Particulate contamination can block the orifice of the MicroJet dispensing device and interfere with operation. Thus, having a clean operating environment is essential.
- Avoid handling dispensing fluids, tubing, and dispensing devices in areas susceptible to dust or static electricity that attracts dust. Static charges are more prevalent in conditions of low relative humidity (Store the dispensing devices, tubing, fluid containers, and swabs in an enclosed dust free area when not in use.
- Filter air incoming from the pneumatics control system and all fluids that will enter the device using a 5 micron or smaller pore size filter.
- Be certain that all fluid handling materials (i.e., glassware, tubing, filters, etc) have been thoroughly cleaned and/or rinsed with filtered water or an appropriate solvent.
- Use appropriate lab apparel (lab coat, glove) to reduce contamination from your clothing or skin.
The orifice of a MicroJet device is subject to clogging and blockage by particulate material present in the jetting solution. The filtration of the jetting solution prior to use is essential. Before dispensing you should:
- Flush new syringe filters prior to use to remove particles from manufacturing.
- Confirm the tubing and reservoir will withstand the solvents you choose. Otherwise dissolved material can contaminate the dispensing device.
- Flush the tubing and reservoir with a filtered solvent before dispensing, and then dry with filtered pressurized air. Filtered isopropyl alcohol (or other solvent) has a greater wetting capacity than water and is a better choice for removing particulates.
- Always clean the dispensing device before use. Back-flush the device by applying vacuum through the fluid connector and immersing the glass tip within a clean solvent. This back-flush method can also be used to remove orifice clogs. Warm solvents under low power ultrasonication work best, but understand the dangers of heating and sonicating volatile solvents. Do not to sonicate for more than 1 minute and never immerse more than the glass tip into the cleaning solution.
MicroJet devices must be cleaned immediately after use to ensure reliable dispensing and extended operational life. Note: The inline filter must be removed from the MJ-AL style devices prior to cleaning.
- Use a wet clean foam swab or tissue wetted with water or solvent, to clean the exterior surface of the dispensing device, including the metal body and glass tip. Inspect under a low power microscope to confirm the glass tip surface is clean.
- The filter of the MJ-AL style devices must first be unscrewed and removed. The device is then reattached to the female luer fitting (see image to the right), prior to performing the cleaning or clogged orifice recovery procedures outlined below. The inline filter section should be soaked in suitable cleaning fluid. The filter should then be attached to the female luer fitting and purged with cleaning fluid from the luer fitting side to remove contaminates. Use only hand tightening to attach the female luer fitting, the inline filter and the device body during reassembly to avoid over tightening and damage.
- Back-flush the device with 1-3mL of the solvent of the solution that was dispensed followed by a 2% water solution (80ºC) of Micro-90 cleaning solution (Cole-Parmer cat # U-18100-00) or equivalent. Inspect the glass tip of the dispensing device using a low power microscope/stereoscope. Observe the tip of the dispensing device after 1 minute of back-flushing to verify all residues, particles or condensations have been removed. Repeat the procedure until the tip is clear. Lastly, back-flush the tip using DI or MilliQ water for at least one minute, followed by a one-minute back-flush using acetone. Apply vacuum for one-minute to dry the inside of the device and then dry the cleaned device in an oven at 70ºC for 30 minutes prior to storage or use.
- Difficult materials, such as proteins, DNA, antibodies, etc., can be removed with a 10% sodium hypochlorite solution before cleaning with 2% water solution (80ºC) of Micro-90 cleaning solution. Rinse and dry the device as described above.
- Stubborn particles can be often removed after soaking only the orifice in the cleaning solution for a few minutes to overnight prior to back-flushing.
Clogged Orifice Procedure
An orifice blockage that cannot be removed using the cleaning and back-flushing procedures described above may be removed using the following protocols. Please note that leaving solutions in the device for extended periods of time, such as overnight, can result in orifice clogging.
- Immerse the tip of the device and backflush with a 2% solution (80°C) of Micro-90 Cleaning Solution (Cole-Parmer cat. # U-18100-00) in a beaker held in an Ultrasonic cleaner. Avoid the use of high power output Ultrasonic cleaners, as they can damage the fragile orifice. Also, minimize the amount of time the MicroJet device tip is exposed to Ultrasonic cleaning. Check the condition of the orifice after one minute. Repeat if necessary. A cotton swab can be used to wipe the tip of the device during this procedure to help free the clog.
- If the orifice remains clogged, immerse the tip of the device in a 5% water solution (80°C) of Micro-90 Cleaning Solution (Cole-Parmer cat. # U-18100-00) for overnight. Then, perform the backflush procedure described in “1” above.
- The MJ device can be returned to MicroFab if the cleaning procedures described above fail to unclog the orifice. The device will be cleaned, retested, and returned with a service fee applied. For each returned device fill out and attach the Dispensing Device Return Form (found under Support/Return Forms). Note: A completed form is required for each device returned. Do not combine multiple devices onto one Dispensing Device Return Form.
Do not immerse the body of the MicroJet device into the Micro-90 Cleaning Solution or other solvent, as these fluids can damage the epoxy and nickel coating of the PZT. Water and/or IPA can be used to clean the MicroJet casing.
Avoid the use of high power output ultrasonic cleaners, as they can damage the edge of orifice. Also, minimize the amount of time the MicroJet device tip is exposed to ultrasonic cleaning.