After some great comments some of you gave me about the hamilton vs tecan (thanks to everyone who took the time to comment), I would like to ask about the difference between a liquid and air system for the 8-channel Tecan arm on an EVO.
I know the benefits of the system but I did talk to someone who used them extensively (had 10+ of them during COVID) and he mentioned “tightening valves sometimes” or something along these lines.
Anyone can comment on the daily maintenance of the liquid system compared to air one?
please see the EVO Operating Manual 392886_en_V10_1.book for details on daily maintenance. The liquid LiHa arm requires more work, particularly refilling of system liquid container and emptying waste container.
Here the relevant table, note the sections ‘liquid system’ and ‘system liquid container’ that do not apply for AirLiHa systems.
While I have never used a Evo liquid system, I have worked with a Biomek system before which is also liquid based. Besides the extra maintenance, there are some other things to keep in mind too when using a liquid system.
A good example is needing to pay very close attention to your liquid classes when doing vigorous mixing. With liquid base systems, you have a higher chance of collapsing your air gaps between your system liquid and your pipetting liquid. I have a method where I need to purge the water after certain mixing steps to rectify this.
I agree with @evwolfson , only get liquid if you have a very very specific benefit that liquid would give you that air does not.
I will add that in my experience the liquid systems are significantly more robust. If you want a system that will work day-in/day-out for 10 years the liquid systems are what you want. If you want an easy to use walk-up system that can be used by 20 different people the AirLIHAs probably fit better.
The AirLIHAs need parts replaced more frequently but the day to day maintenance is basically nothing. The liquid LIHAs like regularly scheduled PMs to replace valves/tubing, but I’ve used older systems that didn’t get any attention at all and they still worked flawlessly.
The liquid LIHAs obviously need system liquid and a liquid waste container. And they need some thumbscrews checked and tightened once a week. From a hardware perspective that’s about it.
@UCantBcereus brings up valid points about liquid classes.
Thank you all for the comments, appreciate it.
I intend on using the system mostly for ELISA which doesn’t require working with viscous liquids. That’s my main gripe with the liquid system - it’s just more work for not much benefit. The only plus (aside for being more robust over the years and cheaper to fix) is the ability to use fixed tips. But that I can also do with a Hamilton STAR if I want to (currently checking both robots as an option)
@UCantBcereus when you say vigorous mixing, you mean at high flow rates? @jnecr easy to use in your perspective is that more often than not you don’t need FSE or someone that knows the system enough to tighten screws and such?
These are the screws, there’s a couple of thumb screws at the top where the tubes attach and at the bottom holding the syringe plunger. There’s also a few up in a top compartment that are good to hand tighten periodically to prevent air leaks. This picture is from a biomek but it’s the same stuff as you’d see on an Evo aside from the tube size (depending on syringe volume).
With a liquid LIHA you need someone who is responsible for regularly checking a few things on the instrument. Mostly just that it doesn’t run out of system liquid, it doesn’t fill up its system liquid waste container, the system liquid is getting properly flushed at the beginning of the day/run. And every few days to weeks you need to check that the syringe thumbscrews are tight and air is not leaking in through those connections.
It is immediately obvious when you have air intrusion when you know what you’re looking for. But if you intend to have scientists use this instrument as a walk-up for their ELISA they won’t know what to look for and their ELISA could be ruined if the instrument isn’t properly flushed and/or the thumbscrews aren’t tight.
You’ll have fewer FSE visits with a liquid LIHA. Those AirLIHA systems have a way of needing to get replaced every few years depending on how much use they get. I believe if you’re under a service contract they generally get covered. If you aren’t you’re looking at $$$ to get them replaced.
Is there a source for this? Liquid LiHA’s have overall more parts to maintain which means that there is a higher likelihood for a service intervention. Furthermore since they’re in constant contact with a liquid, components should be swapped quite regularly. There are also other things like lines getting kinked, tubings get annoying air gaps and leakage is a real hazard. You also need to have a robust liquid detergent, ethanol and flushing maintenance cycle. For the aforementioned, at least once a week if you’re a heavy use lab or if it’s been idle for 2+ hours you should do a super thorough flush. The first AirLiHA’s had some problems but they overall have less parts to maintain and it’s easier to swap an arm or a channel in the field because you do not have a lot of tubing. The motors also generally have better precision. Swapping an arm or a channel is a pain but swapping the other parts, way less effort.
