself publishes, and adds the two things a scheduled run needs on top of a dispense — gravimetric calibration correction applied to the requested volumes, and a record of what was actually commanded.

At a glance

Technology	Contactless drop-on-demand via SMLD 300GC solenoid micro valves
Channels	1–8 independently controlled, straight or 22° angled
Volume range	< 50 nl upwards, resolution > 0.05 nl
Accuracy	< ±3.0 % over 0.05–0.5 µl, improving to < ±1.5 % from 1.0 µl up
Precision	< 3.0 %CV over 0.05–0.1 µl, improving to < 1.0 %CV from 1.0 µl up
Labware	6, 12, 24, 48, 96, 384, 1536 and 3456-well plates; well plate heights 3–51 mm, or 18–75 mm for deep-well
Interface	Ethernet (1 Gbit/s, RJ45); SiLA
Revolution control	Dispense from a table, execute a stored method, prime, purge, air on/off, present the plate for load and unload

Specifications

Fritz Gyger publishes the figures above for the CERTUS FLEX, along with a 425 x 555 x 180 mm footprint, a 110–240 V 50/60 Hz supply and a pneumatic supply of 1.7–2.0 bar inlet pressure at a maximum of 5 l/min. Media listed as supported include buffer, cell media, cells, 100 % DMSO, proteins and beads.

Two consequences for scheduling are worth drawing out. First, the accuracy and precision bands tighten with volume — the sub-microlitre end of the range is where the instrument is least forgiving, and it is exactly where the driver’s gravimetric correction earns its place. Second, the well-plate height range decides whether a labware type can be dispensed into at all; deep-well plates are a separate, taller band, so a schedule mixing shallow and deep labware on one instrument needs both to be within the published height limits.

The manufacturer’s feature description gives the instrument as coming in two basic versions, of 5 or 8 individually controllable channels, while the specification sheet gives the channel count as 1–8. Take the channel count for a given unit from that unit’s own configuration rather than from the range.

Supported methods

The dispense itself is described by a table, and everything else is a SiLA command on the instrument.

• Dispense by table (XLS) — the main operation. xlsFile is an Excel dispense workbook that the driver converts to the instrument’s dispense-table XML; operationTimeout bounds the dispense; and applyGravimetricCalibration decides whether the requested volumes are first corrected using the system’s stored gravimetric calibration for this instrument. With correction on, the volumes commanded to the valves are not the volumes in your workbook — the workbook stays the statement of intent, and both the requested and the commanded table are recorded
• Execute method — run a method already stored on the instrument, by methodName, at a given priority
• Prime — fill the fluid path ahead of a run, for one liquid (the valve) and a volume
• Purge — the same shape, liquid and volume, used to clear a path. The driver also issues a purge automatically before a table dispense for any worksheet that specifies a non-zero pre-dispense volume, so priming behaviour can be expressed in the dispense table rather than as extra schedule steps
• Air — switch the air supply on or off
• Prepare for input and prepare for output — move to the given position so a robot can place or pick the plate. The driver runs prepare-for-output itself after an execute-method run, because the instrument leaves the plate under the valve head where a robot cannot reach it

Before a dispense, and before an execute-method run, the driver pushes the plate type of the labware currently on the device to the instrument. That happens just in time rather than at plate placement, so an instrument restarted mid-schedule still has the right plate type set.

Integration

The Certus is a SiLA device, and Revolution talks to it as one — over the instrument’s SiLA provider, with the schedule editor working from a built-in interface definition so operations can be laid into a schedule while the instrument is offline. The instrument takes a single device location; a device configured with more than one location is rejected on use.

With Record Dispenses enabled, every table dispense is written to the database as a pair: what the schedule asked for, and what the driver actually commanded after calibration correction. On a system under change control, that pairing is the audit record for the dispense — turning it off removes it.

Prerequisites

• The instrument’s SiLA provider must be reachable from the Revolution host, and its WSDL URL configured on the device.
• Methods referenced by execute method must already exist on the instrument.
• Dispense workbooks must exist as files the Revolution host can read.
• Gravimetric calibration data must be present in the system for an instrument if dispenses are run with correction enabled.

Device configuration

Property	Purpose
SiLA Provider WSDL URL	Where the instrument’s SiLA provider is served
SiLA Error Handling Timeout	How long the driver waits on the instrument’s SiLA error handling before giving up
Use SiLA Simulation Mode	Runs against the instrument’s own simulation rather than its hardware
Event Callback Host	Host the instrument sends SiLA event callbacks to — needed on a machine with more than one network interface
Number of Valves	Valve count for this unit. Defaults to 5
Record Dispenses	Whether requested and commanded dispense tables are recorded to the database. Defaults to on
Simulation Model File Path	Mesh used for the instrument in the 3D system model

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