Proper probe preparation is essential for successful FluidFM experiments. This guide covers three stages: preparing the probe solution, filling the reservoir, and loading the probe into the system. Each stage affects experimental outcomes and helps prevent common issues like probe blockages.
Probe solution considerations
The probe solution is the working fluid dispensed through the FluidFM probe during experiments. This solution can be aqueous, oil-based, or specialised media depending on your application requirements. Proper preparation of the probe solution is critical for successful experiments, as it directly affects flow characteristics, probe longevity, and experimental outcomes. This section outlines essential preparation steps and considerations to ensure optimal performance and prevent common issues such as probe blockage.
Figure 1. FluidFM probe filled with Lucifer Yellow. The multiple images show an increase of pressure from 0 mbar to 10000 mbar.
Chemical Resistance of FluidFM Probes
For the FluidFM OMNIUM, the plastic consumable is made of Makrolon (polycarbonate). Brief exposure (seconds) is generally safe for most compounds, while prolonged exposure may cause degradation:
Table 1. Summary of components for which our FluidFM probes are not resistant.
Our technical experts employ precision gluing techniques to ensure proper alignment between the microfluidic channel in the chip and the sample reservoir in the adapter. There are two adhesive systems available, depending on the probe type: an acrylic-based adhesive (Loctite® AA 3311) for MAT probes and a medical-grade epoxy adhesive (Panacol Vitralit® 1605) for BIO probes. Both adhesives are cured using UV radiation to achieve optimal bonding strength.
According to manufacturer's technical specifications, Vitralit® 1605 demonstrates excellent chemical resistance across a broad range of substances. However, prolonged exposure (>24 hours) to aggressive solvents such as ethanol or acetone may result in adhesive degradation (separation of the glued layers).
Loctite® AA 3311 exhibits good chemical resistance, with documented compatibility for water immersion (including boiling water), isopropanol exposure, and elevated temperature/humidity environments.
It should be noted that the plastic consumable (Makrolon) typically exhibits lower chemical resistance. Therefore, the chemical compatibility limitations of the FluidFM probe plastics, rather than the adhesives, generally determine the overall chemical resistance of the assembled probes.
Optional: Add a fluorescent tracer to the probe solution:
- Provides enhanced visibility of solution flow during experiments.
- Helps identify probe blockages and leaks.
Remove particulates from your probe solution before use to prevent clogging. Choose one method to remove particulates:
- Filter: Use a 0.22 µm filter (e.g., Costar Spin-X, Cat. #8160).
- Centrifuge: Spin down solution for 20 min, 16,000 x g (rcf), 4°C.
Probe Reservoir Filling
After preparing your solution, fill the probe reservoir. This component stores your working solution and connects to the probe via microchannel. Proper filling prevents air bubbles and pressure fluctuations during experiments. Follow these steps to ensure reliable fluid supply throughout your experimental session.
- Aspirate 1 μL of probe solution with a pipette tip.
- Warning: Volumes exceeding 1 µL can damage the FluidFM head over time.
- Stabilize your hands by placing both elbows on the table.
- Insert the pipette tip at a 45° angle.
- Lower pipette to the bottom of the reservoir.
- Release liquid.
- Flick the probe head gently to move fluid down into the bottom of the reservoir.
Figure 2. Lateral view of the filling of the reservoir.
Considerations:
- Air bubbles can block the probe.
- Remove by pipetting them out.
- Avoid spillage outside the reservoir.
- Liquid outside the reservoir can damage the FluidFM head.
- Aspirate any misplaced liquid with the pipette.
- Avoid touching the pipette tip to the side of the reservoir
- Stray liquid can cause laser scattering
- Clean any spills with a cotton swab or Kimwipe
- Verify cleanliness by visual inspection or stereomicroscope
- Touching the tip off the side of the consumable
- Stray liquid can cause the laser the scatter
- Clean stray liquid with a cotton swab or a Kim-wipe
- Verify cleanliness through visual inspection or stereomicroscope examination.
Figure 3. Correct (a) and incorrect (b, c) probe reservoir filling" with proper integration into text.
Loading the probe in the system
The probe loading procedure completes the preparation sequence, physically installing the FluidFM probe into the instrument. During this step, you'll mount the probe assembly, establish fluidic connections between the reservoir and probe, and verify secure positioning. Correct loading technique protects the fragile probe components while ensuring the system is ready for the automated calibration procedures in the Preparation Advance Workflow.
- First, place the probe plate in the FluidFM Omnium system. In the ARYA software, you can exchange or add plates using either:
- Exchange Plates in Preparation Workflows – Select this option from the right menu.
- System
Initialization – Appears automatically when opening a project
- Figure 4. System initialization window, showing the plate selection
- Select the desired port - Click ‘To Right Port’.
- Select the ‘ProbePlate’ from the drop-down menu.
- Ensure that the probe loading plate is then placed correctly in the right port:
- The letters on the plate should be readable from the port door (right-side up).
- Magnets are aligned correctly in the slots.
- Press down on all four corners of the plate. The plate is pushed down as
far as it can go.
- Figure 5. How to place the probe loading plate into the FluidFM OMNIUM stages.
- The probe plate can also be placed on top of a wash plate. Verify it is completely pushed down on to the plate before placing into the system.
- Note: Use Nunc 12-well plates only.
- Place the probe in the probe loading plate:
- Place the probe in one of the raised slots only (A1, A3, C1 or C3).
- Ensure the probe is in contact with the surface of the holder on insertion.
- If not, twist the probe 180° and reinsert.
- Remember the probe position for reference during setup
Figure 6. How to insert the FluidFM probe into the probe loading plate.