The benefit of a service contract is that you get parts swapped before you even get to think about them breaking down so we would often have syringes, o-rings, needles swapped at every PM (sem-annual, quarterly interval) and then every annual PM the tubing was swapped as preventative measure.
For newer components ( I am including the airLiHA), I don’t think that any liquid handling company is saying that they’re indefinitely good. Most companies state that every 3 years or so (in high throughput labs), you should basically re-do an IQ/OQ and have hardware swapped.
I agree that if you aren’t on a service contract, it’s $$$ to get anything replaced in this industry.
Liquid LiHA’s have overall more parts to maintain which means that there is a higher likelihood for a service intervention.
When you consider the parts inside the AirLIHA, I think you’ll see that Liquid LIHAs have fewer parts and they are much more robust.
Furthermore since they’re in constant contact with a liquid, components should be swapped quite regularly.
Not true if using water as the system liquid, which 90% of systems use. The other option is DMSO as a system liquid which they have components specifically for DMSO system liquid systems and they are all DMSO resistant. PMs generally have the tubing replaced once per year, but for water system liquid instruments I find this to be overkill. At and old lab that I worked in we decided to stop PMing a super old Tecan (Genesis RSP) that ran water as a system liquid and it never missed a beat for 5+ years. Water just isn’t corrosive to plastic.
You also need to have a robust liquid detergent, ethanol and flushing maintenance cycle. For the aforementioned, at least once a week
I actually recommend the opposite. If you’ve regularly flushing your system with detergents or something like ethanol this is probably where your problems started. Especially if you’ve been told weekly. If you use proper, clean, DI water and the system gets plenty of use I would never use a detergent on the liquid system. You’re only asking for problems. I’ve never had any growth in a system that gets regular use (actually, I’ve never seen growth on a system that uses clean, DI water, but I’m sure it happens).
Flushing with system liquid prior to use is absolutely necessary, and part of my point with having dedicated personnel use it and know what they need to do. This is the biggest issue I’ve seen with walk up systems. Scientists don’t know that they need to flush the system to remove air bubbles prior to using it. They just want to use the system. So having someone dedicated that knows what they’re doing is preferred, either that or part of the protocol that gets run does a very thorough flush to remove air bubbles which will be wasteful most of the time.
10+ years, 100+ Tecan’s (seriously!). Still doesn’t count as a source.
I misspoke, it was detergents once a month and yes there are reasons why we had to implement these rules. Ethanol flush was once a week, again for reasons.
PMs generally have the tubing replaced once per year, but for water system liquid instruments I find this to be overkill. At and old lab that I worked in we decided to stop PMing a super old Tecan (Genesis RSP) that ran water as a system liquid and it never missed a beat for 5+ years.
That tubing stretches, it’s malleable. Don’t disagree but in a 24/7 lab, the annual swap coincided with right around when we started to see issues. Our workflows weren’t your workflows so it’s not a 1:1 comparison. The o-ring tightening also caused problems with Liquid LiHA’s.
I’ve never had any growth in a system that gets regular use
You’re lucky.
protocol that gets run does a very thorough flush to remove air bubbles
@Optimize was able to implement a workflow that looked at idle time and performed an extra thorough flush prior to use. It was great but yeah we had to train scientists on this and make it part of the daily and post-run checks.
