[DIYbio] Re: DIY Labware review

Here's a thread with a few made from drills or dremel type drives...

http://www.sciencemadness.org/talk/viewthread.php?tid=949&page=23

Another thing I see is the laminar flow hood section.  My advice on that is that laminar flow does not work well for micro.  People use them plenty, but I don't feel like blowing your work directly into your face is really a very good practice.  

Biosafety cabs. are too complicated to DIY IMHO.  I don't think you could really get one working right without an excessive amount of research, work, and testing.  There's nothing special about laminar flow and people waste way too much time trying to achieve it.  

The "Portable Laminar Flow Hood by antoniraj" in your guide will rather obviously not achieve laminar flow.  The filter must be the entire size of the workspace to get that.  The border around the filter on your pics will create a pocket of still air behind it and turbulize the air from there on out.  If you drilled pegs into the dados to have the front partly open during work it should still work fine, but isn't "laminar flow".  The plenum also doesn't seem well designed.  You need a plenum because you can't blow air directly on the filter or you will get an uneven pressure across the filter and again have turbulence and hence no laminar flow.

The design here is also not well done...

http://fradnai.free.fr/docs/doc23.pdf

This design has a few errors.  The pre-filter should be on the exhaust side of the blower.  Blowers are designed to push air, not suck it.  And you loose the utility of the pre-filter to smooth the air and prevent it from blowing directly on the HEPA filter.  The only time you should have a prefilter on the intake side is to reduce the flow of oversized blowers, and this is usually done by blocking off part of the intake rather than filtering it since filter flow changes over the life of the filter as it becomes plugged.  The design also has the blower blowing directly against a wall perpendicular to the filter, again this will cause uneven static pressure across the HEPA.  This design looks like it also has a filter smaller than the work area. Perhaps the worst part is that the blower is enclosed inside a box, which could be a fire hazard if the blower is overdriven or the prefilter clogs up.

The FreshCap design looks similar to what a lot of mycologists build, but I've never understood the focus on laminar flow.  It's extra work and there's a lot more potential problems and pitfalls. If you put sides and a sliding front on the unit you don't need laminar flow and can use much cheaper and much smaller HEPA filters.

The design I use is made just like a fume hood in reverse.  There's a furnace blower on the top pointed down, bolted to a piece of plywood.  Between the plywood and the plenum I have a layer of bedroll foam, and inset in the top of the plenum is a standard furnace filter.  The plenum is stuffed with polyfil (polypropylene pillow stuffing).  Beneath the plenum there is another layer of bedroll foam.  Two small HEPA filters are recessed into the top of the hood body about 3/4 of the way to the back and caulked into place.  They are evenly spaced side to side.  Two dados from top to bottom near the front of the work area hold a piece of plexiglass which is reinforced top and bottom with a strip of 90 degree angle aluminum running full length, minus the dado depth.  In the dados are holes every few inches that I insert a shelf peg or pin into to set the height of the plexiglass front.

The idea with the bedroll foam is to insulate the hood from blower vibrations.  None of the parts are bolted together and rely on the weight of the blower to maintain a seal between them without requiring a direct link that would transmit vibration.  The plenum only needs to be large enough to cover the HEPAs and support the blower.  Not being bolted on also makes for easy access to the filters and polyfil.  The purpose of the polyfil is both as prefilter and to smooth the airflow to the HEPAs.  You use the unit just like a fume hood with just enough handspace open in the front as is needed.

This design works well for me... inside a room in dusty warehouse.  I've verified it a number of times by exposing petri dishes of PDA in the four corners. With 5-8 min exposures I occasionally (~25%) get 1 CFU (out of  the 4 dishes).  I think this is pretty good since I'd imagine that's near the efficiency of the HEPA filter given the exposure time, amount of airflow, surface area, and input air quality.

I used to keep track of contam rate, but it was insignificant enough that I stopped.  I switched to a method where I expose a dish over the course of one block of hood work.  That way I can estimate the air quality for each batch of work.  I keep the dish while the work grows out to make sure there's no problem.

You can use a standalone HEPA filter to help clean the room air, but it also works well to just run the hood for awhile before beginning work.

I wrote a little also in this post...

https://groups.google.com/forum/#!topic/diybio/w2Fonkyangc

Not sure if you have UV in the DIY guide, but I mention the tubes I use there.

On Monday, April 18, 2016 at 3:03:33 AM UTC-7, bostjan wrote:

Hi Jake,

thanks for the feedback and ideas. I will definitely have to go through the text again (or maybe a few times) and make formatting coherent, especially for the decimal point! 

Also adding the overhead stirrer seems a good idea, I will add it to the list. Since I never used it before, do you have experience on how to hande it in combination with other devices? I see how its a major improvement when combined with a hot plate, but I imagine it would be somewhat of a hindrance when used with a pH meter?

Adding simple alternatives is also a great idea, I will work on that. If you have more suggestions, please let me know =)

Best wishes,

Boštjan

Dne ponedeljek, 18. april 2016 01.05.46 UTC+2 je oseba Jake napisala:

Wow!  Great resource!  Looks like a lot of well spent time and effort went into this.  Thank you.

A couple suggestions... I'd try to make it less confusing to worldwide audiences by using USD instead of Euros and using the decimal point "." as the decimal separator.  Currently it seems to be a bit of a mix.

It's kind of hard to read "usually in sizes for 0,5, 1,5, or 2ml and falcons (conical centrifuge tubes)".

You might suggest overhead stirring as an easier alternative to magnetic stir plates.  It's relatively easy and a lot cheaper to use a regular burner/hot plate with an overhead stirring apparatus.

Another helpful addition might be sections on techniques to get around the use of expensive equipment.  I've actually seen smart people mentally stumped by the lack of, or waste time waiting for, a stir plate.  That might seem silly, but a picture of a stir rod might actually save a few people some effort or expense.

On Sunday, April 17, 2016 at 7:31:44 AM UTC-7, bostjan wrote:

Hello everyone!

This is my first post, so let me introduce myself shortly, I'm Boštjan and while a trained Biologist, I'm new in the DIY bio community. I work at IRNAS Institute, where we are setting up an open biolab/biohackspace, which is located in Maribor (Slovenia). Together with my colleagues (who are mainly engineers) we are setting out to develop DIY lab equipment, which will be comparable to the commercial props in terms of functionality, but much more affordable. To not "reinvent warm watter", we started making a review of existing DIY equipment and how it compares to the commercial counterparts, whether it is feasible to make etc. 

You can find it on github: https://github.com/symbiolab/bio-labware/blob/master/000_bio-labware_overview.md

Hopefully we will soon be able to publish some designs of our own. The review is not completely finished yet, but with the development of DIYware, let's hope it never is. In any case, maybe some of you will find it interesting, I know that there are many collections of DIY stuff available already, however, we tried to structure it a little in terms of methodology and add some context. I would very much appreciate any comments and suggestions for improvement, as we probably missed some things and perhaps misrepresented others. I wish you all a very pleasant weekend!

Cheers,

Boštjan