Like Having Another Person in the Lab
Your liquid handler is a marvel of modern engineering. These helpful systems can relieve lab employees of most sample processing tasks. Benefits include increased productivity, fewer errors, reduced injuries, and less boredom. This all leads to lower turnover for lab personnel and reduced costs for the lab. These improvements can be so significant that these robots become the focus of the lab. The love is so strong that many labs even give their liquid handlers names and personalities! (At one company, liquid handling systems were named after the divas – Whitney, Celine, Christina, and Brittney! At another, names were Lord of the Rings themed.)
We appreciate these machines for the work and support they offer our laboratories. But, made of metal and plastic, it’s easy to forget they need proper care, much like their human counterparts. We see the same story time after time:
- a new robot enters the lab
- production ramps up due to the increased capacity
- weeks turn into months and everyone is happy
- then … the liquid handler performance drops
What can you do to set up your system for success?
Loss of pipetting performance (lower accuracy and precision) is bad enough. But in extreme cases, performance issues can completely shut down a lab. You can avoid this terrible situation. Nobody wants to be “down.” Regular preventative care (by you) and annual service (by the pros) will keep your robot in great shape. Proper care and feeding boil down to a few common-sense tactics:
- Establish a maintenance plan (and follow it)
- Keep your system clean (inside and out)
- Make sure your connections are air-tight
- Use the correct / high-quality materials – liquids / reagents, consumables, and parts
- Have an annual preventative maintenance service
Care of the liquid system – the heart of the liquid handler
Some very advanced technology goes into modern lab automation systems, including:
- Precision motion control
- Air and liquid-based dispensing
- Liquid level sensing
- Sample tracking
- Safety features
- Device integration and communications
Although, a simple view of a liquid handler is: pumps, moved by motors, connected by tubing to pipette tips. Each of these basic elements has their own potential for failure. Knowledge of how they function will help us prevent problems and keep the system running. Most liquid handling systems have at least two sets of pumps: a fast pump and syringes.
The large volume, fast wash pump
The fast pump also called a wash pump, is for moving large amounts of liquid. The fast pump can be a piston pump, diaphragm pump, or peristaltic pump. The fast/wash pump generally supplies water for washing the system out. These pumps can also supply buffer or other liquids for filling large volumes. This happens with lower precision than syringe pumps, but much faster.
To pass the original manufacturer’s testing, the fast pump must be able to meet a specific flow rate. This is a large volume in a set amount of time; 1600 µL per second for example. In most cases, there is a large margin of safety in this specification. A good pump and tubing should have no problem moving 150% of this required rate. If the source lines become clogged, worn, or leaky, the flow rate can plummet. You can flush the tubing lines with distilled water, and even replace the tubing if it becomes too fouled. You may be able to clean the tubing with a cleaning agent. The manufacturer may have recommendations for solutions and procedures to use for cleaning. But, if the pump is the source of the problem, then replacing the entire pump assembly is more cost effective than repairing it.
The precision pipetting system – syringes
The syringe pumps are for delivering more precise volumes. Syringes are smaller piston pumps that can dispense volumes from <1 µL to 10 mL or so. These pumps are best utilized in steps requiring smaller or more controlled volumes. Also, syringes can aspirate liquid from one container and dispense into another, while fast pumps are usually one-way – only dispensing liquids. The accuracy and precision requirements for syringes depends on their capacity. A smaller syringe, say 500 µL, will have a stricter accuracy and precision specification than a larger syringe, like 10 mL. The manufacturer will factory test the syringes using either colorimetric or gravimetric methods. As with the fast pump unit, it’s most effective to replace the entire syringe if one becomes faulty.
The best maintenance task for fast pumps and syringes is a distilled water system flush. Liberal flushing of the system will rinse away corrosive liquids and solid particles. There is no danger in doing this often. It’s recommended to perform a flush each time the system has completed handling biological fluids or reagents. Also, if the system has been sitting unused for a while, a system flush will help to keep it from deteriorating.
Consistency is key with all maintenance procedures. Many labs create log books to document these steps with signatures, times, and dates. Most active labs will keep the liquid handling robots busy, and regular use is good for these systems. But, intermittent robot users should be extra vigilant about keeping the system clean with regular flushes.
Leaks and Clogs
Obstructions and leaks are the #1 problem to avoid on pipetting systems. Leaks can be problematic because they may not be visible on liquid handlers. We tend to think of leaks as dripping liquid OUT of the system. This can and does happen, but you may be more likely to encounter leaks that let air INTO the system. Leaks and clogs affect the pipetting pressures, which kills accuracy and precision. Manufacturers design their systems to resist leaks and clogs, but they are common.