I would say Liquid is, despite the additional maintenance needs, a more robust mechanism if you are doing certain applications
for low volumes, free dispense etc - nothing beats the resolution & control of the Air LiHA/FCA
but volumes over 10-20uL, up into the range of 1mL+ - a syringe based system can be just as good,
for ELISA, i have always preferred fixed tips as the washing of tips & larger tip capacity for reagent addition etc (1 mL disposable tips, 12 x dispenses of 100 uL is handled as 600 uL for 6 x 100 twice) …
happy to chat specifics,
re Air LiHA “maintenance”, nothing is maintenance free - and I believe Tecan swaps out the mechanics every year or 2 to avoid problems - this comes at a significant cost,
for liquid system maintenance, a well-documented maintenance routine/script with actual trained users can be effective for 5-10 minutes a day, and an extra 30-60 mins every week - plus with camera integration etc & AI, issues can be seen, recorded & problems identified before they become an issue
Yeah it was nice to implement a solution as part of the Daily QC by leveraging Introspect to predict wear & tear before it’s in production. Saved me a ton of tickets.
In that case this whole forum is useless. You’re asking for a source on something that is unsourceable. Tecan probably has the data but everything on this forum is anecdotal.
That tubing stretches, it’s malleable.
It’s not a peristaltic pump (except at the FaWa). 1) why is your tubing stretching? 2) Who cares? That’s not what controls volume anyway. I’ve never had a problem with tubing stretching. Actually, I’ve never had a problem with tubing at all, even rubbing, even on a DMSO system. We would just have it replaced because that’s what Tecan does during a PM. We’d wear out plenty of other components, but tubing was never one of them.
Over time the belt on the diluters would stretch a touch on Genesis instruments and if you asp/disp really quickly you could skip a tooth on the gear and your volumes would be off accordingly. Tecan fixed that with screw drives on the Evo diluters (actually I think early Evos still used belts, but I could be wrong).
Overall, I still stand by my statements. If you want a workhorse that’ll go for years with minimal problems I’d go with a liquid LiHa. If you want a more fool proof walk up instrument that gets occasional use, go for an AirLiHa. There are definitely applications that should push you in one way or another, but leaving those alone I prefer liquid LiHas.
Also, as an example of robustness, I would never purchase a used AirLiHa instrument, the likelihood that you’re going back to Tecan to replace the AirLiHa on your dime is too high. For liquid LiHas I’d purchase it sight unseen as long as I knew I’m also getting the software dongle (in the case of Evo instruments).
My use is definitely under the “fool proof way walk up instrument that gets occasional use”, so that does make sense for my preference for the air system. We did have it under as service contract too, so that’s a great point to consider as well and might sway one way versus the other.
The target audience relationship to automation can play a factor here too. If you tell a lab that’s hesitant about automation that they have do easy but regular maintenance, then that may enhance negative attitudes about using the device (it’s really easy to add an air LiHa check before every method so the user doesn’t even need to think about it). If you’re in a lab where you have people that you’re confident will do maintenance and not have a problem doing so, then its less of a concern.
On my Biomek I have a situation where I’m mixing a large volume (35 ul into 875 uL) in 1000 uL tips. I Mix 10 times with an aspiration rate of 100 uL/seconds and dispense at 250 uL/sec. After this mix, I need to run a “wash Tips” Step to reestablish the system trailing air gap. Otherwise I’ll see an issue where system liquid will leak into my disposable tips.So the speeds are not what I’d call crazy, but this is something you would need to be ready to recognize and adjust in a liquid system.
Its more of a diagnostic tool than anything. It’s a command you can drop into the beginning of your script, it will check the air resistance through some inline air filters that are part of the air channels. Those can be fairly easily replaced on as as needs basis by a user if they fail. Anything more than that is probably an expensive Tecan visit if you don’t have a service contract.
I was taught by Tecan that you want to “warm them up” by running this air resistance check 10X at the start of a day, but I don’t have any evidence of knowledge of why that helps. Rather than have a user need to remember to do this, I just put this 10X check at the start of a method so that any issue can be seen at the start of a run before it starts running with actual samples/reagents etc.
Great discussios here. A point we’ve missed though, is what’s the scientific application? Are you running experiments that are low in volumes like PCR’s, also the throughput, air displacement means you need space for tip racks. Another point is if you want to run protein purification with robocolumns then it will only work with fixed steep tips with liquid displacement.
Accuracy and precision can always be tweaked with the liquid class settings so I don’t think there is a huge variablity between liquid and air. But as mentioned above liquid displacement does have the added burden of running flushes and ensuring the tubing is clean and nothings growing.