Leaks – running an (air-)tight ship
While very rare in a properly assembled liquid handler, leaks can happen and are most common at the connections. The pressure inside a system’s tubing changes during operation. This expansion and contraction can loosen connections over time. You should be especially concerned about the “finger-tight” connections between diluters and valves. These can loosen over time. While a puddle is the most obvious sign, visible bubbles in any of the system’s lines is also a good sign that there is a leak. Even tiny leaks can have a large effect on the accuracy and precision of the liquid handler. The pipetting action depends on the liquid column to provide a capillary force. Trace the flow of liquid from the source and look for where the bubbles originate. Then ensure all connections from there are tight. This should fix the problem. But the tubing will need replacement if leaks continue to appear.
Clogs – keeping the openings clear
The likeliest place for a clog to occur is in the smallest openings: a diluter, a syringe, or pipette tip itself. Diluters are valves that switch liquid flow between the pump and the syringes. Regular flushes are your go-to maintenance tactic. But, the next best way to keep these openings clear is to use only approved materials for your system. This includes reagents, systems liquids, consumables, and parts. Using incorrect or low-quality materials can cause buildup in or degradation of the system’s liquid path.
For example, most of the tubing on the liquid handler is durable PVC. This is an excellent tubing material for most applications. But it’s incompatible with certain reagents. For example, using a system liquid like DMSO will quickly degrade the tubing and cause leaks. Planning with a trained application engineer can help reduce the risk of this. In some cases, you can use an alternate tubing material like PEEK, that is resistant to the solvent. In other cases, you can try to avoid contact of the materials with the incompatible parts of the system.
The end of the line – leaks or clogs at the tips
Leaks or clogs will occur with both fixed and disposable tip systems. Fixed, washable tips are often for procedures that call for low volume transfers. Since these tips are thin metal tubes, they can become bent (obstructed) or cracked (leak) if damaged in a crash. Proper software scripting and consideration during protocol development can reduce this risk.
Disposable tips are less likely to clog, but leaks can form if the tips are not seated well on the tip adapter. Improper setup of the system or the use of low-quality tips can cause this leak. Both conditions are preventable. Professional service during installation or maintenance can solve the setup problem. And careful selection and validation of tip vendors will avoid the seating issue.
One other source of leaks is where the fixed tip or disposable tip adapter inserts into the tubing. Both fixed and disposable pipette tips depend on this connection to be air-tight. This is not a common point of failure, but the improper initial setup of the system can cause leakage over time.
The hard(ware) part of the system – easy to maintain
We’ve spent most of the time discussing how to avoid or solve problems with the pipetting part of the system. With good reason, this is the critical part that affects results most. We can’t ignore the rest of the system, though. In general, the liquid handling part of the system is the most error-prone. But, the rest of the system hardware requires some TLC as well to keep it in tip-top shape. Movement is an important part of the system. Most liquid handling robots have arms controlled by motors mounted on wheels/bearings. This arm usually runs along a track or rail covered in lubricating grease. This grease can gather dust and debris which will cause performance issues. If the wheels/bearings become fouled, they could bind or skip and cause motor errors or inaccurate movements. You can care for this yourself, as follows:
- wipe away the contaminated residue with an alcohol solution
- replace the lubricant with a small amount of clean (manufacturer qualified) grease
The Annual Preventive Maintenance Service
Yearly maintenance by a trained service engineer is important for a healthy liquid handler. A typical annual preventative maintenance (PM) service will include at least the following:
- replacement of all the system liquid tubing for syringes and fast wash pumps
- inspection/replacement of worn syringes and diluter valves
- inspection/replacement of worn pipettes tips and tip adapters
- inspection/cleaning/lubrication of moving parts
- calibration of movement
PM visits are available as pay-as-you-go services or can be parts of a yearly service contract. Annual service contracts usually also include emergency service coverage. You’ll need to determine the best approach for your lab based on your usage of your lab automation system. If it’s a critical part of keeping your lab running, then you may want to consider a service contract. The cost of lost productivity from downtime can far outweigh the price of a service contract.
Atlantic Lab Equipment is ready to help you find a system that is best suited for your lab’s needs. We can also provide ongoing support for your newest team member! With proper installation and annual maintenance by a service professional, and weekly and monthly maintenance by your lab staff, a liquid handling robot will provide a very real return on investment for many years.